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  • pharmacokinetics  (777)
  • Angiosperms
  • Springer  (1,013)
  • 1995-1999  (288)
  • 1990-1994  (725)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Risk analysis 19 (1999), S. 711-726 
    ISSN: 1539-6924
    Keywords: variability ; exposure ; susceptibility ; risk assessment ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper reviews existing data on the variability in parameters relevant for health risk analyses. We cover both exposure-related parameters and parameters related to individual susceptibility to toxicity. The toxicity/susceptibility data base under construction is part of a longer term research effort to lay the groundwork for quantitative distributional analyses of non-cancer toxic risks. These data are broken down into a variety of parameter types that encompass different portions of the pathway from external exposure to the production of biological responses. The discrete steps in this pathway, as we now conceive them, are: •Contact Rate (Breathing rates per body weight; fish consumption per body weight) •Uptake or Absorption as a Fraction of Intake or Contact Rate •General Systemic Availability Net of First Pass Elimination and Dilution via Distribution Volume (e.g., initial blood concentration per mg/kg of uptake) •Systemic Elimination (half life or clearance) •Active Site Concentration per Systemic Blood or Plasma Concentration •Physiological Parameter Change per Active Site Concentration (expressed as the dose required to make a given percentage change in different people, or the dose required to achieve some proportion of an individual's maximum response to the drug or toxicant) •Functional Reserve Capacity–Change in Baseline Physiological Parameter Needed to Produce a Biological Response or Pass a Criterion of Abnormal Function Comparison of the amounts of variability observed for the different parameter types suggests that appreciable variability is associated with the final step in the process–differences among people in “functional reserve capacity.” This has the implication that relevant information for estimating effective toxic susceptibility distributions may be gleaned by direct studies of the population distributions of key physiological parameters in people that are not exposed to the environmental and occupational toxicants that are thought to perturb those parameters. This is illustrated with some recent observations of the population distributions of Low Density Lipoprotein Cholesterol from the second and third National Health and Nutrition Examination Surveys.
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  • 2
    ISSN: 1539-6924
    Keywords: MeHg ; pharmacokinetics ; PBPK model ; variability ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract An analysis of the uncertainty in guidelines for the ingestion of methylmercury (MeHg) due to human pharmacokinetic variability was conducted using a physiologically based pharmacokinetic (PBPK) model that describes MeHg kinetics in the pregnant human and fetus. Two alternative derivations of an ingestion guideline for MeHg were considered: the U.S. Environmental Protection Agency reference dose (RfD) of 0.1 μg/kg/day derived from studies of an Iraqi grain poisoning episode, and the Agency for Toxic Substances and Disease Registry chronic oral minimal risk level (MRL) of 0.5 μg/kg/day based on studies of a fish-eating population in the Seychelles Islands. Calculation of an ingestion guideline for MeHg from either of these epidemiological studies requires calculation of a dose conversion factor (DCF) relating a hair mercury concentration to a chronic MeHg ingestion rate. To evaluate the uncertainty in this DCF across the population of U.S. women of child-bearing age, Monte Carlo analyses were performed in which distributions for each of the parameters in the PBPK model were randomly sampled 1000 times. The 1st and 5th percentiles of the resulting distribution of DCFs were a factor of 1.8 and 1.5 below the median, respectively. This estimate of variability is consistent with, but somewhat less than, previous analyses performed with empirical, one-compartment pharmacokinetic models. The use of a consistent factor in both guidelines of 1.5 for pharmacokinetic variability in the DCF, and keeping all other aspects of the derivations unchanged, would result in an RfD of 0.2 μg/kg/day and an MRL of 0.3 μg/kg/day.
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  • 3
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    Journal of molecular evolution 43 (1996), S. 399-404 
    ISSN: 1432-1432
    Keywords: Asarum ; Dioscorea ; Angiosperms ; Evolution ; Legumins ; Seed proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of legumin-encoding cDNAs fromDioscorea caucasica Lipsky (Dioscoreaceae) and fromAsarum europaeum L. (Aristolochiaceae) shows that there is an especially methionine-rich legumin subfamily present in the lower angiosperm clades including the Monocotyledoneae. It is characterized by a methionine content of 3–4 mol% which is roughly triple the methionine proportion of most other legumins. These “MetR” legumins, if present, still have to be detected in the higher angiosperms including the important seed crops. Evolutionary analysis suggests that the MetR legumins are the result of a gene duplication allowing the differentiation of legumin genes according to their sulfur content. The duplication event must have taken place before the split into mono- and dicotyledonous plants but probably after the separation of angiosperms and gymnosperms.
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  • 4
    ISSN: 1432-1432
    Keywords: Chloroplast 4.5S rRNA ; Cytosolic and chloroplast 5S rRNAs ; 5.8S rRNA ; 18S rRNA ; Nucleotide sequences ; Phylogenetic trees ; Angiosperms ; Gymnosperms ; Monocotyledons ; Dicotyledons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Complete or partial nucleotide sequences of five different rRNA species, coded by nuclear (18S, 5.8S, and 5S) or chloroplast genomes (5S, 4.5S) from a number of seed plants were determined. Based on the sequence data, the phylogenetic dendrograms were built by two methods, maximum parsimony and compatibility. The topologies of the trees for different rRNA species are not fully congruent, but they share some common features. It may be concluded that both gymnosperms and angiosperms are monophyletic groups. The data obtained suggest that the divergence of all the main groups of extant gymnosperms occurred after the branching off of the angiosperm lineage. As the time of divergence of at least some of these gymnosperm taxa is traceable back to the early Carboniferous, it may be concluded that the genealogical splitting of gymnosperm and angiosperm lineages occurred before this event, at least 360 million years ago, i.e., much earlier than the first angiosperm fossils were dated. Ancestral forms of angiosperms ought to be searched for among Progymnospermopsida. Genealogical relationships among gymnosperm taxa cannot be deduced unambiguously on the basis of rRNA data. The only inference may be that the taxon Gnetopsida is an artificial one, andGnetum andEphedra belong to quite different lineages of gymnosperms. As to the phylogenetic position of the two Angiospermae classes, extant monocotyledons seem to be a paraphyletic group located near the root of the angiosperm branch; it emerged at the earliest stages of angiosperm evolution. We may conclude that either monocotyledonous characters arose independently more than once in different groups of ancient Magnoliales or that monocotyledonous forms rather than dicotyledonous Magnoliales were the earliest angiosperms. Judging by the rRNA trees, Magnoliales are the most ancient group among dicotyledons. The most ancient lineage among monocotyledons leads to modern Liliaceae.
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  • 5
    ISSN: 1432-1432
    Keywords: CpG suppression ; GC content ; Angiosperms ; Isochores ; GC bias ; Mutational pressure ; Error-prone repair ; Transcriptionally coupled repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nuclear protein coding sequences from gymnosperms are currently scarce. We have determined 4 kb of nuclear protein coding sequences from gymnosperms and have collected and analyzed 〉60 kb of nuclear sequences from gymnosperms and nonspermatophytes in order to better understand processes influencing genome evolution in plants. We show that conifers possess both biased and nonbiased genes with respect to GC content, as found in monocots, suggesting that the common ancestor of conifers and monocots may have possessed both biased and nonbiased genes. The lack of biased genes in dicots is suggested to be a derived character for this lineage. We present a simple but speculative model of land-plant genome evolution which considers changes in GC bias and CpG frequency, respectively, as independent processes and which can account for several puzzling aspects of observed nucleotide frequencies in plant genes.
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  • 6
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    Sexual plant reproduction 5 (1992), S. 86-88 
    ISSN: 1432-2145
    Keywords: Sex chromosome markers ; Y-chromosome ; Angiosperms ; Silene latifolia ; Melandrium album
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to obtain markers for the Y chromosome ofSilene latifolia, we pooled equal weights of leaf tissue from 18 female siblings into one sample and repeated the process with 18 male siblings. Pooling was intended to provide a common genetic background for each sample, leaving the absence or presence of the Y chromosome as the primary difference between the two samples. DNA was extracted from each sample and subjected to polymerase chain reaction (PCR) amplification with arbitrary 10 bp primers. Four of 60 primers used gave an amplification with the male DNA not found among those from the female DNA. Each of these was subsequently shown to provide a reliable marker for the Y chromosome.
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  • 7
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    European journal of clinical pharmacology 42 (1992), S. 101-105 
    ISSN: 1432-1041
    Keywords: Rufloxacin ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma and urine kinetics of rufloxacin were assessed in healthy volunteers after single (100, 200, 400 and 800 mg) and multiple (300 mg followed by 150 mg daily, Group 1, and 400 mg followed by 200 mg daily, Group 2) oral doses. The kinetics of a single oral dose of 800 mg was assessed in fasting and non-fasting subjects to assess the influence of food intake on drug absorption. The AUCs were 134, 266 and 375 μg · h · ml−1 after 100, 200 and 400 mg, respectively. The AUC after 800 mg p. o. was 715 μg · h · ml −1 in fasting subjects and 614 μg · h · ml−1 in non-fasting subjects. The parameters of the model and the mean renal clearance values indicated some departure from linearity in rufloxacin kinetics. After multiple doses the plasma drug levels during the 6th treatment day were similar to those after the first dose in Group 1 and were about 30–40% higher after the first dose in Group 2. The half-lives after the last dose were much shorter than those estimated in the single dose studies (33–36 h and 50–80 h, respectively).
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  • 8
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    European journal of clinical pharmacology 42 (1992), S. 535-538 
    ISSN: 1432-1041
    Keywords: Meropenem ; Carbapenem ; pharmacokinetics ; uraemia ; haemodialysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of IV meropenem (500 mg over 30 min) has been studied in 6 healthy volunteers and 26 patients with various degrees of renal impairment. Blood samples were taken at different times over 24 h in healthy subjects and 36 to 48 h in uraemic patients, and four or five urine samples were collected over 24 or 48 h. Meropenem concentrations in plasma and urine were measured by a microbiological assay. The mean peak plasma concentration of meropenem ranged from 28 to 40 μg·ml−1 and was not affected by the degree of renal impairment. The terminal half-life of meropenem was approximately 1 h in subjects with normal kidney function and it was proportionately increased as renal function decreased. A significant linear relationship between total body clearance and creatinine clearance as well as between renal clearance and creatinine clearance was observed. The mean apparent volume of distribution at steady state was not significantly altered in uraemic patients. The mean cumulative urinary recovery of meropenem in healthy volunteers was 77% of the administered dose and it was significantly decreased in patients with renal impairment. Haemodialysis shortened the elimination half-life, from 9.7 h during the predialysis period to 1.4 h during the dialysis period. The dose of meropenem should be reduced in relation to the decrease in creatinine clearance.
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  • 9
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    European journal of clinical pharmacology 42 (1992), S. 559-560 
    ISSN: 1432-1041
    Keywords: Mefloquine ; Thai subjects ; pharmacokinetics ; Primaquine ; drug interaction ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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  • 10
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    European journal of clinical pharmacology 39 (1990), S. 395-397 
    ISSN: 1432-1041
    Keywords: atropine ; exercise ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Seven healthy males (19–32 y) underwent each of four separate conditions in a repeated measures design. Five of these subjects underwent an additional trial. In four of five trials subjects received 2.0 mg atropine sulfate intramuscularly in the anterolateral portion of the left thigh: at rest (T1); following completion of a single exercise (Ex) bout (T2), (Each bout consisted of 25 min of stationary cycling at 40% VO2 max with 5 min of seated rest), prior to three Ex bouts (T3) and following one and prior to three Ex bouts (T5). Trial 4 (T4) was the same as T3 with the substitution of a saline placebo. Serum samples were collected over a 12 h period and atropine concentration was determined by RIA. Ex trials were compared to T1. Ex prior to atropine (T2) significantly decreased the mean volume of distribution (Vz, 278 vs 2321). Ex in T3 significantly decreased the serum half life (t1/2, 4.2 vs 3.5 h), Vz (278 vs 1981), and clearance (CL, 763 vs 638 ml·min−1) and significantly increased the peak concentration (Cp, 6.7 vs 12.3 ng·ml−1) and area under the curve (AUC, 44.1 vs 53.1 ng·ml−1). In T5, Ex significantly decreased the t1/2 (3.4 h), Vz (182 l) and CL (575 ml·min−1) and significantly increased the absorption rate constant (ka, 0.482 vs 1.1 min−1), elimination rate constant (ke, 0.0012 vs 0.0015 min−1), Cp (14 ng·ml−1) and AUC (53.3 ng·h·ml−1). These results demonstrate that moderate Ex either prior to and/or immediately following drug administration has the capacity to significantly modify atropine pharmacokinetics.
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  • 11
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    European journal of clinical pharmacology 42 (1992), S. 689-691 
    ISSN: 1432-1041
    Keywords: Diphemanil methylsulphate ; pharmacokinetics ; healthy subjects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic parameters of oral diphemanil methylsulphate have been evaluated in six healthy male volunteers. Absorption of the drug was slow (tmax=2 to 4 h), the mean half-life was 8.35 h, and the amount of the drug recovered in urine within 48 h ranged from 0.6 to 7.4% of the administered dose. The results suggest low bioavailability, assuming that the drug is poorly metabolized.
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  • 12
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    European journal of clinical pharmacology 42 (1992), S. 693-694 
    ISSN: 1432-1041
    Keywords: Loperamide ; loperamide oxide ; diarrhoea ; pharmacokinetics ; dose-proportionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of loperamide, after oral administration of increasing doses (1 to 16 mg) of loperamide oxide, has been investigated in 10 healthy male volunteers, using a randomised cross-over design. Comparison of the maximum plasma loperamide concentration and AUC demonstrated that the bioavailability of loperamide was proportional to the dose of loperamide oxide administered.
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  • 13
    ISSN: 1432-1041
    Keywords: Alpidem ; Anxiolytics ; pharmacokinetics ; tolerance ; metabolites ; sedation ; adverse events
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a double-blind, placebo-controlled, crossover experiment in 21 healthy male volunteers, aged 19 to 27 y, the pharmacokinetics and tolerance of the new anxiolytic drug alpidem (SL80.0342) and its three major metabolites were studied after single doses of 25, 50, 100 and 200 mg. Plasma concentrations of alpidem (in 20 subjects) and metabolites (in 6 subjects) were measured by HPLC over a period of 54 h after dosing. Cmax, tmax and AUC(0–54) and, when possible, t1/2 were determined for alpidem and metabolites and the dose linearity of the parameters was investigated. The time to peak of alpidem was dose independent in most subjects and was short (1–4 h); the mean values at the four dosing levels were 1.9, 1.7, 1.6 and 1.8 h. The peak concentration increased with the dose, the mean values being 17, 34, 88 and 115 ng · ml−1, respectively. In 50% of the subjects cmax tended to stabilize between the 100 and 200 mg dose. Dose linearity was also present for the AUC, which plateaued between the 100 and 200 mg dose in only 3 out of 20 subjects; the mean AUC was 119, 281, 669 and 1117 ng · ml−1 · h, respectively. The apparent half-life of elimination appeared to be dose independent, mean values at the increasing dosing levels being 18.7, 19.9, 18,1 and 17.9 h. A similar relationship between the kinetics parameters and dose of the alpidem was observed for the metabolites SL83.0912, SL80.0522 and SL83.0725. The formation of metabolites was not saturated as their AUCs relative to corresponding alpidem AUCs were not dose related. Thus the kinetics of alpidem and its three major metabolites were linear after doses of 25 to 200 mg. The drug was well tolerated by most of the subjects. Sedation and dizziness occurred mainly after the 100 and 200 mg doses.
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  • 14
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    European journal of clinical pharmacology 43 (1992), S. 67-75 
    ISSN: 1432-1041
    Keywords: Morphine ; Patient-controlled analgesia ; opioids ; pharmacokinetics ; bolus-elimination-transfer ; computer-assisted continuous infusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Bone marrow transplant patients having severe, prolonged oral mucositis pain (expected to last for one to three weeks) used a computer-controlled infusion system to self-administer morphine for pain control. Individual patient pharmacokinetic information, derived from a pretreatment bolus morphine dose, was used in a new bolus-elimination transfer algorithm to produce rapid adjustments of steady plasma morphine concentrations when the patient requested more or less drug. We evaluated the performance characteristics (bias and precision) of this pharmacokinetically based patient-controlled analgesic infusion system (PKPCA) in a group of 15 cancer patients over six to 14 days. Although we found a three- to fivefold pharmaco-kinetic variability in the tailoring morphine dose data, the PKPCA system was free of systematic bias (insignificant overall prediction error) during the patient-controlled infusions in this study population. The absolute prediction error was 19.9% for the group on the first study day and 25.6% over the entire study period (aggregate results; 6–14 days of continuous use). Two-thirds of the patients exhibited no bias throughout the study period, and individual bias in the others was symmetrically distributed (three patients with underpredictions and two overpredicted). Magnitude of prediction error during the patient-controlled morphine infusions was not related to the magnitude of pharmacokinetic deviation of individual subjects from group parameters. Our results indicate that this PKPCA system provides accurate control of plasma morphine concentration when used by patients to self-administer opioid for prolonged pain relief continuously over 1 to 2 weeks. Use of individual pharmacokinetic information, instead of population parameters, may account for superior performance characteristic of this computer-assisted continuous drug infusion system.
