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  • pharmacokinetics  (230)
  • Gas chromatography  (72)
  • Springer  (302)
  • Annual Reviews
  • Blackwell Publishing Ltd
  • 2020-2024
  • 2005-2009
  • 1990-1994  (156)
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  • 2020-2024
  • 2005-2009
  • 1990-1994  (156)
  • 1980-1984  (105)
  • 1975-1979  (41)
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  • 1
    ISSN: 1432-2285
    Keywords: Abies alba ; Abscisic acid ; Damage ; Gas chromatography ; Needles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The amount of abscisic acid (ABA) in needles of silver fir from a natural location was investigated with regard to position in the crown, damage, seasonal variation, and needle age. Because of problems of quantification of ABA in coniferous needles, which contain numerous secondary plant products, a method for reliable determination of both isomers cis-trans-ABA (c-ABA) and transtrans-ABA (t-ABA) was developed. By means of gas chromatography (GC) using an electron capture detector (BCD) and a programmed temperature vaporizer (PTV) injector complete separation of both compounds was achieved. Two different pairs of fir were investigated — in each case a damaged and a healthy tree. Needles from both trees from the first and the second pair collected in September contained 500–1100 ng c-ABA/g fresh weight (FW), and the concentrations of t-ABA varied from 400 to 700 ng/g FW. Investigations from the second pair show highest amounts of 2900 ng/g Fw c-ABA and 1800 ng/g FW of t-ABA in May and June. For the first pair a higher c-ABA content was found in needles from the top of the crown than in those from the middle and the base. This difference could not be confirmed in the analysis of the second pair. Because of the strong natural deviation no statistically significant difference between the healthy and the damaged tree was found. The first pair of firs examined showed a higher t-ABA concentration than the second one. In this case the highest amount was found in the top of the crown. Methodical mistakes during the clean-up procedure and in quantification by gas chromatography could be excluded. The presence of c- and t-ABA in the purified extract was corroborated by mass spectrometry. With regard to the seasonal variation both isomers of ABA show an unequivocal trend. The maximum concentration is achieved in May to June, whereas the content is minimal in August/September. In any case the level of t-ABA is lower than that of c-ABA. No correlation between the amount of ABA and the needle age could be established.
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  • 2
    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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  • 3
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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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  • 4
    ISSN: 1432-1041
    Keywords: Gamma-hydroxybutyric acid ; pharmacokinetics ; dose-proportionality
    Source: Springer Online Journal Archives 1860-2000
    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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  • 5
    ISSN: 1432-1041
    Keywords: Glyceryl trinitrate spray ; pharmacokinetics ; a/b-ratio ; pulmonary artery diastolic pressure ; finger pulse curve ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    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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  • 6
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    European journal of clinical pharmacology 44 (1993), S. 463-466 
    ISSN: 1432-1041
    Keywords: Benazepril ; Proteinuria ; benazeprilat ; ACE inhibitor ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    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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  • 7
    ISSN: 1432-1041
    Keywords: dDAVP ; bioavailability ; gastrointestinal tract ; healthy volunteers ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    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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  • 8
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    European journal of clinical pharmacology 44 (1993), S. 247-251 
    ISSN: 1432-1041
    Keywords: Proguanil ; Pregnancy ; Malaria ; cycloguanil ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    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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  • 9
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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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  • 10
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    European journal of clinical pharmacology 44 (1993), S. 301-302 
    ISSN: 1432-1041
    Keywords: Adriamycin ; Haemodialysis ; adriamycinol ; pharmacokinetics ; moment analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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  • 11
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    European journal of clinical pharmacology 44 (1993), S. 305-306 
    ISSN: 1432-1041
    Keywords: Atenolol ; bioavailability ; intestinal absorption ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    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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  • 12
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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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  • 13
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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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  • 14
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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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  • 15
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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.
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  • 16
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    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.