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  • 15
    ISSN: 1432-1041
    Keywords: Indomethacin ; steady-state ; pharmacokinetics ; elderly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The steady-state pharmacokinetic profile of indomethacin was examined in twelve healthy volunteers (4 m, 8 f; 20–34 y) and in 12 elderly subjects (7 m, 5 f; 70–88 y). Two formulations of indomethacin were examined, providing duplicate data for each subject group. The subjects received each formulation of indomethacin (25 mg tid) for 6 days in a single blind crossover fashion. On day 7, after an overnight fast, a final 25 mg dose of indomethacin was given and plasma concentrations measured over the following 12 h. Kinetic parameters Cpmin, tmx and AUC (0–12 h) were determined. There were no differences in the pharmacokinetic parameters between young and elderly subjects or between data for the two formulations of indomethacin. AUC values (μg · ml−1 · h), for example, for the two formulations in the young subjects were 5.85 and 6.85 while the values for the elderly subjects were 6.55 and 6.50 respectively. When each treatment period was considered independently there was a significant difference between young and elderly subjects with regard to compliance. The rates of non compliance (over and under compliance) using a capsule count technique were, however, low with a mean maximum value of 5.8% being recorded for the elderly subjects.
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  • 16
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    European journal of clinical pharmacology 41 (1991), S. 449-452 
    ISSN: 1432-1041
    Keywords: Diabetes mellitus ; Caffeine ; pharmacokinetics ; P-450 mono-oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Diabetes may alter the pharmacokinetics of aminopyrine and antipyrine, which are used to assess liver function. Caffeine has recently been used to test liver function, but the effect of diabetes on caffeine kinetics is not known. The kinetics of caffeine has been examined in patients with decompensated Type I and Type II diabetes and in two age- and sex-matched control groups. In both types of diabetes the apparent caffeine clearance, half-life, and apparent volume of distribution were similar to controls. It is concluded that decompensated diabetes does not influence the cytochrome P-448 mono-oxygenase system responsible for caffeine metabolism.
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  • 17
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    European journal of clinical pharmacology 42 (1992), S. 231-233 
    ISSN: 1432-1041
    Keywords: Isradipine ; Haemodialysis ; pharmacokinetics ; dialysability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of isradipine, a calcium-channel blocker, have been studied in eight patients on chronic haemodialysis. A single oral dose of 5 mg was administered on both a non-haemodialysis and a haemodialysis day and the plasma concentrations of isradipine were analyzed. The mean cmax, tmax, AUC, and t1/2 in plasma on the non-haemodialysis day were 5.2 ng·ml−1, 1.4 h, 23.8 ng·h·ml−1, and 3.1 h, respectively. The dialysis clearance of isradipine was negligible (5.0 ml·min−1). The t1/2 values during haemodialysis were not significantly different from those observed during the same period post dose on the non-haemodialysis day. The study demonstrates that supplemental doses of isradipine are not necessary in these patients since isradipine is not significantly removed by haemodialysis.
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  • 18
    ISSN: 1432-1041
    Keywords: Liver cirrhosis ; Spirapril ; ACE inhibitor ; pharmacokinetics ; haemodynamic effects ; liver function tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and haemodynamic effects of orally administered spirapril, a novel angiotensinconverting enzyme (ACE) inhibitor, have been investigated in patients with liver cirrhosis (n=10), in patients with chronic, non-cirrhotic liver disease (n=8) and in a control group of healthy subjects (n=16). The absorption and elimination of spirapril did not differ between patients with liver disease and control subjects. In contrast, the bioavailability of spiraprilat, the metabolite responsible for the pharmacological action of spirapril, was significantly reduced in patients (AUC 820 μg·h·l−1, 923 μg·h·l−1 and 1300 μg·h·l−1 in patients with cirrhosis, patients with non-cirrhotic liver disease and in healthy subjects, respectively. Compared to healthy subjects, cirrhotic patients had a reduced rate constant of spiraprilat formation (1.10 h−1 in patients vs. 2.00 h−1 in control subjects) while the elimination half-life of spiraprilat was not different. The effect of spirapril on diastolic blood pressure was decreased in patients with chronic liver disease as compared to the controls. Thus, the pharmacokinetics of spirapril was unchanged in patients with different types of liver disease, including cirrhosis. However, the bioavailability of spiraprilat and hypotensive effect of spirapril were reduced in patients.
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  • 19
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    European journal of clinical pharmacology 40 (1991), S. 593-597 
    ISSN: 1432-1041
    Keywords: Dopamine ; Newborns ; critically ill patients ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Dopamine is frequently used in critically ill newborn infants for treatment of shock and cardiac failure, but its pharmacokinetics has not been evaluated using a specific analytical method. Steady-state arterial plasma concentrations of dopamine were measured in 11 seriously ill infants receiving dopamine infusion, 5–20 μg · kg−1 · min−1, for presumed or proven sepsis and hypotensive shock. Steady-state concentrations of dopamine ranged from 0.013–0.3 μg/ml. Total body clearance averaged 115 ml · kg−1 · min−1. The apparent volume of distribution and elimination half life averaged 1.8 1 · kg−1 and 6.9 min, respectively. No relationship was observed between dopamine pharmacokinetics and gestational age, postnatal age or birthweight. Substantial interindividual variation was seen in dopamine pharmacokinetics in seriously ill infants, and plasma concentrations could not be predicted accurately from its infusion rate. Marked variation in clearance explains in part, the wide dose requirements of dopamine needed to elicit clinical response in critically ill newborn infants.
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  • 20
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    European journal of clinical pharmacology 40 (1991), S. 619-624 
    ISSN: 1432-1041
    Keywords: Inulin ; pharmacokinetics ; half life ; distribution ; concentration-dependent clearance ; healthy subjects ; chronic renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of inulin was studied in 30 healthy male and 10 healthy female volunteers, and 10 patients with stable chronic renal failure (mean creatinine clearance 45 ml·min−1) following intravenous infusion of 70 mg·kg−1 over 5 min. Plasma concentrations fell rapidly initially but the rate of decline decreased continuously over 8 h and a linear terminal elimination phase could not be identified. Inulin was excreted rapidly by the subjects with normal renal function and 97.3% of the dose was recovered in the urine in 8 h. There was a progressive highly significant fall in the renal clearance of inulin after 2 h as plasma concentrations fell below about 150 mg·l−1. Six to 8 h after administration the clearance was less than 50% of the initial value in the healthy volunteers and the corresponding fall in the renal patients was 33%. The concentration-dependent renal clearance of inulin was confirmed in “step-up” and “step-down” constant infusion studies in which clearances were measured at mean plasma concentrations ranging from 35.2 to 186.7 mg·l−1. These studies virtually excluded time, changes in posture and urine flow rate as important factors. There was no statistically significant fall in clearance during the first 2 h and kinetic analysis was based on data obtained over this time. Under these conditions the mean plasma half life, volume of distribution (Vss) and total body clearance of inulin in the healthy males, healthy females and patients with chronic renal failure were 73.2, 65.5 and 172.4 min, 10.5, 9.6 and 8.81·70 kg−1 and 113.3, 111.5 and 43.3 ml·min−1·70 kg−1 respectively. There were no sex differences in any of the kinetic variables. The mechanism of the concentration-dependent clearance of inulin is unknown but the findings are consistent with saturable renal tubular reabsorption. Care is required with the use of inulin for measurement of the glomerular filtration rate by the single injection technique.
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  • 21
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    European journal of clinical pharmacology 40 (1991), S. 631-633 
    ISSN: 1432-1041
    Keywords: Mefloquine ; ampicillin ; Thai subjects ; pharmacokinetics ; enterohepatic recycling ; drug interaction ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a single oral dose of mefloquine given either alone or with ampicillin has been studied in 8 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with ampicillin (1648 vs 1228 ng·ml−1), as well as a significantly reduced terminal half life (15.3 vs 17.7 days), mean residence time (20.1 vs 23.4 days) and volume of distribution at steady state (14.1 vs 19.4 l·kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 5 days was significantly increased by ampicillin (4.86 vs 3.27 μg·ml−1 day). These changes in mefloquine disposition after antibiotic treatment may be due both to an increase in fractional bioavailability and a reduction in the enterohepatic recycling of mefloquine.
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  • 22
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    European journal of clinical pharmacology 40 (1991), S. 637-638 
    ISSN: 1432-1041
    Keywords: Roxatidine acetate ; sucraflate ; pharmacokinetics
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  • 23
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    European journal of clinical pharmacology 45 (1993), S. 357-361 
    ISSN: 1432-1041
    Keywords: Circadian rhythms ; Indomethacin ; Ketoprofen ; pharmacokinetics ; time-varying models ; nonsteroidal anti-inflammatory drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A one-compartment model with first-order absorption has provided good fits to five sets of indomethacin data and four sets of ketoprofen data taken at different times of day. There was substantial variation in the model parameters with time of administration and most of the features of this variation applied equally to both drugs. From the data examined, the source of variation appears to be mainly in the absorption phase and this was confirmed using a chronokinetic analysis, in which simultaneous fits were obtained with time-variant rate parameters. However, there may also be circadian variation in protein binding. The danger of quoting parameter values for either of these two drugs based on administration at a single time of day has been illustrated, and this may well be true for other drugs.
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  • 24
    ISSN: 1432-1041
    Keywords: Gamma-hydroxybutyric acid ; pharmacokinetics ; dose-proportionality
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Gamma-hydroxybutyric acid (GHB) is effective in treatment of the alcohol and opiate withdrawal syndromes. Its absorption and disposition kinetics have been studied in 8 healthy male volunteers following oral administration of single doses of 12.5, 25 and 50 mg kg−1. The AUC increased disproportionately with the dose and so the apparent oral clearance decreased significantly as the dose was increased, whereas the terminal half-life and mean residence time increased. The peak plasma concentrations normalised to the lowest dose fell significantly with increasing doses, whilst the corresponding peak times increased. These findings suggest that both the oral absorption and the elimination of GHB are capacity-limited processes. GHB did not bind to significant extent to plasma proteins over the therapeutic concentration range. The pharmacokinetic parameters in healthy volunteers were not significantly different from those previously observed in alcohol-dependent patients with compensated alcoholic liver disease.
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  • 25
    ISSN: 1432-1041
    Keywords: Glyceryl trinitrate spray ; pharmacokinetics ; a/b-ratio ; pulmonary artery diastolic pressure ; finger pulse curve ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time course and the magnitude of the effect of glyceryl trinitrate (GTN) on central venous (pulmonary artery diastolic pressure-PAPd) and peripheral arterial (a/b-ratio of the finger pulse wave) haemodynamics were compared in a randomized double-blind cross-over study in 12 patients suffering from congestive heart failure (NYHA II–III) with elevated PADd at rest (≥15 mm Hg). The data were obtained in a bioavailability study of two sprays of glyceryl trinitrate, which differed in their galenical characteristics and in the dose of GTN (0.4 mg vs. 0.8 mg). Following sublingual administration of each spray, PAPd, a/b-ratio and the plasma concentrations of GTN and its metabolites were measured up to 30 min. The relative bioavailability of GTN of the test preparation was estimated to be 157%, 161% and 147%, when calculated from the plasma concentration-time data or the integrated effect of GTN on a/b-ratio or PAPd, respectively. The mean time courses of the decrease in PAPd and the increase in the a/b-ratio of the finger pulse curve were mirror images. Thus, there was a strong correlation between the mean values of PAPd and a/b-ratio following the administration of glyceryl trinitrate. Since the slope of the relationship differed considerably between the patients, the magnitude of effect of GTN on PAPd in the individual patient could not be predicted from the changes in a/b-ratio.
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  • 26
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    European journal of clinical pharmacology 44 (1993), S. 463-466 
    ISSN: 1432-1041
    Keywords: Benazepril ; Proteinuria ; benazeprilat ; ACE inhibitor ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have investigated whether the pharmacokinetics and pharmacodynamics of the ACE inhibitor benazepril hydrochloride are altered with proteinuria by studying 8 patients with major proteinuria of different causes who were given a single dose of 10 mg p.o. The maximum plasma concentration of benazepril was found between 0.5 and 2 h after dosing (median 1 h). Its elimination was almost complete within 6 h. Peak plasma levels of benazeprilat, the active metabolite of benazepril, were observed between 1 and 6 h (median 2.5 h). The elimination of benazeprilat from plasma was biphasic, with mean initial and terminal half-lives of 3.0 and 17.3 h, respectively. On average, the pharmacokinetic parameters of benazepril and benazeprilat in the patients did not differ from those in a historical control group of healthy volunteers, but intersubject variability in the AUC and half-lives of benazeprilat was greater in the patients. Plasma ACE was completely inhibited from 1.5 to 6 h after dosing, and at 48 h the mean inhibition was still 42 %. Plasma renin showed substantial intersubject variation. Mean supine blood pressure (systolic/diastolic) was reduced from baseline by a maximum of 18/13 mm Hg at 6 h. Proteinuria was diminished after benazepril in 7 patients. In conclusion, the results of this study suggest that proteinuria in the nephrotic range does not require a change in benazepril dosage.
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  • 27
    ISSN: 1432-1041
    Keywords: dDAVP ; bioavailability ; gastrointestinal tract ; healthy volunteers ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute bioavailability of an aqueous solution of 1-deamino-8-D-arginine vasopressin (dDAVP) from different regions of the gastrointestinal (GI) tract (stomach, duodenum, jejunum, ileum, colon, rectum) has been studied in 6 healthy, male volunteers aged 24 to 35 years, followed for 12 h after each drug administration. For i. v. administration the subjects received 4 μg dDAVP. For intestinal administration 400 μg dDAVP was directly applied to six distinct sites in the GI tract via two or four channel tubes with or without a distal occlusive balloon. Biological effects were assessed and plasma and urinary levels of dDAVP were measured using a specific, sensitive RIA. Urine osmolality remained elevated and diuresis decreased for 12 h following dDAVP administration irrespective of the site of application. After i. v. administration, the half-life of elimination of dDAVP was 60.0 min, plasma clearance 1.7 ml·min−1·kg−1, amount excreted in urine 2.0 μg and renal clearance was 0.8 ml·min−1·kg−1. The mean bioavailability (f) after gastric application was 0.19% (range 0.02–0.35%). f was 0.24% after duodenal application (range 0.04–0.62%), 0.19% after jejunal (range 0.01–0.41%), 0.03% after distal ileal (range 0.01–0.08%), 0.04% after proximal colonic (range 0.01–0.12%) and 0.04% after rectal (0.01–0.10%) application. The bioavailability was significantly higher in the three upper GI regions in comparison to the three lower regions. The bioavailability of dDAVP after gastric, duodenal and jejunal application was similar to that after swallowing a tablet in a previous study. Absorption from the ileum was lower than expected and no preferential site of absorption was found.
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  • 28
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    European journal of clinical pharmacology 42 (1992), S. 171-174 
    ISSN: 1432-1041
    Keywords: Quinine ; Malaria ; pharmacokinetics ; red blood cells ; plasma ; saliva ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of quinine has been studied in ten healthy adult Africans after intravenous infusion and oral ingestion of a 500 mg dose. Blood and saliva samples were collected over 48 h and quinine in plasma, red cells and saliva was determined by HPLC. Quinine was rapidly and almost completely absorbed after an oral dose, with absorption half-life of 0.53 h, a tmax of 1–3 h and a bioavailability of 88%. Analysis of the i. v. data gave an apparent volume of distribution of 3.6 1·kg−1 and a plasma clearance of 0.19 l·kg−1·h−1. The concentration-time curves for plasma, red cells and saliva had declining phases were approximately parallel, giving a similar half-life that in all three media. The half-lives after the i. v. infusion also did not different from those after oral administration. The dose was well tolerated by both methods of administration.
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  • 29
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    European journal of clinical pharmacology 42 (1992), S. 175-179 
    ISSN: 1432-1041
    Keywords: 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) ; Triflusal ; triflusal metabolite (HTB) ; pharmacokinetics ; protein binding ; ultrafiltration ; binding constant
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) is the main active metabolite of the platelet anti-aggregant drug triflusal. Its binding to plasma proteins of rats and healthy volunteers in vitro and in vivo has been studied. Rats were given a single oral dose of 50 mg·kg−1 triflusal and the healthy volunteers received 300 mg as a single oral dose or a multiple dose regimen of 600 mg every 24 h and 300 mg every 8 h, both for 13 days. Protein-free HTB was obtained by ultrafiltration. Unbound and total HTB concentrations were determined by HPLC. HTB was primarily bound to albumin in plasma. The Scatchard plots suggested two types of binding sites for HTB on the albumin molecule. In rats, the binding constants (K=intrinsic affinity constant, n=number of binding sites) were K1=1.4×105 l·mol−1, n1=1.23, and K2=4.1×103 l·mol−1 and n2=3.77. The mean plasma concentration in rats after oral administration was 185 (37) μg·ml−1 (protein-free HTB: 2.44 (0.77)%). The binding constants in human plasma were K1=4.7×105 l·mol−1, n1=1.93, K2=4.3 l·mol−1 and n2=4.28. The plasma HTB concentration in man (n=8) was 35 μg·ml−1 (Cmax) after a single oral dose of triflusal 300 mg, 172.96 μg·ml−1 (Cmax·ss) during the multiple dosage regimen of 300 mg every 8 h, and 131 μg·ml−1 (Cmax·ss) during the multiple oral dose regimen of 600 mg every 24 h. Unbound HTB ranged from 0.27 to 0.43%, depending on dose. HTB had high affinity for plasma albumin, which was not saturable after therapeutic doses. It showed linear elimination.
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  • 30
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    European journal of clinical pharmacology 42 (1992), S. 181-185 
    ISSN: 1432-1041
    Keywords: Glycerol ; brain oedema ; serum ; cerebrospinal fluid ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Glycerol 50 g infused i. v. over 2 to 6 h is widely used to treat cerebral oedema in patients with acute stroke. Its transit through the blood-cerebrospinal fluid barrier in subjects with uninflamed meninges has now been examined. In 7 patients with an external ventriculostomy for occlusive hydrocephalus, each of whom was given 500 ml of a 10% solution IV over 4 h, serum and CSF were repeatedly sampled during and after the infusion and glycerol was measured enzymatically. The highest serum glycerol level of 191–923 mg/l was observed at the end of the infusion. The maximum CSF glycerol of 18.7–110.8 mg/l was attained 0–1 h after the end of the infusion. Elimination both from serum and CSF approximated a single-exponential decay; the elimination half-life from serum was 0.29–0.56 h compared to 1.03–3.68 h from CSF. In six of the seven cases there was a temporary reversal of the serum/CSF concentration gradient during glycerol elimination. The ratios of the AUCs of CSF and serum, which describe the overall penetration of glycerol into CSF, ranged from 0.09–0.31. In conclusion, the serum level of glycerol produced by giving 50 g IV glycerol over 4 h may not be sufficiently high reliably dehydrate to brain tissue in many patients, and the slow elimination of glycerol from the CSF may be related to the so-called rebound phenomenon.
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  • 31
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    European journal of clinical pharmacology 42 (1992), S. 187-191 
    ISSN: 1432-1041
    Keywords: Dipyrone ; Acetylation phenotype ; metabolism ; pharmacokinetics ; urinary excretion ; metabolite clearance
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The formation and urinary excretion of the dipyrone metabolites, methylaminoantipyrine (MAA), aminoantipyrine (AA), formylaminoantipyrine (FAA) and acetylaminoantipyrine (AAA) were determined following administration of a single oral 1.0 g dose of dipyrone to 12 healthy volunteers. The AAA/AA plasma ratio showed that 3 subjects were slow and 9 were rapid acetylators. Pharmacokinetic parameters were determined separately for each group. A good correlation was found between the plasma and urine AAA/AA ratios. The renal clearance of the four metabolites was similar for both phenotypes. A significant difference in the rate of formation of dipyrone metabolites was found for AA, 0.25 (slow) vs 0.1 ml·min−1·kg−1 (rapid), and for AAA 0.75 (slow) vs 7.53 ml·min−1·kg−1 (rapid). There were comparable differences between slow and rapid acetylators in the AUC and the urinary excretion extrapolated to infinity for AA and AAA. The present results show that the kinetics of dipyrone metabolites in plasma and urine can provide a useful measure of the activity of the enzymes involved in their production.
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  • 32
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    European journal of clinical pharmacology 42 (1992), S. 197-201 
    ISSN: 1432-1041
    Keywords: Digoxin ; Salbutamol ; serum ; skeletal muscle digoxin ; pharmacokinetics ; drug interaction ; serum potassium
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single dose of the β2-adrenoceptor agonist salbutamol has previously been shown to decrease serum digoxin concentration in healthy volunteers. A possible explanation of the phenomenon is a β2-adrenoceptor-mediated increase in the specific binding of digoxin to skeletal muscle. The present study was undertaken to further elucidate the effect of salbutamol on the pharmacokinetics of digoxin in man. Nine volunteers were studied on two occasions during salbutamol or placebo treatment. On test days salbutamol, 4 μg·kg−1·h−1 or saline was infused for 10 h, preceded and followed by four and three days, respectively, of oral administration. A single i. v. injection of digoxin 15 μg·kg−1, was given 20 min after starting the infusion. At the end of the infusion a muscle biopsy was taken from the vastus lateralis. Blood samples for the analysis of serum digoxin and potassium were repeatedly taken over 72 h. Urine was collected over a period of 24 h for determination of the renal excretion of digoxin and potassium. The serum digoxin concentration, expressed as the AUC 0–6 h was 15% lower during salbutamol infusion than during saline infusion. Salbutamol caused significantly faster elimination of digoxin from the central volume of distribution to deeper compartments. Salbutamol had no effect on the renal clearance of digoxin. The skeletal muscle digoxin concentration tended to be higher (48%) during salbutamol compared to placebo treatment. The serum potassium concentration was significantly lower after salbutamol compared to placebo, as was the rate of renal excretion of potassium. The results support the hypothesis that the salbutamol-induced decrease in serum digoxin is caused by increased distribution of digoxin to skeletal muscle (and possibly other tissues), and that this may be secondary to a β2-adrenoceptor-mediated increase in Na-K-ATPase activity.
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  • 33
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    European journal of clinical pharmacology 42 (1992), S. 203-207 
    ISSN: 1432-1041
    Keywords: Nicorandil ; pharmacokinetics ; angina pectoris ; uraemia ; adverse effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of oral nicorandil 20 mg 12 hourly for 9 doses was evaluated in 21 hospitalized patients with angina pectoris due to coronary heart disease and with normal and impaired renal function. Patients were divided into 3 groups based on creatinine clearance (CLCr): GROUP I (n=6) 〉 80 ml/min, GROUP II (n=8) 20–80 ml/min, and GROUP III (n=7) 〈 20 ml/min. After the first dose, the total clearance of nicorandil (CL) value did not change with increasing renal failure and so was not dependent on creatinine clearance. After the last dose CL was 51 l·h−1 in Group I, 44 l·h−1 in Group II and 56 l·h−1 in Group III, and it was not related to creatinine clearance. The percentage of the dose excreted in the urine was 0.4%. No significant difference was noted in any of the other pharmacokinetic parameters examined in the three groups, not even on comparing values obtained on the first and last days of treatment. The findings suggest that there is no need to change the dose of nicorandil in subjects with different degrees of renal failure.
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  • 34
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    European journal of clinical pharmacology 46 (1994), S. 83-85 
    ISSN: 1432-1041
    Keywords: Enuresis ; Oxybutynine chloride ; children ; pharmacokinetics ; adverse effects ; anticholinergic actions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Anticholinergic adverse-effects in children treated with conventional doses of oxybutynine led us to measure plasma oxybutynine levels in children. 18 children, aged 5 to 13 y, who required treatment with oxybutynine chloride for daytime incontinence were studied. Plasma concentrations were measured on the fifth day of a course of treatment in which the dose was adapted to the child's body weight; the dose was given twice daily at 12-hour intervals. In 10 children aged between 5 and 8 y, the mean dose was 0.1 mg · kg−1. In 8 children aged between 10 and 13 years, the mean dose was 0.15 mg · kg−1. The highest concentration was usually found between 1 and 2 h after administration. The subsequent fall in concentration was rapid and after 6 h oxybutynine was no longer measurable in 14 of the children. The concentrations found were not different from those seen in adults given equivalent doses. The results show that plasma concentrations in children were not very different from those observed in adults if the dose were adapted to the body weight of the children. No special differences in paediatric use were revealed that might explain the particular adverse-effects. The results of the study argue against the dosage regimen proposed before these adverse events were detected. They strongly favour a dose adapted to the body weight of the child, with a 12-hour interval between doses.
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  • 35
    ISSN: 1432-1041
    Keywords: Steroid 5α-reductase inhibitor ; Testosterone metabolism ; MK-0434 ; pharmacodynamics ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract A four-period, two-panel, single-rising-dose study (0.1–100 mg) was conducted in healthy males to investigate the pharmacodynamics, tolerability and pharmacokinetics of MK-0434, a steroid 5α-reductase inhibitor. MK-0434 was associated with a significant reduction in dihydrotestosterone, which was maximal at 24 h and maintained through 48 h post treatment. The maximum reduction was approximately 50 % and occurred at all doses above 5 mg (10, 25, 50 and 100 mg). MK-0434 appeared to have no effect on serum testosterone at these single doses. Rising single doses of MK-0434 were associated with an increase in Cmax and AUC but the changes were less than proportional to dose, most likely due to nonlinear absorption. MK-0434 given in single doses up to 100 mg was without significant adverse effects in healthy male volunteers. In summary, MK-0434 is a well-tolerated, potent, orally active 5α-reductase inhibitor in man.
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  • 36
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    European journal of clinical pharmacology 46 (1994), S. 261-265 
    ISSN: 1432-1041
    Keywords: Cystic fibrosis ; Cyclosporin ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Cyclosporin (CsA) is currently the main immunosuppressive agent used in organ transplantation with considerable improvement in graft survival. Oral CsA solution is highly lipophilic, and its bioavailability may be reduced in cystic fibrosis (CF) heart-lung transplant recipients with pancreatic, gastrointestinal, and hepatic insufficiency. The bioavailability of oral CsA solution in 7 CF transplant recipients (5 male and 2 female with a mean age of 27 years and a mean weight of 49 kg) and 3 non-CF heart-lung recipients (1 male and 2 female with a mean age of 41 years and a mean weight of 60 kg) was studied. Following intravenous CsA administration, the kinetic curves were similar with no significant difference in the volume of distribution and clearance of CsA demonstrated between the CF and non-CF groups. The mean daily dose of oral CsA in 7 CF subjects (23.3 mg·kg−1) was significantly higher than the 3 non-CF heart-lung recipients (4.8 mg·kg−1). The mean maximum blood concentration of CsA for the oral dose was 776 ng·ml−1 for the 7 CF subjects, which was comparable with the mean peak values of 789 ng·ml−1 for the 3 non-CF control subjects. Poor enteral absorption of CsA probably accounts for the significantly lower mean bioavailability in the 7 CF subjects (14.9%) compared with the 3 non-CF control subjects (39.4%). The effects on the bioavailability of oral CsA solution by pancreatic enzymes (Creon) and histamine-2 antagonist (ranitidine) were also evaluated in the 7 CF subjects. No significant difference was demonstrated.
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  • 37
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    European journal of clinical pharmacology 44 (1993), S. 247-251 
    ISSN: 1432-1041
    Keywords: Proguanil ; Pregnancy ; Malaria ; cycloguanil ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma and whole blood concentrations of proguanil, its active metabolite cycloguanil, and the inactive metabolite 4-chlorophenyl-biguanide, were measured by HPLC in 10 healthy Karen women in the last trimester of pregnancy, following a 200 mg single oral dose of proguanil. Four of these women were restudied 2 months after delivery. The pharmacokinetic properties of proguanil were similar during and after pregnancy. Median peak plasma concentrations of proguanil during pregnancy and following delivery were 212 and 215 ng·ml−1, and occurred at 4.5 and 5 h, respectively. Mean plasma AUC values for proguanil during and following pregnancy were 94 and 98 ng·h·ml−1·kg−1, respectively. Corresponding whole blood AUC values were 361 and 396 ng·h·ml−1·kg−1. The mean elimination half lives and mean residence times of proguanil in plasma and whole blood were 12.3 and 19.6 h and 13.8 and 20.7 h respectively during pregnancy. Following pregnancy these values were 17.1 and 19.7 h for plasma and 19.7 h and 20.2 h for whole blood respectively. Mean peak plasma and whole blood concentrations of cycloguanil following pregnancy were 25 and 22 ng·ml−1 respectively. During pregnancy peak cycloguanil concentrations in both plasma and whole blood were markedly lower, 13 and 12 ng ml−1, respectively. Two pregnant women (neither of whom were restudied) were probably poor metabolisers of proguanil. The mean ratio of proguanil to cycloguanil plasma AUC was 16.7 in the third trimester of pregnancy and 7.8 following pregnancy, compared with less than 5 in previously reported studies. The concentrations of 4-chlorophenylbiguanide in both plasma and whole blood in pregnant subjects were also lower than those after pregnancy. These data show that blood concentrations of the active antimalarial metabolite cycloguanil are reduced in late pregnancy and that the currently recommended dose of proguanil could be inadequate for antimalarial prophylaxis in pregnant women.
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  • 38
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    European journal of clinical pharmacology 44 (1993), S. 265-269 
    ISSN: 1432-1041
    Keywords: Cyclosporine ; Renal transplantation ; pharmacokinetics ; intraindividual variation ; circadian variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The intraindividual variability and circadian variation of oral cyclosporine (CsA) pharmacokinetics were studied over 24 h in 18 renal transplant recipients at steady state, and in 10 of the patients during a second 24 h period. The absolute percentage intraindividual difference in daytime AUC (0–12 h) ranged from 2% to 54% (mean 30%), and the corresponding variability in nighttime AUC (0–12 h) ranged from 5% to 80% (mean 34%). The pharmacokinetic variables t1/2, tmax and Cmax were more variable than the AUC (0–12 h) both during the day and at night. The evening trough level was significantly lower than the morning trough level; 185 ng · ml−1 versus 223 ng · ml−1. This, together with a significantly longer t1/2 in the night than the day, suggested circadian variability in the pharmacokinetics of CsA. In a separate retrospective study in 162 renal transplant recipients given CsA by constant intravenous infusion, repeated CsA blood concentration measurements at steady state showed lower concentrations during the day than the night, suggesting higher CsA clearance during daytime. It is concluded that CsA pharmacokinetics in renal transplant recipients, besides the well-known interindividual variability, also displays large intraindividual variability as well as circadian variation. Our findings further emphasize the necessity and difficulty of pharmacological monitoring in the clinical use of CsA in organ transplantation.
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  • 39
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    European journal of clinical pharmacology 44 (1993), S. 301-302 
    ISSN: 1432-1041
    Keywords: Adriamycin ; Haemodialysis ; adriamycinol ; pharmacokinetics ; moment analysis
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  • 40
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    European journal of clinical pharmacology 44 (1993), S. 305-306 
    ISSN: 1432-1041
    Keywords: Atenolol ; bioavailability ; intestinal absorption ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We investigated the dose proportionality after the intake of oral atenolol 25, 50, 100 and 150 mg. Standard tablets were taken by 8 healthy volunteers in randomised order of doses. The area under the curve divided by dose did not differ between the doses, indicating that the absorption of this hydrophilic compound, with known incomplete bioavailability, was constant over the range tested.