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  • 17
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    European journal of clinical pharmacology 44 (1993), S. 365-367 
    ISSN: 1432-1041
    Keywords: Ciprofloxacin ; Diazepam ; quinolone ; benzodiazepine ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of pretreatment with a seven day course of ciprofloxacin on pharmacokinetics and pharmacodynamics of an intravenous (5 mg) dose of diazepam were investigated in a group of 12 healthy volunteers in a double-blind placebo-controlled crossover study. Ciprofloxacin pretreatment significantly reduced diazepam CL (without ciprofloxacin: 19.5 ml·h−1kg−1; with ciprofloxacin: 12.3 ml·h−1kg−1). Diazepam t1/2 was also prolonged (without ciprofloxacin: 36.7 h; with ciprofloxacin: 71.1 h), but volume of distribution was unaltered (without ciprofloxacin: 1.1 l·kg−1; with ciprofloxacin: 1.1 l·kg−1). However, no significant changes were detected in psychometric tests of digit symbol substitution, tapping rate and short memory, as well as levels of concentration, vigilance and tension measured by visual analogue scales.
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  • 18
    ISSN: 1432-1041
    Keywords: Temocapril ; Liver dysfunction ; angiotensin converting enzyme inhibitor ; diacid ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six subjects with normal liver function (Group 1) and 7 patients with liver dysfunction (Group 2; mean ICGR15 value 30.5 (5.2) %; range 16 to 56) received a single oral dose of 1 mg temocapril, a prodrug-type ACE inhibitor, with preferentially excreted by the biliary route. The plasma temocapril concentrations in Group 2 at 30 min and 1 h postdose were significantly higher than in Group 1, but the difference had disappeared 2 h postdosing. Although the half life of temocapril diacid in Group 2 was significantly longer than in Group 1, there was no significant difference between the two groups in AUC, Cmax or tmax. In Group 2, urinary recovery of temocapril was significantly increased, suggesting a possible delay in the bioactivation of temocapril into the diacid, but recovery of the diacid itself was not abnormal. ACE inhibitory action in Group 2 remained unchanged. Temocapril is regarded as an ACE inhibitor the disposition and efficacy of which are little affected in patients with impaired liver function.
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  • 19
    ISSN: 1432-1041
    Keywords: Isradipine ; Diclofenac ; pharmacokinetics ; platelet aggregation ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In this open, two-period crossover study in 18 healthy male volunteers, a single oral dose of 50 mg diclofenac was administered alone and on day 7 of multiple oral dosing of 5 mg b.i.d. isradipine to assess a possible pharmacokinetic interaction. The effect of these drugs on ex vivo platelet function was also determined. Serial blood samples were obtained over 12-hour periods on three occasions: after the single diclofenac dose; after the morning dose of isradipine on day 6 and after co-administration of both drugs on day 7 of steady-state isradipine administration. Additional samples were taken at 2 h post dose for determination of ex vivo platelet aggregation. Isradipine plasma concentrations were determined by a gas chromatographic method and diclofenac plasma concentrations by an HPLC method. The pharmacokinetic characteristics of diclofenac were unaltered during co-administration. The maximum plasma concentration of isradipine was increased 19.6% during co-administration from 5.06 to 6.05 ng·ml−1. This is not expected to be of clinical importance. Isradipine's apparent total body clearance and steady-state AUC remained unchanged. Ex vivo induced platelet aggregation was not affected by any of the treatments.
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  • 20
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    European journal of clinical pharmacology 45 (1993), S. 555-558 
    ISSN: 1432-1041
    Keywords: Glucagon ; pharmacokinetics ; i.v. infusion ; intranasal spray ; intramuscular administration ; insulin-dependent diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intranasal, an intravenous infusion, and intramuscular glucagon has been studied in 5 healthy subjects and 11 patients with insulin-dependent diabetes mellitus. After infusion the elimination half-life was significantly longer in diabetics (11.9 vs 6.6 min) and the apparent volume of distribution was twice as high in diabetics (0.19 vs 0.37 l·kg−1). The metabolic clearance rates were the same in the two groups (18.9 and 21.3 ml·min−1·kg−1 in controls and in diabetics) and were about twice those previously reported. After 1 mg intranasally the Cmax of immunoractive glucagon (IRG) was similar in diabetic and in healthy subjects. Administration of a higher dose (2 mg) to diabetic patients produced a higher plasma level, although not proportionately so. The AUC after 1 mg was also similar in controls and in diabetics. The elimination half-life in both groups was similar to the value found after IV infusion; it was significantly shorter in controls (5.5 min) than in diabetics (13.8 min). In both groups, mean Cmax was significantly lower than after IM glucagon, the relative bioavailability of 1 mg intranasally vs IM injection being less than 30%. After IM administration, the Cmax and AUC of IRG in controls and in diabetic patients, were identical. The apparent elimination half-life was also similar in the two groups, and was three- to four-times longer (28.6 and 31.4 min) than after infusion or intranasal administration, possibly because estimation of the t1/2 was affected by slow release of the hormone from the site of injection.