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  • 41
    ISSN: 1432-1041
    Keywords: Esmolol ; β1-Adrenoceptor antagonist ; tricresylphosphate ; pharmacokinetics ; effect kinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of esmolol at different rates of infusion (100, 250 and 500 μg·kg−1 BW·min−1) were compared with β-adrenoceptor occupancy (β1 and β2, estimated by a subtype selective radioreceptor assay) and plasma concentrations of esmolol and its acid metabolite were measured by HPLC. Up to a rate of infusion of esmolol of 500 μg·kg−1 BW·min−1 there was a maximal β1-receptor occupancy of 84.7% while β2-receptor occupancy was below the detection limit; confirming the β1 selectivity of esmolol. Exercise-induced increases in heart rate and systolic blood pressure were reduced by esmolol in a dose-dependent manner. The estimated EC50 values of rate of infusion for the reduction in heart rate and systolic blood pressure during exercise were 113 and 134 μg·kg−1 BW · min−1, respectively. Additionally, heart rate and systolic blood pressure were reduced moderately at rest. Because of the short elimination half-life of esmolol caused by the rapid hydrolysis to its acid metabolite, 45 min after end of infusion high plasma concentrations of the metabolite (maximally 80 μg·ml−1) but no esmolol were detectable. Since no in vivo effects have been observed, despite the presence of high plasma concentrations of the metabolite, the metabolite did not participate in the observed effects up to an infusion rate of esmolol of 500 μg·kg−1 BW·min−1. The plasma concentrations of antagonist detected by radioreceptor assay and plasma concentrations of esmolol detected by HPLC showed a good correlation (r=0.97). Since the cardiovascular effects, determined before and 45 min after termination of infusion of esmolol were similar, it can be concluded that the observed effects on heart rate and systolic blood pressure are exclusively mediated by esmolol.
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  • 42
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    European journal of clinical pharmacology 49 (1996), S. 387-391 
    ISSN: 1432-1041
    Keywords: Key words Liver function tests; elderly ; pharmacokinetics ; geriatrics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The pharmacokinetics of brofaromine, a selective inhibitor of monoamine oxidase A, was evaluated in 12 frail elderly patients (66–92 y) and 12 healthy volunteers (20–35 y). Methods: Quantitative liver function tests were performed to show whether brofaromine elimination in the elderly could be predicted from noninvasive assessment of CYP1A2 activity (caffeine clearance) or liver plasma flow (sorbitol clearance). Results: In the elderly the AUC of brofaromine was significantly increased (e.g. for the 75 mg dose 43.2 vs 19.9 μmol*h⋅l−1, clearance was reduced (5.0 vs. 11.8 l⋅h−1), the volume of distribution was smaller (130 vs. 230 l), and the half-life was slightly increased (19.0 vs. 14.2 h). No significant correlation was observed between hepatic plasma flow and brofaromine clearance (r = 0.41, P = 0.05), whereas CYP1A2 activity and brofaromine clearance were tightly correlated (r = 0.94, P 〈 0.0001). Conclusion: Caffeine clearance, a simple, noninvasive test of CYP1A2 activity, is predictive of brofaromine clearance.
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  • 43
    ISSN: 1432-1041
    Keywords: Ramipril ; Piretanide ; pharmacokinetics ; pharmacodynamics ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetics and pharmacodynamics of single oral doses of 5 mg ramipril and 6 mg piretanide administered separately and in combination were determined in a single blind, randomised, 3-period cross-over study in 24 healthy male volunteers. The peak plasma concentrations of ramipril and ramiprilat increased slightly (from 11.9 to 14.8 ng/ml, and from 6.39 to 8.96 ng/ml, respectively) as did the area under the plasma concentration-time curve of ramipril (0–4 h) and ramiprilat (0–24 h) (from 15.8 to 19.8 ng·ml−1·h, and from 63.4 to 74.6 ng·ml−1·h, respectively). The urinary excretion of ramiprilat also rose (from 6.82 to 7.73 % of dose) following simultaneous treatment with piretanide. These effects were probably due to reduced first-pass metabolism of ramipril/ramiprilat to inactive metabolites. The blood pressure lowering effect, the time course of inhibition of ACE activity in plasma and the concentration-response relationship for the inhibition of plasma ACE activity were not affected by piretanide. The peak plasma concentration of piretanide was somewhat reduced (from 285 to 244 ng/ml) following simultaneous treatment with ramipril. No other pharmacokinetic parameter was affected. Piretanide increased urine flow, and sodium, chloride and potassium excretion, especially during the first 2 hours following administration. These pharmacodynamic parameters were not affected by ramipril. Thus, simultaneous administration of single oral doses of ramipril and piretanide caused modest changes in the peak and average plasma concentrations of both drugs, which did not lead to detectable alterations in the pharmacodynamic parameters measured in healthy volunteers.
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  • 44
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    European journal of clinical pharmacology 46 (1994), S. 573-574 
    ISSN: 1432-1041
    Keywords: Standard deviation ; Arithmetic mean ; pharmacokinetics
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  • 45
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    European journal of clinical pharmacology 46 (1994), S. 565-567 
    ISSN: 1432-1041
    Keywords: Phenytoin ; Saliva ; therapeutic drug monitoring ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of atropine-induced reductions in saliva flow rate on saliva phenytoin concentrations were evaluated in a randomised placebo-controlled crossover study in a group of epileptic patients stabilised on the drug. Pretreatment with atropine caused significant reductions in saliva flow rates during the first 4 h, compared to saline. The AUC0–4 h for saliva flow rate was significantly reduced by atropine (245 g vs 327 g) and the saliva phenytoin AUC0–4 h was significantly increased (5.6 μg · ml−1 · h vs 4.5 μg · ml−1 · h) without affecting plasma phenytoin concentrations. The saliva/plasma phenytoin AUC0–4 h ratio was therefore significantly increased by atropine (0.15 vs 0.12). However, there was a poor correlation between saliva/plasma phenytoin concentration ratios and saliva flow rates for the two treatments in the individual patients (correlation coefficient ranged from 0.25 to 0.65). These findings demonstrate that saliva phenytoin concentrations are increased by reductions in saliva flow rate. Caution is therefore required when saliva phenytoin concentrations are used for therapeutic monitoring in the presence of factors which may affect saliva flow rate.
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  • 46
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    European journal of clinical pharmacology 47 (1994), S. 61-65 
    ISSN: 1432-1041
    Keywords: Cyclosporine A ; kidney transplant ; nephrotic syndrome ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetic parameters of cyclosporine (CsA) were determined in 23 kidney transplant recipients and 19 children with nephrotic syndrome, after intravenous and oral administration. The mean bioavailability was 39 %, blood clearance was 0.55 l · h-1 · kg-1 and volume of distribution at steady-stade was 2.77 l · kg-1. The absorption profile was monophasic (67 %), biphasic (29 %) or poor (4 %). The maximum blood concentration of CsA was significantly higher in children with a monophasic profile than in children with a biphasic profile (550 vs 380 ng · ml-1). Blood clearance was significantly higher in the transplant recipients than in the patients with nephrotic syndrome (0.65 vs 0.43 l · h-1 · kg-1. Although age, haematocrit, creatinine clearance, serum albumin and cholesterol differed between the two groups, only haematocrit and creatinine clearance were significantly (negatively) correlated with CsA clearance.
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  • 47
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    European journal of clinical pharmacology 47 (1994), S. 81-84 
    ISSN: 1432-1041
    Keywords: Dihydrotachysterol ; bioavailability ; pharmacokinetics ; human ; HPLC
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The bioavailability of four preparations containing dihydrotachysterol (DHT2) was tested in two separate trials with administration of single, oral doses of 1 mg per individual. The relative bioavailability of corresponding preparations (capsules vs capsules and oral solution vs oral solution) was tested in a randomised, crossover pattern within the same group of volunteers. Two different groups of 24 healthy volunteers took part in each trial. Solution and capsule bioavailability was also compared inter-individually. A new sensitive HPLC-method (quantification limit 0.5 ng · ml-1) was used for the measurement of DHT2 concentration in serum. Three of the preparations tested had a similar bioavailability (mean AUC values of 195.5–223 ng · h · ml-1); the bioavailability of the fourth preparation (A.T.10 oral solution) was considerably lower (mean AUC value 111.5 ng · h · ml-1). The present dosage recommendations of all four preparations are identical. A new dosage recommendation is thus required for the oral solution with low bioavailability (A.T.10).
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  • 48
    ISSN: 1432-1041
    Keywords: Doxycycline ; bioavailability ; pH dependent absorption ; pharmacokinetics ; carrageenate ; adverse events
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effect of increased gastric pH (obtained by pre-treatment with omeprazole) on the bioavailability of doxycycline monohydrate and doxycycline carrageenate has been investigated in 24 healthy volunteers, using an open, randomised, four-treatment, four-period, crossover, 2×2 factorial design. Each subject received a single dose of 100 mg of each of the doxycycline formulations with and without pre-treatment with omeprazole (40 mg daily for 7 days). The two formulations were bioequivalent (rate and extent) during fasting without omeprazole pre-treatment, whereas after omeprazole, the monohydrate showed a highly significant decrease in bioavailability (38% for AUC and 45% for Cmax) compared to the carrageenate formulation, which was not affected by prior administration of omeprazole. Many of the subjects did not reach a therapeutic plasma level of doxycycline during the combination of omeprazole and doxycycline monohydrate, and most adverse events (mainly gastrointestinal) were reported after this combination. As large populations of patients have a high gastric pH due to frequent use of H2-blockers, proton pump inhibitors and antacids, as well as to physiological achlorhydria, the decreased absorption of doxycycline monohydrate may well have a clinical impact, for example when the patients are treated with tetracyclines for an infection.
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  • 49
    ISSN: 1432-1041
    Keywords: Medifoxamine ; pharmacokinetics ; pharmacodynamics ; elderly volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetics and psychomotor effects of medifoxamine, a 5 HT reuptake inhibitory antidepressant, were studied in healthy elderly volunteers after single and multiple dosing. The elimination half life (t1/2z) after single doses of 300 mg was 2.8 h — almost identical to that found in young volunteers. After seven days of dosing at 100 mg three times daily the mean corrected AUC after 300 mg significantly increased from 1.04 to 1.34 mg.h.l−1 and t1/2z increased to 4.0 h (NS). There were no significant changes in critical flicker fusion frequency, symbol digit substitution, continuous attention or choice reaction times.
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  • 50
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    European journal of clinical pharmacology 46 (1994), S. 179-180 
    ISSN: 1432-1041
    Keywords: Teicoplanin ; haemodialysis ; renal failure ; pharmacokinetics
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  • 51
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    European journal of clinical pharmacology 46 (1994), S. 237-242 
    ISSN: 1432-1041
    Keywords: Metoprolol ; bioavailability ; bioequivalence ; receptor binding assay ; pharmacokinetics ; sustained release formulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The bioavailability and pharmacodynamic bioequivalence of a conventional and an experimental sustained-release formulation of 100 mg metoprolol tartrate were studied in a randomised cross-over study in seven healthy volunteers by assessing over 24 h the plasma kinetics of R,S-metoprolol, its β1-adrenoceptor binding component, and by determining the extent to which the active drug moiety in plasma occupied rabbit lung β1-and rat reticulocyte β2-adrenoceptors. The formulations differed markedly in their kinetic characteristics: the peak plasma concentration (Cmax) of R,S-metoprolol after administration of the conventional formulation was 140 ng·ml−1, (n=7) and it was approximately one-third of that after the sustained-release formulation, 49 ng·ml−1, (n=6); the AUC0–24 h-values for the formulations were 700 and 310 ng·h·ml−1, respectively. The Cmax for the β1-adrenoceptor binding component of metoprolol was 180 ng·ml−1 (n=7) after administration of the conventional, and 74 ng·ml−1 after administration of the sustained-release formulation. The corresponding AUC0–24 h-values for the receptor binding component were 920 and 470 ng·h·ml−1 (n=7). Thus, the kinetic differences between R,S-metoprolol and the β1-receptor binding component were considerable and they were affected by the type of formulation. In general, after administration of the sustained-release formulation, the percentage β1- and β2-adrenoceptor occupancy of metoprolol in plasma was 5–15% less than after administration of the conventional formulation. At 0.5–1.5 h after drug intake the average β1-adrenoceptor occupancy of the conventional formulation varied between 80–90% and that of the sustained release formulation between 20–76%. At these times the differences in receptor occupancy were significant; at 0.5–2 h after drug intake the average β2-adrenoceptor occupancy of the conventional formulation varied from 20–30%, and that of the sustained-release formulation was 2–17%. At other times the difference in receptor occupancy between the formulations was not significant. The results demonstrate that plasma concentration-kinetics were more discriminating than β-adrenoceptor-binding in analysing bioequivalence. It was possible to determine the bioavailability of the active ingredient of metoprolol and to study pharmacodynamic bioequivalence by using receptor binding assays.
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  • 52
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    European journal of clinical pharmacology 47 (1995), S. 507-511 
    ISSN: 1432-1041
    Keywords: Methotrexate ; Juvenile rheumatoid arthritis ; pharmacokinetics ; age dependence
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Children with juvenile rheumatoid arthritis (JRA) have been reported to require higher doses (per kg body weight) of methotrexate (MTX) than adults with rheumatoid arthritis to control their disease. The purpose of the present study was to characterise the plasma pharmacokinetics of MTX and its major metabolite, 7-hydroxymethotrexate (7-OHMTX) in children, and to compare the results with those previously obtained in adults. Thirteen patients (age 5–16 y) with JRA (median disease duration 5.5 y) were studied after once weekly oral administration of MTX (median 0.21 mg·kg−1). The analytical method was sufficiently sensitive to permit determination of plasma and urinary concentrations of MTX and 7-OHMTX during the entire dose interval in most of the patients. The dose normalized area under the plasma concentration versus time-curve (AUC) of MTX increased with the age of the children and was lower than previously found in adults. The dose normalized AUC of 7-OHMTX was not dependent on age. No correlation was found between the AUCs of MTX and 7-OHMTX. The results suggest that the age-dependence of the pharmacokinetics of MTX might explain the observation that at least some children require higher doses of MTX than adults to obtain a sufficient therapeutic effect.
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  • 53
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    European journal of clinical pharmacology 47 (1995), S. 525-530 
    ISSN: 1432-1041
    Keywords: Antipyrine disposition ; Obesity ; pharmacokinetics ; oxidative metabolism ; weight reduction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Following an overnight fast and 2 days of abstention from caffeine, a single 1.0-g oral dose of antipyrine was administered to 20 obese but otherwise healthy subjects (group A) and 11 healthy volunteers (group B). Weight, Body Mass Index (BMI) and % of Ideal Body Weight (IBW) were significantly greater in the obese than in the lean group. (Mean 110.4 vs 62.7 kg; 38.5 vs 22.3 kg · m−2 and 181vs 106 % respectively). In a subgroup of 6 obese subjects (group C) antipyrine was given again 11.3 months later after a 29.8 kg mean weight loss. Antipyrine apparent volume of distribution (V) and elimination half-life (t 1/2) were significantly greater in the obese than in the lean group (V 49.9 vs 34.3 l respectively; t 1/2 15.5 vs 12.0 h respectively), but its clearance rate (CLo) values were similar. V corrected for total body weight was significantly reduced in group A than in group B (0.45 vs 0.55 l · kg−1 respectively). Stratified comparison of antipyrine pharmacokinetics between obese and lean subjects according to age, gender and smoking habits did not alter the overall results. In group C, weight reduction was associated with a significant decrease in antipyrine V (from 51.8 to 47.5 l) and t 1/2 (from 15.1 to 12.7 h), and a non-significant increase in antipyrine CLo. We conclude that in severely obese subjects, antipyrine total V is mildly increased but V corrected for total body weight is significantly decreased. In addition, obesity is associated with a slight prolongation of antipyrine t 1/2 whereas its CLo is unaltered. These findings may indicate that obesity, even in its extreme form, has a negligible effect on the oxidative metabolic capacity of the liver.
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  • 54
    ISSN: 1432-1041
    Keywords: Piroxicam ; β-Cyclodextrin ; pharmacokinetics ; healthy volunteers ; multiple dose ; adverse event
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract CHF1194 is an inclusion complex of β-cyclodextrin with the nonsteroidal anti-inflammatory drug piroxicam. In man, β-cyclodextrin acts as a carrier of piroxicam. As the inclusion complex of piroxicam-β-cyclodextrin is wettable and more water soluble, the absorption rate of the drug is increased whilst its other pharmacokinetic characteristics remain unchanged. The aim of the present study in 12 healthy subjects was to compare the oral bioavailability of 20 mg piroxicam in a CHF1194 tablet and a plain piroxicam capsule after a single dose and after two weeks of once daily administration, and also to assess the plasma levels and urinary excretion of β-cyclodextrin after CHF1194 administration. The two treatments were administered in cross-over fashion, separated by a wash-out period of three weeks. Piroxicam, 5′-hydroxypiroxicam and β-cyclodextrin were monitored in plasma and urine for 120 h after the first and last doses. Clinical tolerance was excellent and no adverse event occurred during either phase of the study. The extent of absorption of piroxicam from the CHF1194 tablet after the single dose was equivalent to that after the plain piroxicam capsule, within confidence limits of less than 80–125%. After repeated dosing, CHF1194 yielded the same steady-state systemic concentrations of piroxicam and 5′-hydroxypiroxicam as the reference capsule, and similar excretion pattern of the metabolite. After both single and multiple dosing, piroxicam was absorbed more rapidly after CHF1194, an expected consequence of the complexation of piroxicam with β-cyclodextrin. This may be of therapeutic interest as it might accelerate the onset of pain relief. The pharmacokinetics of piroxicam was linear after the doses used here, suggesting that long term treatment with CHF1194 should not require any change in dosing regimen. Even after 14 days of repeated administration of CHF1194, β-cyclodextrin could not be detected in plasma or urine, suggesting that in man the unchanged oligosaccharide was absorbed to a very small extent.
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  • 55
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    European journal of clinical pharmacology 46 (1994), S. 575-575 
    ISSN: 1432-1041
    Keywords: Renal clearance ; pharmacokinetics
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  • 56
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    European journal of clinical pharmacology 47 (1994), S. 75-79 
    ISSN: 1432-1041
    Keywords: Diltiazem ; Angina pectoris ; controlled release formulation ; metoprolol ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Diltiazem CR tablets 120 mg b.i.d. for 1 week were compared with plain tablets 60 mg q.i.d. in 13 healthy male volunteers in a study of pharmcokinetic variables. Their antianginal efficacy was also compared in 23 patients with stable angina pectoris who were already on metoprolol. Both studies were of randomised, cross over design, and the clinical study was double blind. The pharmacokinetic variables of the two formulations were very similar except for the longer tmax of 4.4 h for diltiazem CR in comparison to 2.9 h for the plain tablets. The mean relative bioavailability of diltiazem CR in comparison with plain tablets was 1.14. The clinical study showed that after four weeks on diltiazem CR 120 mg b.i.d. or diltiazem plain tablets 60 mg q.i.d. in addition to metoprolol, there were significant decreases in weekly anginal attacks from 11 to 5 attacks/week, the number of nitroglycerin tablets consumed from 6 to 3 tablets/week, and an increase in the maximum workload from 116 to 126 and 123 W for diltiazem CR and plain diltiazem tablets, respectively, as compared to placebo. Five of the patients were angina free during diltiazem treatment. No difference in antianginal efficacy between the two preparations was seen. It was concluded that CR 120 mg b.i.d. appears bioequivalent to plain diltiazem tablets 60 mg q.i.d.
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  • 57
    ISSN: 1432-1041
    Keywords: Oxcarbazepine ; 10,11-dihydro-10-hydroxy-carbamazepine ; renal impairment ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract We have studied the effect of renal impairment on the pharmacokinetics of oxcarbazepine, its active monohydroxy-metabolite (which predominates in plasma), their glucuronides, and the inactive dihydroxy-metabolite after a single oral dose of oxcarbazepine (300 mg). Six subjects with normal renal function and 20 patients with various degrees of renal impairment participated. The mean areas under the plasma concentration-time curves of oxcarbazepine and its monohydroxy-metabolite were 2–2.5-times higher in patients with severe renal impairment (CLCR〈10 ml·min−1) than in healthy subjects. The apparent elimination half-life of the monohydroxy-metabolite [19 (SD 3) h] in these patients was about twice that in healthy subjects. The effect of renal impairment on the plasma concentrations of glucuronides was more marked. The renal clearances of the unconjugated monohydroxy-metabolite and its glucuronides (the main compounds recovered in urine) correlated well with creatinine clearance. The maximum target dose in patients with slight renal impairment (CLCR〉30 ml·min−1) should not be changed. In patients with moderate renal impairment (CLCR10–30 ml·min−1) it should be reduced by 50%. In patients with severe renal impairment (CLCR〈10 ml·min−1), the glucuronides of oxcarbazepine and its monohydroxy-metabolite are likely to accumulate during repeated administration, and dosage adjustment of oxcarbazepine in these patients could not be proposed from this single administration study.
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  • 58
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    European journal of clinical pharmacology 48 (1995), S. 385-390 
    ISSN: 1432-1041
    Keywords: Furosemide ; Dialysis ; continuous ambulatory peritoneal ; drug disposition ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Single doses of oral and intravenous furosemide were given to 8 healthy male volunteers (40 mg) and 11 patients with renal failure maintained on continuous ambulatory peritoneal dialysis (CAPD) (80 mg). In the volunteers, absorption was variable. Only one half of the intravenous dose and one third of the oral dose was available for renal pharmacological action as judged by the urinary recovery. In the patients, absorption was also variable and was markedly delayed (t max 128 vs 90 min) but more complete (bioavailability 70.1 vs 53.6%). The differences between the two groups were not significant, however (95% C.I.: -90 to 30 and -40.4 to 7.5 respectively). The mean elimination half-life was significantly longer in the patients following both the oral (228 vs 65.1 min) and intravenous dose (195 vs 60.3 min). The total body clearance of furosemide in the volunteers was 138 ml·min−1 and this was much lower in the CAPD patients (61.9 ml·min−1) in whom the renal clearance was minimal. The peritoneal clearance of furosemide was negligible. Although there were trends indicating differences in absorption between the two groups, the significant differences in furosemide disposition observed in CAPD patients were due to renal failure.
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  • 59
    ISSN: 1432-1041
    Keywords: Caffeine ; Cardio-green ; Indocyanine Green ; altitude ; metabolism ; pharmacokinetics ; hypoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The effects of chronic exposure to high altitude on the pharmacokinetics of caffeine and cardiogreen (ICG) were examined in eight healthy males (23–35 y) at sea level (SEA) and following 16 days residence at 4300 m (ALT). ICG (0.5 mg · kg−1) was administered as an intravenous bolus and caffeine (4 mg · kg−1) in an orally ingested solution. The concentration of ICG, caffeine, and the primary metabolites of caffeine (MET) were determined in serial blood samples and their pharmacokinetics computed. In comparison to SEA, ALT resulted in a significant decrease in the caffeine half-life (t1/2, 4.7 vs 6.7 h) and area under the curve (2.5 vs 3.7 g · 1−1 · min−1), and increased clearance (117 vs 86 ml · min−1 · 70 kg−1). In ALT the area under the curve of ICG significantly decreased (85 vs 207 mg · 1−1 · min−1) and the volume of distribution and clearance increased (5.2 vs 2.41 and 532 vs 234 ml · min−1 respectively) compared to SEA. There was a significant increase in the AUC ratio of MET to caffeine indicating that either metabolite formation or elimination was increased in ALT. These results demonstrate that in humans, chronic exposure to 4300 m results in the modification of the pharmacokinetics of caffeine and ICG.
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  • 60
    ISSN: 1432-1041
    Keywords: Diltiazem ; sustained-release formulation ; pharmacokinetics ; bioavailability ; bioequivalence
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The usual dosage regimen of diltiazem (Tildiem) is 60 mg 3–4 times a day. A sustained-release formulation has been developed (Mono-Tildiem LP 300 mg) in order to allow a single daily administration. Two repeated dosing studies were performed in healthy volunteers. The absolute bioavailability of sustained-release diltiazem LP 300 mg was investigated using concomitant i.v. administration of 13C-labelled drug: absolute bioavailability of the “once a day” formulation was 35%. The second study compared sustained-release diltiazem LP 300 mg with the standard formulation of diltiazem. The results showed that the diltiazem plasma concentrations obtained after the LP formulation remained stable between 2 and 14 h after administration and were compatible with a once a day administration. Relative bioavailability of sustained-release diltiazem LP 300 mg was 79.3% compared with diltiazem. Therefore, a unitary dose of sustained-release diltiazem LP 300 mg was chosen as the dose equivalent to the daily dose administered with the standard diltiazem formulation.
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  • 61
    ISSN: 1432-1041
    Keywords: Diabetes ; Human insulin ; Lorazepam ; pharmacokinetics ; glucuronidation ; enterohepatic circulation ; animal insulin
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetics of lorazepam was examined in 10 male patients with insulin-dependent diabetes mellitus before and following treatment with neomycin and cholestyramine. Neomycin and cholestyramine were given in an attempt to block the enterohepatic circulation of lorazepam and so to permit an in vivo estimate of hepatic glucuronidation. The volume of distribution and clearance of free lorazepam in diabetic patients were not significantly different from the corresponding estimates in 14 normal controls. Neomycin and cholestyramine increased the clearance of lorazepam by 63% consistent with their effect in non-diabetic controls. However, patients on beef/pork insulin exhibited a greater than normal increase on this interupting regimen (125%), and had a significantly greater neomycin/cholestyramine cycling-interrupted clearance of lorazepam than either normal controls or patients on human insulin (15.4 vs. 6.96 and 7.87 ml·min−1·kg−1). The clearance was correlated positively and significantly with HbA1c and glycated proteins (fructosamine), but only in patients on human insulin. Thus, the pharmacokinetics of lorazepam was not altered in patients with insulin-dependent diabetes mellitus. However, it is possible that there are differences in the rate and extent of hepatic glucuronidation and enterohepatic circulation of lorazepam between patients treated with beef/pork and human insulins and between diabetics treated with beef/pork insulin and non-diabetic controls.
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  • 62
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    European journal of clinical pharmacology 48 (1995), S. 273-277 
    ISSN: 1432-1041
    Keywords: Mesalamine ; 5-aminosalicylic acid ; controlled release capsules ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract One gram single dose of Pentasa controlled-release capsules was administered to 24 healthy volunteers under fasting condition. Mean plasma 5-aminosalicylic acid (5-ASA) and acetyl 5-ASA concentrations peaked at 0.53 μg · ml−1 and 1.33 μg · ml−1 from 3 to 4 hours following dosing, respectively. The half-lives of both compounds could not be determined as absorption of 5-ASA was continuous throughout the gastrointestinal tract. An average of 29.4% (CV: 27%) of the dose was excreted in the urine primarily as acetyl 5-ASA. Up to 91.1% of the dose was released from the capsules. Forty percent of the dose (CV: 40%) was eliminated in the feces, with 8.9% of the dose remained as formulation bounded 5-ASA, indicating that controlled-release capsules continue to release drug throughout the GI tract. 5-ASA contributed 46.7% of the salicylates eliminated in the feces and acetyl 5-ASA accounted for the balance. Controlled-release capsules produced three times more total salicylates and 10 times more total and free 5-ASA in the feces than did 5-ASA suspension. Thus, while lower systemic levels of salicylates were absorbed, greater therapeutic quantities of 5-ASA were available in the bowel.
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  • 63
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    European journal of clinical pharmacology 49 (1995), S. 127-137 
    ISSN: 1432-1041
    Keywords: Thiopental ; Pharmacokinetic modelling ; pharmacokinetics ; single dose ; multiple dosing ; neurosurgical patients ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Thiopental was administered to neurosurgical patients for cerebral protection and its pharmacokinetic parameters were determined after a single bolus of 540, 1000 or 1500 mg (3 subjects) or after multiple doses of 250 mg (5 subjects) and 500 mg (2 subjects) every two hours for up to 7 days. The data were analysed by a two- or three- compartment model and linear kinetics. After a single IV bolus, the mean initial volume of distribution (V1) was 0.4811·kg−1, and the steady-state volume of distribution (Vss) was 2.16 1·kg−1. The distribution (t1/2α) and elimination (t1/2β) half-lives were 0.590 and 5.89 h, respectively, and the mean residence time (MRT) was 7.44 h. The clearance was 5.41 ml·min−1·kg−1. With repeated injections, the pharmacokinetic parameters for each patient were estimated taking into account all administered doses and blood samples, which were taken whenever possible daily at steady state and after the last dose. The variability observed in the pharmacokinetic parameters of thiopental reflected by the coefficient of variation (CV%) was wide but was of similar magnitude within patients (CVintra) as it was between patients (CVinter). The steady-state trough plasma concentration (Cmin obs) ranged from 4.8 to 30 mg·1−1 (mean 16.0 mg·1−1 and median 14.3 mg·1−1). Peak concentrations (Cmax obs) ranged from 8.35 to 45 mg·1−1 (25.4 mg·1−1, and median 23.3 mg·1−1). The values of V1 and Vss were similar to those obtained after a single dose. For V1, the mean was 0.333 1·kg−1. The mean Vss was 2.68 1·kg−1, with a CVintra of 12.6 to 56% and a CVinter of 13.2%. A shorter distribution half-life t1/2α was noted on multiple dosing; the mean value was 0.122 h. The elimination half-life t1/2β and the mean residence time became longer due to a decrease in clearance. For t1/2β the mean value was 16.3 h. The mean MRT was 21.9 h, CVintra 9.19 to 48.5%, and the CVinter 35.3%. The mean clearance was 2.16 ml·min−1·kg−1, CVintra 7.28 to 25.5%, and the CVinter 20.4%. This value is 50% lower than after a single dose. Identification of the kinetic parameters of thiopental allows simulation of the effects of doses on subsequent plasma levels and will permit a priori prediction of day to day adjustment of drug dosage.
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  • 64
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    European journal of clinical pharmacology 49 (1995), S. 139-143 
    ISSN: 1432-1041
    Keywords: Intestinal absorption ; Amoxicillin ; pharmacokinetics ; maximum entropy ; input rate
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract A computer program applying the principle of maximum entropy to the analysis of drug absorption rate has been developed. Plasma concentrations of amoxicillin obtained after oral and intravenous dosing have been analysed, together with simulated data corresponding to a complex input. Amoxicillin absorption rates devised by the program were similar to those obtained by a standard deconvolution method, although they were displayed as an almost continuous profile. However, improbable fluctuations were obtained with some data sets and the fraction absorbed was underestimated by 13%. With the simulated data, the maximum entropy program did not provide a better solution than the standard deconvolution procedure, and it was sensitive to the addition of random error and to the number of samples. The maximum entropy principle, as implemented in our computer program, may not have a better performance than standard deconvolution procedures, especially in human experiments where the number of blood samples is usually limited.
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  • 65
    ISSN: 1432-1041
    Keywords: Antiallergic drug ; FK613 ; pharmacokinetics ; histamine skin-test ; drug formulation ; urinary excretion ; safety
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract The pharmacokinetic and pharmacodynamic properties of FK613, a novel indolyl piperidine derivative, were investigated after oral administrations of 5, 10 and 20 mg in hard gelatin capsules to healthy male volunteers. FK613 was rapidly and almost completely absorbed, and 〉89% was recovered in the urine as the unchanged form. The urinary excretion of FK613 was linearly correlated with plasma concentration and its low water solubility was the main concern regarding the safety. In another experiment using a double-blind crossover design, in which 0 (placebo), 5 and 20 mg FK613 were administered to determine the plasma concentration-effect relationship, suppression of the intradermal histamine-induced skin reaction by FK613 was observed. Thus, the maintenance of a plasma concentration of FK613 in the range of 80–250 ng · ml-1 was recommended to ensure the suppression of histamine-induced wheal by 〉50% and not to exceed the solubility in urine. To achieve this, a new hydrogel-type formulation of FK613 was developed, with the aim both of delaying its absorption, so as to suppress the sharp rise in plasma concentration, and of maintaining the effective concentration for a longer period of time. This formulation was administered after meals at the doses of 20, 30, 40, 50 and 60 mg, and at repeated doses of 40 mg twice daily for 6.5 days to evaluate the pharmacokinetics and safety in healthy subjects. The area under the plasma concentration curve increased linearly with dose, whereas maximum plasma concentration (Cmax) tended to peak as dose increased, indicating the desirable properties of this formulation. Although Cmax exceeded 250 ng/ml at doses of 30 mg or more, no urinary crystal formation was observed on careful inspection of urine.