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  • 21
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    European journal of clinical pharmacology 45 (1993), S. 563-569 
    ISSN: 1432-1041
    Keywords: Chlorpromazine ; metabolites ; N-oxide ; sulfoxide ; 7-hydroxy ; conjugates ; pharmacokinetics ; first pass metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A study was carried out in 11 healthy young men to investigate the pharmacokinetics of chlorpromazine (CPZ) after a bolus intravenous (IV) dose (10 mg) and three single oral doses (25, 50 and 100 mg), with a washout period of two weeks between doses. Plasma levels of CPZ, CPZ N-oxide (CPZNO), CPZ sulfoxide (CPZSO) and both free and conjugated 7-hydroxy-CPZ (7-HOCPZ) were measured by extraction radioimmunoassays. CPZ exhibited multicompartmental pharmacokinetics in most subjects. There was wide between-subject variability in half life (11.05 h), volume of distribution (1215 l), volume of distribution at steady state (642 l) and mean residence time (8.88 h), whereas systemic clearance was somewhat less variable (76.6 l·h−1). All metabolites were present in measurable concentrations in the plasma of 9 of 11 subjects after IV CPZ, whereas free 7-HOCPZ was not detected in the other 2 individuals. With the exception of CPZNO, the biological half lives of the primary metabolites were longer than the half life of CPZ. After oral administration, the percentage of CPZ reaching the systemic circulation intact (F%) was very low (4–38%) and dose dependant. Moreover, both within-subject and between-subject variances were very high. The maximum plasma concentration (Cmax) and area under the plasma concentration versus time curve extrapolated to infinite time (AUC) showed evidence of nonlinearity, whereas half life did not appear to be dose dependant. These data suggest that the high degree of variability in the pharmacokinetics of CPZ is a result of extensive first pass metabolism rather than variation in half life. The mean AUC for the total conjugates of 7-HOCPZ was about two fold higher than that of the parent drug or any other metabolite. This shows that phase II metabolism plays a very significant role in the disposition of CPZ. As a result, the role of CYP2D6 in the 7-hydroxylation of CPZ cannot be fully assessed without taking phase II metabolism into account.
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  • 22
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    European journal of clinical pharmacology 45 (1993), S. 585-587 
    ISSN: 1432-1041
    Keywords: Flumazenil ; benzodiazepine ; absorption ; disposition ; elderly volunteers ; pharmacokinetics ; aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In an open design, randomised, two-way cross-over study, a single 2 mg i.v. dose and a single 30 mg oral dose of flumazenil were each administered to a group of healthy young (n=6) and elderly (n=12) volunteers (male: female 2/1). Plasma samples were collected at intervals and intact drug was assayed. Both the IV and oral doses of flumazenil were very well tolerated by both age groups and no severe or unexpected adverse effects were observed. The main complaints were dizziness and headache, mainly after oral dosing, probably due to the higher Cmax and AUC following this route of administration. After 2 mg i. v. the disposition parameters in the two age groups (elderly/young) were very similar: volume of distribution (Vss): 0.88/0.901·kg−1; total body clearance (ClPL): 0.86/0.99 l·min−1; terminal elimination half-life (t1/2β): 1.02/0.91 h. After the 30 mg oral dose the mean Cmax of 87.6 ng·ml−1 (elderly) and 78.4 ng·ml−1 (young) were generally reached within 0.5 to 1 h. In 26% (elderly) and 23% (young), the absolute bioavailability of flumazenil was very similar. It is concluded that the absorption and disposition paramters of flumazenil were not significantly affected by aging.