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  • 66
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    European journal of clinical pharmacology 52 (1997), S. 235-237 
    ISSN: 1432-1041
    Keywords: Key words Itraconazole ; Coca Cola; acidic beverage ; absorption ; pharmacokinetics ; drug concentration ; food
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To evaluate the effectiveness of Coca-Cola in enhancing the absorption of itraconazole. Methods: Eight healthy volunteers were randomized to receive two treatment sequences in a two-way crossover design with a 1-week wash-out period separating each study treatment. Treatment I, the control, consisted of 100 mg itraconazole with 325 ml water. Treatment II was identical to treatment I, except that itraconazole was administered with 325 ml of Coca-Cola (pH 2.5). Results: Serum itraconazole concentrations, after administration with Coca-Cola (treatment II), were higher than after administration with water (treatment I). The mean AUC was 1.12 vs 2.02 μg · h · ml−1, the mean Cmax was 0.14 vs 0.31 μg · ml −1and the mean tmax was 2.56 vs 3.38 h in treatments I and II, respectively. Conclusion: The absorption of itraconazole can be enhanced by Coca-Cola.
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  • 67
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    European journal of clinical pharmacology 52 (1997), S. 289-292 
    ISSN: 1432-1041
    Keywords: Key words Nicardipine; enantiomers ; healthy volunteers ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: The present study was conducted to compare pharmacokinetic behaviors of nicardipine enantiomers given in different doses with different formulations of racemic nicardipine in healthy volunteers. Methods: One or two 20-mg racemic nicardipine tablets, and a 40-mg sustained-release capsule of nicardipine were administered to eight healthy volunteers in a cross-over fashion and pharmacokinetic parameters were evaluated. Enantiomer concentrations were determined by GC-MS combined with chiral stationary phase HPLC. Results and conclusions: Serum concentration of (+)-nicardipine was approximately 2–3 times higher than that of (−)-nicardipine in 20- and 40-mg doses of conventional formulations and a non-linear increase in bioavailability with dose was demonstrated. The value for AUC of (+)-nicardipine was approximately 2.3–2.8 times greater than that of the (−)-nicardipine (P 〈 0.05) when 20 and 40 mg racemic nicardipine were administered in a conventional preparation. Relative bioavailability of the sustained-release preparation vs the conventional preparation was 28% and 44% for (+)- and (−)-nicardipine, respectively, for the 40-mg dose.
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  • 68
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    European journal of clinical pharmacology 52 (1997), S. 379-381 
    ISSN: 1432-1041
    Keywords: Key words Nitroglycerin; transdermal nitrate ; pharmacokinetics ; patch renewal ; exercise test
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: We examined whether nitroglycerin (glyceryl trinitrate, GTN) patch treatment for 24 h could induce local cutaneous changes that impaired drug delivery and clinical efficacy. Methods: Twenty angina patients were exercise-tested after 2 and 24 h of treatment and then 2 h after patch renewal. The patch was either renewed on a new skin location or on the previous application site in a randomised, double-blind, cross-over protocol. GTN plasma concentrations and finger plethysmography were obtained before and after each exercise test. Results and conclusions: The clinical efficacy, the effect seen on plethysmography and the GTN plasma concentrations tended to increase after patch renewal, regardless of the application site of the renewed patch. Hence, cutaneous changes of clinical importance could not be demonstrated.
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  • 69
    ISSN: 1432-1041
    Keywords: Key words Angiotensin II ; Valsartan; AT1 receptor antagonist ; healthy volunteers ; pharmacokinetics ; renin-angiotensin system ; blood pressure ; passive tilting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Pharmacokinetics, pharmacodynamic effects and tolerability of 200 mg valsartan, once-daily for 8 days, were investigated in 16 healthy, normotensive volunteers on a normal sodium diet. Methods: This was a double-blind, placebo-controlled, randomized crossover study. Drug concentrations in plasma and urine, angiotensin II (Ang II) concentrations in plasma, systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR) in the supine position and 3 min after passive head-up tilting, as well as safety parameters (ECG, clinical chemistry and hematology, renal water and electrolyte excretion) were measured over 24 h after the first dose (day 1) and at steady state on day 8. Results: Absorption and distribution of valsartan were rapid (Cmax, 2 h; t½λ1 〈 1 h), followed by a slower terminal elimination phase (t½λ2, 6 h) on days 1 and 8, with little accumulation in plasma (increase of 20% on day 8). Less than 10% of the dose was excreted unchanged in urine. The increase in plasma Ang II (Cmax, 6 h) was significantly enhanced at steady state. Supine SBP and DBP significantly decreased on day 8 only, by an average of −3.6 and −2.4 mmHg, respectively, versus placebo, without a concomitant increase in HR. Upon passive tilting, the increase in DBP, normally reinforced by sympathetic renin release, was slightly but significantly blunted on day 1 (−2.0 mmHg) and day 8 (−4.0 mmHg) of treatment with valsartan versus placebo. The orthostatic reflex increase in HR was slightly enhanced compared with placebo by an average of 2.8 beats · min−1 on day 1 and by 2.9 beats · min−1 on day 8. Valsartan was well tolerated and had no influence on ECG, clinical laboratory parameters, and water, electrolyte and uric acid excretion. Conclusions: Pharmacokinetics of valsartan are unchanged after multiple once-daily dosing, with little (expected) accumulation in plasma. Effects of 200 mg valsartan on blood pressure in healthy subjects on a normal sodium intake are small and become more prominent after repeated dosing. Indirect evidence of AT1 blockade by valsartan is demonstrated by an increase of plasma Ang II and by a blunted DBP response to passive tilting. The decrease in blood pressure at steady state enhances the increase in plasma Ang II. Valsartan is well tolerated and is devoid of effects on water, electrolyte and uric acid excretion at 200 mg per day in healthy normotensive volunteers.
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  • 70
    ISSN: 1432-1041
    Keywords: Key words Tiludronate; healthy volunteers ; bisphosphonates ; pharmacokinetics ; calcium metabolism ; bone resorption ; adverse events
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: A double-blind, placebo-controlled study was conducted to assess the pharmacokinetics and pharmacodynamics of the bisphosphonate tiludronic acid, administered once daily as sodium tiludronate 200, 400, 600 and 800 mg for 12 days. Four groups of ten subjects participated in the study, with a drug to placebo ratio of 4:1. Methods: Pre-dose blood samples were taken on alternate days, starting on Day 1 and additional samples were collected over 144 h following the final dose on Day 12. Urine was collected over 24 h after the final dose. Indices of calcium homeostasis and biochemical markers of bone turnover were assessed during the study as pharmacodynamic parameters. Tolerability was evaluated with special emphasis on renal function and gastrointestinal irritation. Adverse experiences were assessed at regular time intervals. Results and conclusions: Steady state was attained from Day 4 (200 mg) or from Day 6 (400, 600 and 800 mg). Following the final dose on Day 12, minimal plasma concentrations (Cmin) ranged between 0.19 and 1.5 mg ⋅ l−1, and maximal plasma concentrations (Cmax) between 1.1 and 7.8 mg⋅l−1 for the lowest and highest doses, respectively. A supra-proportional increase in Cmax, AUC24 and Ae 24 with dose was observed. There was a linear relationship between the plasma tiludronic acid and its urinary excretion rate, so, the disproportional rise in Cmax and AUC24 with increasing dose could not be attributed to saturation of renal excretion. Certain indices of calcium homeostasis changed significantly during the study, but generally, became only prominent at the highest dose level of 800 mg. Total serum calcium and the urinary calcium/creatinine clearance ratio fell, indicating depression of osteoclastic bone resorption, which was not revealed by serum osteocalcin levels probably because of the brevity of the treatment (12 days). In response to the decline in serum calcium, serum 1,25-dihydroxyvitamin D3 and intact PTH (1–84) levels increased. None of the safety parameters raised any concerns about the safety of sodium tiludronate administered in this way.
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  • 71
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    European journal of clinical pharmacology 51 (1996), S. 189-193 
    ISSN: 1432-1041
    Keywords: Key words Dihydropyridine ; Amlodipine ; Grapefruit juice; flavonoids ; interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract. Objective: This study was performed to assess whether coadminstration with grapefruit juice significantly affects the pharmacokinetics of amlodipine, a dihydropyridine class calcium antagonist with slow absorption, distribution and low plasma clearance. The primary objective was to evaluate whether short exposure to grapefruit juice could affect the metabolism of amlodipine to an extent similar to that previously demonstrated for other dihydropyridines (e.g. felodipine, nisoldipine, nitrendipine). Methods: Twelve healthy male volunteers followed a randomised, open crossover study design, comparing the effect of a single oral dose of amlodipine (5 mg) taken together with a glass of grapefruit juice (250 ml) vs water. Blood samples to determine plasma concentration were taken and blood pressure (BP) and heart rate (HR) were measured throughout the study. Results: When amlodipine was coadministered with grapefruit juice, Cmax was 115% and AUC(0–72 h) was 116% compared with water, but tmax was not significantly changed. There were no significant differences in BP and HR between the two treatments. A small decrease in diastolic BP, however, was observed in both treatments 4–8 h after drug administration, coinciding with Cmax, but this was normalised after 12 h. The BP reduction seen was compensated by a slight increase in HR, which remained throughout the study. Conclusion: An interaction between grapefruit juice and amlodipine was demonstrated. The haemodynamic data showed that a dose of 5 mg was sufficient to achieve a BP reduction in healthy subjects, but the increase in amlodipine plasma concentration seen after intake of grapefruit juice was too small to significantly affect BP or HR. The clinical significance of this food/drug interaction, however, cannot be ignored since there is considerable variation between individuals and a more extensive intake of grapefruit juice might give more pronounced effects.
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  • 72
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    European journal of clinical pharmacology 51 (1996), S. 259-264 
    ISSN: 1432-1041
    Keywords: Key words Nebivolol ; Hypertension; d ; l-enantiomers ; pharmacokinetics ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Nebivolol is a selective β1-adrenergic receptor blocker possessing an ancillary vasodilating effect. The objective of the present study was to study the haemodynamic and pharmacokinetic properties of nebivolol 5 mg once daily in a double-blind, placebo-controlled cross-over study. Methods: Fifteen patients, 12 men and 3 women, with essential hypertension were investigated. Blood pressure and peripheral circulation were determined after acute oral nebivolol administration, 5 mg daily, and after 4 weeks treatment. Results: The acute effect on blood pressure upon single-dosing was weak and non-significant. After 4 weeks both systolic blood pressure (152 vs 163 mmHg) and diastolic blood pressure (89 vs 97 mmHg) were significantly reduced after nebivolol treatment as compared to placebo. Following the first dose the venous volume was higher on placebo (5.88 ml ⋅ 100 ml−1 tissue) as compared to active nebivolol treatment (5.17 ml ⋅ 100 ml−1 tissue), while there were no statistically significant differences with regard to venous plethysmographic findings after 1 month on placebo (5.53 ml ⋅ 100 ml−1 tissue) or on active treatment (5.97 ml ⋅ 100 ml−1 tissue). Calculated peripheral resistance did not differ between active treatment (617 units) or placebo (548 units) after the first dose, whereas it was significantly lowered after 4 weeks of nebivolol treatment (483 units) as compared to placebo (593 units). Conclusions: Oral nebivolol 5 mg once daily lowered blood pressure and heart rate during steady state compared to placebo. Moreover, venous volume was reduced during acute but not steady-state dosing, while peripheral resistance was unaffected in the acute phase but reduced during steady state. Plasma concentrations of the separate enantiomers plus hydroxylated metabolites after the first and last dose in hypertensive patients were similar to those in healthy subjects.
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  • 73
    ISSN: 1432-1041
    Keywords: Key words Pantoprazole; Proton pump inhibitor drug interaction ; oral anticoagulant phenprocoumon ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Pantoprazole is a selective proton pump inhibitor characterized by a low potential to interact with the cytochrome P450 enzymes in man. Due to the clinical importance of an interaction with anticoagulants, this study was carried out to investigate the possible influence of pantoprazole on the pharmacodynamics and pharmacokinetics of phenprocoumon. Methods: Sixteen healthy male subjects were given individually adjusted doses of phenprocoumon to reduce prothrombin time ratio (Quick method) to about 30–40% of normal within the first 5–9 days and to maintain this level. The individual maintenance doses remained unaltered from day 9 on and were administered until day 15. Additionally, on study days 11–15, pantoprazole 40 mg was given per once daily. As a pharmacodynamic parameter, the prothrombin time ratio was determined on days 9 and 10 (reference value) and on days 14 and 15 (test value), and the ratio test/reference was evaluated according to equivalence criteria. Results: The equivalence ratio (test/reference) for prothrombin time ratio was 1.02 (90% confidence interval 0.95–1.09), thus fulfilling predetermined bioequivalence criteria (0.70–1.43). The pharmacokinetic characteristics AUC0–24h and Cmax of S(−)-and R(+)-phenprocoumon were also investigated using equivalence criteria. Equivalence ratios and confidence limits of AUC0–24h and of Cmax of S(−)-phenprocoumon (0.93, 0.87–1.00 for AUC0–24h; 0.95, 0.88–1.03 for Cmax) and of R(+)-phenprocoumon (0.89, 0.82–0.96; 0.9, 0.83–0.98) were within the accepted range of 0.8–1.25. Conclusion: Pantoprazole does not interact with the anticoagulant phenprocoumon on a pharmacodynamic or pharmacokinetic level. Concomitant treatment was well tolerated.
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  • 74
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    European journal of clinical pharmacology 51 (1997), S. 359-366 
    ISSN: 1432-1041
    Keywords: Key words Sufentanil ; pharmacokinetics ; haemo dynamics ; different infusion rates ; coronary surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract    Objective: Pharmacokinetics and haemodynamic effects of a total dose of 15 μg · kg−1 sufentanil, an opioid anaesthetic agent, were studied in patients undergoing aortocoronary bypass surgery at three infusion rates of 30 (group I), 5 (group II), and 2 (group III) μg · kg−1 · min−1, respectively. Results: Plasma concentrations of sufentanil could be optimally characterized by a linear biexponential pharmacokinetic model. Non-compartmental analyses indicated that there was no significant difference in the values of clearance (11.6, 13.3, 14.3 ml · min−1 · kg−1), steady-state volume of distribution (0.220, 0.255 and 0.331 l · kg−1) and mean residence time (18.8, 13.3 and 14.3 min) among the groups. The observed mean Cmax values of 421 (group I), 125 (group II), and 53 (group III) ng · ml−1 and observed mean AUC values from 0 to 3 min were all consistent with the dosing regimens. There were large inter-individual variations in haemodynamic response. Compared to plasma data, a delay in haemodynamic effects was found. Times to reach peak haemodynamic effect ranged from 4.3 to 4.9 min for group I, from 4.6 to 6.1 min for group II, and from 9.9 to 11.3 for group III. Except heart rate, peak haemodynamic effects in these study patients generally ranged from 20.9% to 35.2%. Significant reductions in the area under the effect-time profiles of mean arterial blood pressure and systemic vascular resistance were observed in group II and group III, but not in group I. Significant reductions in the area under the effect-time profiles of left ventricular stroke work index were observed in group III only. No effect on heart rate was found in any group. Conclusion: Our findings suggested that a slower infusion rate of sufentanil at a dose of 15 μg · kg−1 tends to give a greater reduction in mean arterial blood pressure, systemic vascular resistance, and left ventricular stroke work index than does a faster infusion rate.
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  • 75
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    European journal of clinical pharmacology 51 (1997), S. 415-419 
    ISSN: 1432-1041
    Keywords: Key words Midazolam ; Fluconazole ; CYP3A4 ; interaction ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Midazolam is a short-acting benzodiazepine hypnotic extensively metabolized by CYP3A4 enzyme. Orally ingested azole antimycotics, including fluconazole, interfere with the metabolism of oral midazolam during its absorption and elimination phases. We compared the effect of oral and intravenous fluconazole on the pharmacokinetics and pharmacodynamics of orally ingested midazolam. Methods: A double-dummy, randomized, cross-over study in three phases was performed in 9 healthy volunteers. The subjects were given orally fluconazole 400 mg and intravenously saline within 60 min; orally placebo and intravenously fluconazole 400 mg; and orally placebo and intravenously saline. An oral dose of 7.5 mg midazolam was ingested 60 min after oral intake of fluconazole/placebo, i.e. at the end of the corresponding infusion. Plasma concentrations of midazolam, α-hydroxymidazolam and fluconazole were determined and pharmacodynamic effects were measured up to 17 h. Results: Both oral and intravenous fluconazole significantly increased the area under the midazolam plasma concentration-time curve (AUC0–3, AUC0–17) 2- to 3-fold, the elimination half-life of midazolam 2.5-fold and its peak concentration (Cmax) 2- to 2.5-fold compared with placebo. The AUC0–3 and the Cmax of midazolam were significantly higher after oral than after intravenous administration of fluconazole. Both oral and intravenous fluconazole increased the pharmacodynamic effects of midazolam but no differences were detected between the fluconazole phases. Conclusion: We conclude that the metabolism of orally␣administered midazolam was more strongly inhibited by oral than by intravenous administration of fluconazole.