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  • 23
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    European journal of clinical pharmacology 44 (1993), S. 27-33 
    ISSN: 1432-1041
    Keywords: Nicorandil ; vasodilator ; tolerance study ; blood pressure ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the effects of intravenous nicorandil, a mixed arterial and venous vasodilator, in 48 healthy volunteers. Nicorandil (20, 28, 39, 54, 74, 103, 144, or 200 μg·kg−1) or placebo were given over 5 min to subjects supine (16 subjects, 2 doses) or sitting (32 subjects, 1 dose) in a single-blind crossover design. Electro-cardiographic intervals, blood pressure, and heart rate were measured before and for 8 h after dosing. Blood and urine safety laboratory studies were also performed before and after dosing. All intravenous infusions of nicorandil and placebo were well tolerated and there were no clinically important safety concerns. The most frequent adverse event after nicorandil was headache (24 events by 19 subjects), although its occurrence was not strictly dose related. One subject experienced transient symptomatic hypotension (144 μg·kg−1). Mean plasma nicorandil concentrations were dose-related and fell with a half-life of 0.7 to 1.2 h. Systemic clearance and volume of distribution tended to decrease as dose increased. Sitting subjects showed marginally lower (〈20%) systemic clearances and larger values of Cmax and AUC. Nicorandil produced dose-related reductions in blood pressure, with consistent statistically significant differences from placebo after the 144 and 200 μg·kg−1 doses. The falls in blood pressure were greater for diastolic pressure and in this supine position. At 200 μg·kg−1, the mean falls in systolic/diastolic pressures (mm Hg) during the first hour were 10.9/14.7 supine and 6.1/9.1 sitting; systolic pressure returned to baseline after 8 h and diastolic pressure after 4 h. Heart rate increased transiently (mean peak increase of 17–24 bpm at the end of the 144 and 200 μg·kg−1 infusions). Blood pressure and heart rate changes over time were statistically significantly correlated with plasma nicorandil concentrations. Individual areas under the blood pressure and heart rate change curves likewise correlated with plasma concentration curve areas.
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  • 24
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    European journal of clinical pharmacology 44 (1993), S. S31 
    ISSN: 1432-1041
    Keywords: Cefmenoxime ; Renal failure ; continuous haemofiltration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The elimination of cefmenoxime after single and repeated i. v. dosing was studied in 12 patients with severe renal failure and sepsis during continuous haemofiltration. More than 30 % of the drug was found in the filtrate. The sieving coefficient (S) was 0.54. Vss % was unchanged 0.311 · kg−1 in comparison with patients with normal renal function, whereas the mean t/12ß was prolonged to about 16 h, and total clearance was reduced 20.8 ml · min−1 · 1.73 m−2. Once daily administration of 1 g cefmenoxime is suggested as the appropriate dose under such circumstances.
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  • 25
    ISSN: 1432-1041
    Keywords: Oxprenolol ; β-adrenoceptor blockade ; circadian rhythm ; haemodynamics ; pharmacokinetics ; exercise ; healthy volunteers ; kinetic-dynamic model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the effect of dosage time of oxprenolol (Trasicor®) on its pharmacokinetics and pharmacodynamics in six healthy volunteers. The drug effects measured were heart rate and systolic blood pressure during exercise. Oxprenolol was taken orally at 08.00 h, 14.00 h, 20.00 h, and 02.00 h in randomized order, with 1 week between successive doses. There were differences in the pharmacokinetics of oxprenolol for the ratio between the apparent volume of distribution and systemic availability (P=0.04) and for elimination half-life (P=0.006). Both were lowest after administration at 14.00 h (163 (77) l and 1.2 (0.6) h; mean (SD)) and highest after administration at 02.00 h (229 (100) l, and 1.7 (0.6) h). The systolic blood pressure during exercise before oxprenolol did not vary with dosage time, but heart rate during exercise before intake was lowest before dosage time 08.00 h and highest before dosage time 20.00 h (P=0.03). The time-course of heart rate during exercise after oxprenolol was described by a model that incorporated the factors drug concentration and spontaneous diurnal variation. EC50 and Emax did not vary between dosage times. The spontaneous diurnal variation in heart rate during exercise was unaffected by oxprenolol, leading to an apparently greater effect of oxprenolol during the night than during the day.