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  • 76
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    European journal of clinical pharmacology 51 (1997), S. 421-425 
    ISSN: 1432-1041
    Keywords: Key words Warfarin ; Meloxicam ; interaction ; pharmacokinetics ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: The effect of multiple oral doses of meloxicam 15 mg on the pharmacodynamics and pharmacokinetics of warfarin was investigated in healthy male volunteers. Warfarin was administered in an individualized dose to achieve a stable reduction in prothrombin times calculated as International Normalized Ratio (INR) values. Then INR- and a drug concentration-time profile was determined. For the interaction phase, meloxicam was added for 7 days and then INR measurements and the warfarin drug profiles were repeated for comparison. Overall, warfarin treatment lasted for 30 days. Results: Warfarin and meloxicam were well tolerated by healthy volunteers in this study. Thirteen healthy volunteers with stable INR values entered the interaction phase. Prothrombin times, expressed as mean INR values, were not significantly altered by concomitant meloxicam treatment, being 1.20 for warfarin alone and 1.27 for warfarin with meloxicam cotreatment. R- and S-warfarin pharmacokinetics were similar for both treatments. Geometric mean (% gCV) AUCSS values for the more potent S-enantiomer were 5.07 mg · h · l−1 (27.5%) for warfarin alone and 5.64 mg · h · l−1 (28.1%) during the interaction phase. Respective AUCSS values for R-warfarin were 7.31 mg · h · l−1 (43.8%) and 7.58 mg · h · l−1 (39.1%). Conclusion: The concomitant administration of the new non-steroidal anti-inflammatory drug (NSAID) meloxicam affected neither the pharmacodynamics nor the pharmacokinetics of a titrated warfarin dose. A combination of both drugs should nevertheless be avoided and, if necessary, INR monitoring is considered mandatory.
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  • 77
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    European journal of clinical pharmacology 52 (1997), S. 391-396 
    ISSN: 1432-1041
    Keywords: Key words Lansoprazole ; CYP2C19; genotype ; hydroxy lation ; polymorphism ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: We investigated whether interindividual differences in the pharmacokinetic disposition of lansoprazole are attributed to the genetic polymorphism of CYP2C19 which occurred by two mutations, CYP2C19m1 and CYP2C19m2, in 20 Japanese subjects. Methods: Polymerase chain reaction (PCR) restriction fragment length polymorphism procedures were used to detect the CYP2C19m1 mutation in exon 5 and the CYP2C19m2 mutation in exon 4 using SmaI and BamHI, respectively. Results: Ten subjects were homozygous (wt/wt subjects) for the wt allele in both exon 5 and exon 4, four subjects were heterozygous (wt/m1) for the CYP2C19m1 mutation, and two subjects were heterozygous (wt/m2) for the CYP2C19m2. The remaining four subjects had both mutated alleles in CYP2C19 genes, i.e., two were homozygous (m1/m1) for the defect in exon 5 and two were heterozygous (m1/m2) for the two defects in exons 5 and 4. The subjects in group 1 (wt/wt, wt/m1 and wt/m2) were the extensive metabolizers (EMs) for 5-hydroxylation of lansoprazole and were in the range of hydroxylation indexes from 3.83 to 19.8, whereas the subjects in group 2 (m1/m1 and m1/m2) were the poor metabolizers (PMs) and the indexes were in the range of 38.5 to 47.6. In group 2, AUC, t1/2 and CL/f of lansoprazole were significantly greater, longer, and lower, respectively, than those in group 1. Conclusion: The hydroxylation of lansoprazole to 5-hydroxylansoprazole was apparently impaired in the subjects with the genetic defects of CYP2C19 (m1/m1 or m1/m2).
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  • 78
    ISSN: 1432-1041
    Keywords: Halofantrine ; Malaria falciparum ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Halofantrine is a new blood schizontocidal drug used for the treatment of multidrug-resistant falciparum malaria. The pharmacokinetics of halofantrine (HAL) and its principal metabolite, N-desbutylhalofantrine (BHAL), was investigated in 6 adult male patients of Melanesian origin with uncomplicated falciparum malaria. The patients received 500 mg of halofantrine hydrochloride at times 0, 6 and 12 h (total 1.5 g). All patients responded to treatment with a mean parasite clearance time of 52.7 h and a mean fever clearance time of 33.8 h. The following kinetic parameters (mean values) were determined for HAL and BHAL, respectively: maximum plasma concentration (Cmax)=896 and 491 ng·ml−1; time to reach the Cmax (tmax)=15 and 56 h; elimination half-life (t1/2)=91 and 79 h and the mean residence time (MRT)=71 and 102 h. Based on the clinical response the plasma concentrations of HAL and BHAL were adequate for the treatment of uncomplicated falciparum malaria in the 6 patients.
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  • 79
    ISSN: 1432-1041
    Keywords: Fosinopril ; fosinoprilat ; CAPD ; ACE-inhibitor ; pharmacokinetics ; pharmacodynamics ; peritoneal dialysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and pharmacodynamics of fosinoprilat, the diacid of fosinopril sodium, a new angiotensin-converting enzyme (ACE) inhibitor, were investigated after the oral administration of 10 mg of fosinopril sodium to 6 chronic ambulatory peritoneal dialysis (CAPD) patients. The results from 1 patient are reported separately because of the presence of concomitant liver dysfunction. The mean t1/2, Cmax, tmax, and AUC values for 5 of the CAPD patients were 19.5 h, 202 ng·ml−1, 4.8 h, and 3.19 μg·h·ml−1, respectively. Values for 1 CAPD patient with liver dysfunction were t1/2 of 65.4 h, Cmax of 182 ng·ml−1, tmax of 9 h, and AUC of 18.1 μg·h·ml−1. Peritoneal clearance of fosinoprilat was negligible, ranging from 0.07 to 0.23 ml·min−1. Serum ACE activity remained significantly suppressed at 24 and 48 h after fosinopril sodium administration with mean decreases from baseline of 94.2% and 70.6%, respectively. ACE activity was suppressed to an even greater degree in the patient with liver dysfunction, remaining 97% inhibited 72 h after drug administration. Plasma renin activity (PRA) increased and plasma aldosterone concentrations decreased following drug administration. Mean arterial pressure did not change appreciably throughout the study. Dosage reductions may not be necessary in the majority of dialysis patients.
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  • 80
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    European journal of clinical pharmacology 41 (1991), S. 171-174 
    ISSN: 1432-1041
    Keywords: Bisoprolol ; pharmacokinetics ; obesity ; blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a single i. v. dose of dlbisoprolol 0.16 mg·kg−1 ideal body weight has been studied in 8 obese women (mean weight 91 kg; 161% of ideal body weight) and 8 non-obese women (51 kg; 94% of ideal body weight). Compared to the controls, the obese subjects showed an increase in the total apparent volume of distribution (Vz) (182 vs 135 1) and a decrease in Vz per kg body weight (2 vs 2.7 l·kg−1). There was a negative correlation between Vz l·kg−1 and the percentage of ideal body weight (r=−0.672). Total body clearance was increased, but t1/2 and renal clearance was unchanged. It is concluded that tissue diffusion of bisoprolol in obese subjects is limited, despite its lipophilicity, possibly because of alteration in the blood flow to adipose tissue produced by bisoprolol.
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  • 81
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    European journal of clinical pharmacology 41 (1991), S. 175-178 
    ISSN: 1432-1041
    Keywords: Bopindolol ; pharmacokinetics ; beta-adrenoceptor blocker ; age ; hydrolysed bopindolol
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Steady-state pharmacokinetic parameters of the new, long-acting beta-adrenoceptor blocker bopindolol have been measured in 17 young and 20 elderly healthy men. The t1/2β and the AUC(0→24 h) of hydrolysed bopindolol (the active metabolite) were both increased (40% and 26%, respectively) in the elderly subjects but tmax, Cmax and CL/f were not altered. However, after adjusting the parameters to allow for the different average body weights of the two groups, Cmax and CL/f became significantly different (+29% and −30%, respectively). AUC(0→24 h) was increased by 41%. The changes of up to 41% in pharmacokinetic parameters were smaller than the alterations of 50–100% usually seen when titrating doses of antihypertensive drugs. The clinical relevance of the effects was not examined, but similar changes have been reported for other beta-blockers which did not appear to be clinically relevant and did not affect the dosage required to treat hypertension.
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  • 82
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    European journal of clinical pharmacology 41 (1991), S. 179-183 
    ISSN: 1432-1041
    Keywords: Cefadroxil ; saturable absorption ; saturable renal tubular reabsorption ; cephalexin ; competitive inhibition ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic behaviour of cefadroxil was dose-dependent in healthy male volunteers following the oral administration of single doses of 5, 15, and 30 mg · kg−1. As the dose of cefadroxil increased from 5 to 15 and 30 mg · kg−1, the peak plasma concentrations, normalized to 5 mg · kg−1, decreased significantly from 15.1 to 10.7 and 7.6 mg·l−1, while the corresponding normalized areas under the plasma concentration-time curves from 0 to 2 h decreased significantly from 1258 to 946 and 801 min·mg·l−1. When the same subjects were given 5 mg·kg−1 of cefadroxil together with 45 mg·kg−1 of cephalexin, the absorption of cefadroxil was slowed to a similar or greater extent than with the high dose of cefadroxil. Although the absorption rate decreased as the dose increased, the systemic availability of cefadroxil was essentially complete at all doses, as judged by the 24 h urinary recoveries of the antibiotic. Kinetic analysis of the plasma concentration-time curves gave the best fit with a zero-order followed by a first-order absorption process, consistent with saturable intestinal absorption of cefadroxil. The elimination rate of cefadroxil was directly related to dose and plasma concentrations, and the clearance at the dose of 5 mg·kg−1 was significantly increased by the simultaneous administration of high-dose cephalexin. The renal clearance of cefadroxil ranged from 98 ml·min·l−1 at total plasma cephalosporin (cefadroxil + cephalexin) concentrations less than 2.5 mg·l−1 to 156 mg·l−1 at concentrations greater than 40 mg·l−1. These findings are consistent with saturable active gastrointestinal absorption and renal tubular reabsorption of cefadroxil, with competitive inhibition of both processes by cephalexin.
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  • 83
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    European journal of clinical pharmacology 41 (1991), S. 245-250 
    ISSN: 1432-1041
    Keywords: Org 10172 ; Digoxin ; heparinoid ; pharmacokinetics ; pharmacodynamics ; drug interactions
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Potential pharmacokinetic and pharmacodynamic interactions between a new low molecular weight heparinoid Org 10172 (bolus injection of 3250 anti-Xa units) and digoxin (0.25 mg once daily for 8 days) were studied in 6 healthy male volunteers using an open, randomised three-way cross-over design. Digoxin produced a slight increase in clearance of anti-Xa activity from 4.3 to 4.8 ml·min−1, while plasma anti-thrombin and thrombin generation inhibiting (TGI) activity remained unchanged. Digoxin did not affect the actions of Org 10172 on the clotting tests. In the presence of Org 10172 there was a reduction in the AUC of digoxin during one dosing interval after the seventh digoxin tablet from 20 to 17 ng·ml−1·h, and a significant reduction in the average serum digoxin conentration. Since renal digoxin clearance was not significantly changed this probably might be due to a change in the non-renal clearance of digoxin. Atrio-ventricular node conduction, as measured by PR-time intervals, remained unchanged during all three treatments. In conclusion, although the pharmacokinetics of Org 10172 and digoxin were slightly changed by the combination, it is probably safe to administer Org 10172 and digoxin simultaneously. The clinical relevance of the slight decrease in plasma anti-Xa activity levels cannot yet be defined.
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  • 84
    ISSN: 1432-1041
    Keywords: Tiaprofenic acid ; children ; pharmacokinetics ; NSAID
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary. Twelve healthy children in three age groups anaesthetized for minor surgery were given a single oral dose of tiaprofenic acid (3 mg · kg−1) (TA). Seven blood samples and zero to 8 and 8 to 24 h urines were collected. TA concentrations in plasma and urine were measured by HPLC. No significant difference was found between the age groups in the kinetic parameters of TA and no correlation was found between these parameters and age; tmax=2.12h, Cmax=8.78mg · l−1, AUC(0→8 h) 33.9mg · h · l−1, AUC=39.3 mg · h · l−1, t1/2=2.35 h, Vz=0.319 l · kg−1, CL=0.094 l · h−1 · kg−1. Renal clearance was 14 ml · h−1. kg−1. 33% of the TA dose was recovered in the 24 h urine, 48% of which was conjugated, whereas in adults, TA is only found in urine as conjugates. The apparent plasma clearance was significantly higher (56%) than in 12 healthy adults given 1.5 mg · kg−1 TA. Volume of distribution and t1/2 did not significantly differ between children and adults. Since no relationship has been established between plasma TA and either efficacy or toxicity, a different dose regimen cannot be recommended in 3–11 year-old children from that in adults.
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  • 85
    ISSN: 1432-1041
    Keywords: Alprazolam ; benzodiazepines ; pharmacokinetics ; pharmacodynamics ; sublingual dosage
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We gave 12 healthy male volunteers 1 mg of alprazolam or placebo on three occasions after a standard breakfast in a double-blind, randomized, single-dose, three-way crossover study. The three trials were: (a) oral alprazolam and sublingual placebo; (b) oral placebo and sublingual alprazolam; (c) placebo by both routes. Plasma alprazolam concentrations during 24 h after each dose were measured by electron-capture gas-liquid chromatography. Peak plasma concentrations were reached later after sublingual than oral dosage (2.8 vs 1.8 h, P〈0.01). Other kinetic variables were not significantly different: peak plasma concentration, 11.3 vs 12.0 ng·ml−1; elimination half-life, 12.5 vs 11.7 h; and total area under the plasma concentration versus time curve, 197 vs 186 h·ng·ml−1. Pharmacodynamic measures showed that sublingual and oral alprazolam both produced sedation, fatigue, impaired digit symbol substitution, slowing of reaction time, and impairment of the acquisition and recall of information. These changes were initially observed at 0.5 h after dosage and lasted up to 8 h. In general the two routes were significantly different from placebo but not from each other.
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  • 86
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    European journal of clinical pharmacology 42 (1992), S. 445-448 
    ISSN: 1432-1041
    Keywords: Ethanol ; whole blood ; plasma ; total body water ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of ethanol in plasma and whole blood have been investigated and the results used to estimate the volume of total body water (TBW) by means of the dilution principle. Fifteen men (mean age 62 y) were given 0.6 g ethanol/kg body weight as an intravenous infusion over 1 h. The peak concentration of ethanol in plasma was 120 mg·dl−1 compared to 108 mg·dl−1 for whole blood. The disappearance rate of ethanol from plasma was 18.6 mg·dl−1·h−1 compared to 17.0 mg·dl−1·h−1 for the whole blood concentration-time data. The apparent volume of distribution of ethanol (Vz) was 0.54 l·kg−1 according to plasma kinetics compared to 0.59 l·kg−1 for the kinetics derived from whole blood. The mean area under the curve (AUC) was 294 mg·dl−1×h for plasma kinetics compared to 266 mg·dl−1×h for whole blood. The TBW was 40.9 l or 50.9% of body weight for the plasma concentration-time data. This agreed well with the 40.3 l or 50.1% of body weight obtained using whole blood.
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  • 87
    ISSN: 1432-1041
    Keywords: Methylprednisolone ; Rheumatoid arthritis ; bioavailability ; pharmacokinetics ; clinical response ; pulse steroid therapy
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A commercially available 1.0 g intravenous (i.v.) dosage formulation of methylprednisolone, as the sodium hemisuccinate salt (Solu MedrolR, Upjohn) was administered both parenterally and orally (pulse steroid therapy) on separate occasions, to eight elderly (mean 65 y) patients with active rheumatoid arthritis. The relative oral bioavailability of the sterol was 69.2%. Elimination of methylprednisolone was prolonged when given orally; the mean residence times were 7.23 h and 3.94 h for oral and i.v. administrations, respectively. Clinical response to pulse steroid therapy was no different with respect to route of administration. There were no significant differences in standard clinical and laboratory assessments of disease activity when the two therapies were compared. Oral administration of methylprednisolone in patients requiring high-dose pulse steroid therapy is convenient and avoids the discomfort and inconvenience associated with i.v. administration.