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  • 26
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    European journal of clinical pharmacology 44 (1993), S. S53 
    ISSN: 1432-1041
    Keywords: Quinapril ; Renal failure ; quinaprilat ; haemodialysis ; ACE inhibitor ; pharmacokinetics ; pharmacodynamics ; peritoneal dialysis ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and pharmacodynamics of the ACE inhibitor quinaprilat have been studied in six chronic haemodialysis (HD) patients and in six patients undergoing continuous ambulatory peritoneal dialysis (CAPD) after a single oral dose of 2.5 mg quinapril. Mean tmax and Cmax values (SEM) for quinaprilat in interdialytic HD patients were 4.0 (0) h and 84 (8.4) ng · ml−1 respectively, and they did not differ significantly from those in CAPD patients (4.7 (0.7) h and 64 (5.7) ng · ml−1). Elimination half lives were 30 (10.1) h (HD) and 34 (7.3) h (CAPD). Cmax, tmax, t/12, and AUC were increased and CL was decreased compared to data reported previously after giving 2.5 mg to healthy subjects. Peritoneal clearance was calculated as 0.1 (0.1) ml · min−1, thus less than 0.5 % of the dose were removed within 24 h by CAPD. ACE activity was suppressed by more than 93 % between 4 and 24 h postdose (P 〈 0.001). It decreased in both groups with increasing plasma quinaprilat levels. Angiotensin II concentration compared to baseline was significantly decreased at 4 hours (−30.4±10 %) and 24 h (−30±9.9 %) (P 〈 0.05,n=11), while active plasma renin concentration was still significantly increased at 48 h postdose (+60.2±14.5 %,P 〈 0.01). Mean arterial pressure 24 h postdose was significantly (P 〈 0.05) decreased in HD (−12 mm Hg) and CAPD patients (− 20 mm Hg). Only two patients reported unwanted effects (fatigue, dizziness, nausea, and weakness). In conclusion, due to its long lasting effect on ACE activity and on blood pressure in terminal renal failure a starting dose of quinapril 2.5 mg o. d. may be used in hypertensive HD and CAPD patients.
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  • 27
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    European journal of clinical pharmacology 44 (1993), S. 361-364 
    ISSN: 1432-1041
    Keywords: Tulobuterol ; β2-adrenoceptor agonist ; aerosol inhalation ; transdermal delivery ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of tulobuterol given transdermally or by aerosol inhalation in healthy male volunteers. Tulobuterol was rapidly absorbed after inhalation, with a tmax of 0.8–1.5 h. The Cmax and the AUC increased linearly with dose. Tulobuterol was well absorbed after transdermal administration, with an absorption lag-time of about 4 h. The Cmax and AUC increased linearly with dose and the tmax was about 9–12 h. The mean percentage of drug absorbed during the application of a patch for 24 h was 82–90% after a single dose and 82–85% during repeated dosing. The mean urinary recoveries as unchanged drug after a single inhalation and patch application were 3–4% and 5–6% respectively. Tulobuterol did not accumulate during repeated inhalation or transdermal application. It was well tolerated, except for an increase in heart rate of 10–20 beats · min−1 after five repeated applications of a 4 mg patch.
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  • 28
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    European journal of clinical pharmacology 44 (1993), S. 387-389 
    ISSN: 1432-1041
    Keywords: Flosequinan ; Congestive heart failure ; elderly ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have investigated the pharmacokinetics of the direct vasodilator flosequinan in elderly patients with congestive heart failure. Eight patients received a single dose of 50 mg, and 8 patients received once-daily treatment with 25 mg for two weeks. In the single dose study, the tmax of flosequinan was 2.5 h, Cmax was 1.17 μg · ml−1 and t1/2 was 5.63 h. The tmax of the metabolite BTS 53554 was 20.3 h, Cmax was 1.44 μg · ml−1 and t1/2 was 62.0 h. BTS 53554 accumulated gradually in the 14-day repeated dose study and steady-state was reached after approximately 2 weeks. Flosequinan was not found to accumulate. Adverse reactions were not observed in either the single or repeated dose study. It is advisable to consider renal function and body weight when flosequinan is to be administered to elderly patients with congestive heart failure. The initial dose should be 25 mg.