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  • 88
    ISSN: 1432-1041
    Keywords: Acetyl-L-carnitine ; Senile Dementia of Alzheimer Type ; pharmacokinetics ; plasma concentration ; cerebrospinal fluid concentration ; carnitine metabolism
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Acetyl-L-carnitine (ALC), a physiological component of the L-carnitine family, has been proposed for treating Alzheimer's disease in pharmacological doses. As this condition requires prolonged therapy, its kinetics has been examined after a multiple dose regimen, involving different routes of administration, in 11 patients suffering from Senile Dementia of Alzheimer Type. The study design comprised a 3-day basal observation period, sham treatment with repeated blood sampling; treatment with 30 mg·kg−1 i.v. given twice for 10 days (plasma kinetics was studied on the 7th day), and 50 days of 2.0 g/day p.o. given in three daily doses. Total acid soluble L-carnitine, L-carnitine and acetyl-L-carnitine in plasma and CSF were evaluated using an enantioselective radioenzyme assay. Short chain L-carnitine esters were calculated as the difference between total and free-L-carnitine. The plasma concentrations of individual components of the L-carnitine family did not change during the three days of the basal period, nor were they affected during the sham therapy period. Following the i.v. bolus injections, the plasma concentrations showed a biphasic curve, with average t1/2 of 0.073 h and 1.73 h, respectively. At the end of oral treatment, plasma acetyl-L-carnitine and L-carnitine short chain esters were significantly higher than during the run-in phase. The CSF concentrations paralleled those in plasma, suggesting that ALC easily crosses the blood-brain barrier. It is concluded that i.v. and oral administration of multiple doses of ALC can increase its plasma and CSF concentration in patients suffering from Alzheimer's disease.
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  • 89
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    European journal of clinical pharmacology 42 (1992), S. 95-99 
    ISSN: 1432-1041
    Keywords: Ofloxacin ; Haemodialysis ; ofloxacin metabolites ; pharmacokinetics ; multiple doses ; dosage selection ; renal failure ; adverse effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary 7 patients with end-stage renal disease on regular haemodialysis were treated orally with a loading dose of 200 mg ofloxacin and multiple maintenance doses of 100 mg per 24 h for 10 days. The pharmacokinetics of ofloxacin and its metabolites were studied at the end of the treatment period. Plasma and dialysate concentrations of ofloxacin and ofloxacin metabolites were measured by HPLC. Peak (3.1 mg·1−1) and trough levels (1.6 mg·1−1) and the AUC of ofloxacin were comparable to the values in healthy volunteers given 300 to 400 mg ofloxacin p.o. The mean half-life, determined in the dialysis-free interval (t1/2β) and during the haemodialysis session (t1/2HD), was 38.5 h and 9.9 h, respectively. Extrarenal clearance (32.7 ml·min−1) was unchanged as compared to that reported in healthy volunteers after a single dose of ofloxacin. The fractional removal by haemodialysis amounted to 21.5%. Two metabolites, ofloxacin-N-oxide and demethyl-ofloxacin, were detected in plasma. Despite prolonged t1/2β of both metabolites (66.1 and 50.9 h) and multiple doses of ofloxacin the peak concentrations of the metabolites reached only 14% and 5% of that of the parent drug, respectively. It is concluded that in patients on regular haemodialysis treatment the dosage adjustment employed resulted in safe and therapeutically favourable plasma concentrations. The observed accumulation of ofloxacin metabolites does not appear to have any toxic or therapeutic significance.
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  • 90
    ISSN: 1432-1041
    Keywords: Methotrexate ; non-steroidal anti-inflammatory drugs (NSAIDs) ; interaction ; disposition ; adverse effects ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of methotrexate in patients with rheumatoid arthritis concurrently treated with choline magnesium trisalicylate, ibuprofen, naproxen, or a non-NSAID analgesic (control treatment). The apparent systemic clearance of methotrexate was significantly reduced by all three treatments. Trisalicylate and ibuprofen both significantly reduced methotrexate renal clearance, but only the trisalicylate significantly displaced methotrexate from protein, increasing the fraction unbound by 28%. These data show that NSAIDs can affect the disposition of methotrexate, possibly increasing the potential for toxicity and necessitating dosage adjustments. However, large inter-subject variability precludes specific dosage recommendations.
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  • 91
    ISSN: 1432-1041
    Keywords: Midazolam ; pharmacokinetics ; intranasal ; intravenous ; children ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twelve children 1–5 y old were randomly assigned to receive midazolam 0.2 mg·kg−1 either by the intravenous (IV) or intranasal (IN) routes. After IN administration the rapid onset of absorption was observed (tmax 12 min). After both routes of administration the half-life was similar (2.2 h IN and 2.4 h IV). After IN administration the apparent plasma clearance and volume of distribution were about twice as high as after IV administration. The results are consistent with an estimated mean bioavailability of 55%.
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  • 92
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    European journal of clinical pharmacology 41 (1991), S. 359-361 
    ISSN: 1432-1041
    Keywords: Diabetes ; Antipyrine ; undernutrition ; drug metabolism ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In developing countries diabetics frequently suffer from varying grades of malnutrition. The combined effect of malnutrition and non-insulin dependent diabetes (NIDDM) on the drug metabolising enzyme system has been evaluated using antipyrine as a protodrug. All the patients were under treatment and their plasma glucose values were within normal limits. The AUC of antipyrine was similar in all the groups. Although none of the kinetic parameters was altered in normal diabetics, the clearance of antipyrine was decreased and its half life was prolonged, with an increase in volume of distribution, in undernourished diabetics compared to undernourished controls. The results indicate that diabetes per se may not influence antipyrine kinetics when the blood glucose is well under control, but in the presence of undernutrition, it significantly alters the disposition of the drug.
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  • 93
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    European journal of clinical pharmacology 43 (1992), S. 567-569 
    ISSN: 1432-1041
    Keywords: Mefloquine ; Tetracycline ; Thai subjects ; Thai subjects ; drug interaction ; pharmacokinetics ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of a single oral dose of mefloquine given either alone or with tetracycline has been studied in 20 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with tetracycline (1600 vs 1160 ng · ml−1), as well as a significantly reduced terminal half-life (14.4 vs 19.3 days), mean residence time (11.9 vs 16.0 days) and volume of distribution at steady state (13.3 vs 19.91 · kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 7 days was significantly increased by tetracycline (6.18 vs 4.76 μg · ml−1 · day). The changes in mefloquine disposition after tetracycline treatment are probably due to a reduction in enterohepatic recycling. The initial increase in mefloquine AUC without an apparent increase in side-effects suggests that this combination may have a place in the treatment of multi-drug resistant falciparum malaria.
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  • 94
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    European journal of clinical pharmacology 41 (1991), S. 379-382 
    ISSN: 1432-1041
    Keywords: Codeine ; paracetamol ; codeine-6-glucuronide ; pharmacokinetics ; metabolism ; partial clearance ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma and urine concentrations of codeine and its measurable metabolites were determined by HPLC in six healthy subjects after a single 30 mg oral dose of codeine either alone or after 7 doses of 1 g paracetamol 8 hourly. After codeine alone, the t1/2 (h), AUC (μmol·l−1·h) and CLR (ml·min−1) for codeine were 2.2, 0.81, and 252 respectively. These were not significantly altered by paracetamol: 2.2, 0.84, and 291 respectively. For codeine-6-glucuronide the values were 2.4, 22.0, and 29.7 respectively. These were not significantly different from those after codeine plus paracetamol: 2.4, 21.9, and 39.6. There were no significant differences between the two treatments in the apparent partial clearances (ml·min−1) of codeine to morphine (88 codeine alone, 70 codeine plus paracetamol), to norcodeine (71 codeine alone, 88 codeine plus paracetamol), and to codeine-6-glucoronide (820 codeine alone, 1022 codeine plus paracetamol). The urinary excretion of codeine-6-glucuronide, morphine, norcodeine, and codeine were not significantly different between the two treatments.
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  • 95
    ISSN: 1432-1041
    Keywords: Cyclosporine ; Hyperlipidaemia ; heart transplantation ; fenofibrate ; fenofibric acid ; pharmacokinetics ; drug interaction ; nephrotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Cyclosporine (Cy) binds to lipoproteins in plasma. In order to test if its pharmacokinetics would be modified when efficient lipid-lowering treatment is introduced, a study has been done of Cy pharmacokinetics and any interaction with the lipid-lowering agent fenofibrate in hyperlipidaemic long-term, survivors of heart transplantation. Fenofibrate 200 mg once daily significantly reduced blood lipids (cholesterol 6.5 vs 7.7 mmol/l; apoprotein B 1.2 vs 1.6 g/l) but did not modify mean whole blood Cy trough levels (113 before fenofibrate vs 103 ng·ml−1), Cmax (812 ng·ml−1 by RIA and 757 ng·ml−1 by HPLC before fenofibrate versus 865 and 741 respectively, during fenofibrate); tmax (1.6 and 1.7 h before fenofibrate versus 1.4 and 1.4 h respectively), and t1/2 (13.9 and 11.1 h versus 9.5 and 10.7 h). The only adverse effect was an increase in creatinine (157 vs 145 mmol/l). Further studies are needed to investigate the mechanism of Cy-fenofibrate nephrotoxicity and to evaluate the long-term efficiency and safety of fenofibrate after heart transplantation.
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  • 96
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    European journal of clinical pharmacology 45 (1993), S. 255-260 
    ISSN: 1432-1041
    Keywords: Ramipril ; Propranolol ; interaction ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacodynamic effects of ramipril, propranolol, and their combination, as well as the effect of propranolol on the pharmacokinetics of ramipril in 12 healthy men (age 24 (SD 6) y, weight 72 (7) kg). Propranolol and placebo, ramipril and placebo, or propranolol and ramipril were given orally for four days in a crossover, double-blind fashion. The pharmacokinetics of ramipril and ramiprilat were investigated on day 4. Effects on plasma renin activity, ACE activity, and heart rate and blood pressure both before and after a standardized exercise test were measured on days 1 and 4. On day 4 the combination reduced the mean arterial pressure by 2.8 mmHg compared with propranolol alone and by 3.7 mmHg compared with ramipril alone. Ramipril had no effect on the bradycardia induced by propranolol. Propranolol reduced exercise mean arterial pressure by 9 mmHg (day 4) and heart rate by 7 beats.min−1 (day 4) compared with ramipril; this was not affected by co-administration of ramipril. On day 4 the average plasma renin activity was not significantly higher than after the combination. ACE activity was not affected by propranolol. The pharmacokinetics of ramipril and ramiprilat were not influenced by propranolol. The combination of ramipril and propranolol has additive pharmacodynamic effects that may be useful in the treatment of hypertension.
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  • 97
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    European journal of clinical pharmacology 45 (1993), S. 275-277 
    ISSN: 1432-1041
    Keywords: Fenoterol ; Pregnancy ; pharmacokinetics ; premature labour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of the β2-adrenergic drug fenoterol, which is used as a tocolytic agent in pregnancy, has been investigated in pregnant (n=9) and nonpregnant (n=5) women during a constant rate intravenous infusion. Clearance and mean residence time were found to be 1990 (1879/2220; Median, Q25/Q75) ml/min and 9.2 (8.0/14.0) min in the pregnant and 2126 (1915/2130) ml/min and 16.6 (16.5/32.1) min in the nonpregnant women, respectively. In addition, fenoterol clearance was estimated in 88 women from a single blood sample collected at steady state during IV therapy and the effect of gestational age on clearance was studied. Clearance displayed large inter-individual variation. There was no apparent correlation between clearance and gestational age. We conclude that there is no need to adjust the dose on pharmacokinetic grounds in the course of pregnancy.
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  • 98
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    European journal of clinical pharmacology 44 (1993), S. 195-197 
    ISSN: 1432-1041
    Keywords: Cefotaxime ; Renal insufficiency ; desacetylcefotaxime ; pharmacokinetics ; children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary It is generally assumed that the renal clearance of drugs in patients with renal impairment are affected to a similar extent regardless of the type of renal disease (intact nephron hypothesis). We have studied the effect of underlying renal disease on the pharmacokinetics of cefotaxime and desacetylcefotaxime in two groups of children (ages 7 to 16 y) with varying degrees of renal dysfunction. Patients in group 1 (n=5) had intrinsic renal disease and those in group 2 (n=5) had extrinsic renal disease, as identified by the primary renal lesion. After a single intravenous dose of cefotaxime timed blood and urine samples were collected for 24 h; cefotaxime and desacetylcefotaxime were measured by HPLC. There were no significant differences between the groups in age, body surface area, urine output, creatinine clearance, total body clearance, nonrenal clearance, renal clearance, and volume of distribution at steady state of cefotaxime, and renal clearance of desacetylcefotaxime. However, the renal clearance: creatinine clearance (CLR:CLCR) ratios for both cefotaxime [1.34 in group 1 vs. 0.51 in group 2] and desacetylcefotaxime [1.58 in group 1 vs. 0.75 in group 2] were statistically significant between the two groups. Group 1 patients had an average CLR:CLCR ratio greater than 1 for both the parent compound and the metabolite, suggesting that net tubular secretion was still intact, despite a diminished glomerular filtration rate (CLCR=24 ml·min−1·1.73 m−2). In contrast, patients in group 2 (CLCR=49) ml·min−1·1.73 m−2) had an average CLR:CLCR ratio less than 1 for both cefotaxime and desacetylcefotaxime, suggesting that renal tubular transport mechanisms did not remain functional in these patients. Our findings suggest that the effect of renal insufficiency on the renal elimination of cefotaxime and its metabolite desacetylcefotaxime may depend on the cause of renal insufficiency.
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  • 99
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    European journal of clinical pharmacology 44 (1993), S. 253-258 
    ISSN: 1432-1041
    Keywords: Bioelectrical impedance ; Gentamicin ; non-invasive technique ; neonates ; predictive models ; pharmacokinetics ; plasma levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The use of bioelectrical impedance (BI) analysis as a non-invasive approach for individualising gentamicin therapy in newborn infants has been investigated in a two phase study. In Phase I, 1/impedance and length2 were identified as statistically significant predictors of the distribution volume of gentamicin (Adj R2=0.78, CV=12.42%), and length2/impedance and post-conceptual age were predictors of total systemic clearance (Adj R2=0.83, CV=14.5%), following the administration of 2.5 mg·kg−1 gentamicin to 17 neonates (gestational age (GA) 27 to 36 weeks). In a prospective validation of these relationships in an independent (Phase II) group of 27 infants (GA 26 to 41 weeks), predicted serum gentamicin concentrations were close to those achieved. Several instances of high prediction errors (predicted minus achieved levels) were observed in infants with known or suspected renal impairment and they caused significant (P〈0.05) perturbation in the bias and accuracy of the models. Daily BI measures over a four to five day period were able to detect individual changes in the fat-free body compartments, which were translated into alterations in gentamicin regimens. This simple, non-invasive and relatively inexpensive bedside technique provides a potentially valuable means to individualise gentamicin therapy without relying on the measurement of serum gentamicin concentration.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 44 (1993), S. 357-360 
    ISSN: 1432-1041
    Keywords: Famotidine ; Reflux oesophagitis ; intraoesophageal long-term pH-metry ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics, pharmacodynamic effect and clinical efficacy of famotidine were studied in 10 patients with reflux oesophagitis Grades I and II. For the pharmacokinetic studies the patients received 20 mg famotidine i. v. The half-life of famotidine was 3.8 h, the total plasma clearance was 297 ml·min−1, and a steady state volume of distribution of 1.21·kg−1 was found. For pharmacodynamic assessment, intraoesophageal pH-metry was performed without and after acute treatment with famotidine 20 mg i. v. and following 3 weeks of oral famotidine 80 mg b. d. The resultant percentage total acid exposure time (pH〈4 within 24 h) were 23.9%, 19.0% and 19.2% (median), respectively (NS). At the end of 6 weeks of oral therapy, symptomatic and endoscopic improvement had occurred in 9 and 5 patients, respectively. Our study shows that the pharmacokinetics of famotidine in patients with reflux oesophagitis is comparable to that in healthy volunteers and peptic ulcer patients. The clinical response to the treatment appeared comparable to that found after other H2-receptor antagonists.
    Type of Medium: Electronic Resource
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