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  • 29
    ISSN: 1432-1041
    Keywords: Metoprolol ; controlled-release formulation ; hydrochlorothiazide ; pharmacokinetics ; pharmacodynamics ; healthy volunteers ; efficacy
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied a controlled-release formulation containing metoprolol 100 mg and hydrochlorothiazide 12.5 mg. We compared the pharmacokinetics of both substances and the pharmacodynamics of metoprolol with those of a conventional combination tablet. The controlled-release formulation gave less variable plasma metoprolol concentrations, Cmax 138 nmol·l−1 and Cmin 74 nmol·l−1, whereas for the conventional formulation the mean Cmax of metoprolol was 629 nmol·l−1 and the Cmin 20 nmol·l−1. Despite lower relative systemic availability (68%) for metoprolol from the controlled-release formulation and a smaller AUC, metoprolol from the controlled-release formulation produced a greater total effect, calculated as the area under the curve of the effect on exercise heart rate vs. time (303 vs. 259%·h; P〈0.05). Hydrochlorothiazide was rapidly absorbed from both formulations and the plasma concentration profiles were almost superimposable. Controlled-release metoprolol with hydrochlorothiazide combines effective β1-adrenoceptor blockade for 24 h without affecting the pharmacokinetics of hydrochlorothiazide.
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  • 30
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    European journal of clinical pharmacology 13 (1978), S. 275-284 
    ISSN: 1432-1041
    Keywords: Diazepam ; pharmacokinetics ; pregnant women ; plasma clearance ; blood/plasma concentration ratio ; placental transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of diazepam has been studied in pregnant women at parturition. The plasma concentration of diazepam was monitored for at least 3 days in 18 women who received a single intravenous injection of 10 mg during the 10 h-period prior to delivery. Fourteen mothers had uneventful puerperia (Group I) and in 13 of these cases there was a pronounced postnatal increase in the plasma concentration of diazepam. The terminal phase half-life (t1/2) was significantly greater for Group I (mean = 65 h; range = 24–114 h) than for age-matched non-pregnant patients (mean = 29 h; range = 18–44 h from literature). The prolonged t1/2 appeared to be related to changes in the distribution of diazepam and not to a reduction in hepatic elimination since the total plasma clearance (Cltp) in these 14 pregnant patients (mean = 28 ml/min; range = 18–43 ml/min) was not reduced compared to that reported for non-pregnant controls (mean = 30 ml/min; range = 22–45 ml/min). Four mothers underwent postnatal surgery for tubal ligation (Group II) and the plasma concentration-time profiles for this group did not show the same postnatal phenomenon as did the profiles obtained for Group I. The t1/2 for Group II was shorter (mean = 31 h; range = 24–37 h) than for Group I and similar to that for the non-pregnant controls. The Cltp for Group II was greater (mean = 56 ml/min; range = 48–63 ml/min) than for both Group I and non-pregnant controls. These results suggest that delivery alters the disposition of diazepam and is generally associated with a postnatal re-distribution of diazepam into the systemic circulation. The blood/plasma concentration ratio was determined in 9 patients (mean = 0.62; range = 0.54–0.77). There was no difference in the total blood clearance between the pregnant patients of Group I and the non-pregnant controls. In most cases the umbilical venous plasma concentration (Cpuv) of diazepam was greater than the peripheral maternal venous plasma concentration (Cpmv) at delivery. The foetus appears to constitute a slowly equilibrating tissue-group in which diazepam does not reach equilibrium with the maternal systemic circulation for at least 5–10 h at which time the diazepam concentration in maternal and foetal plasma is similar.
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  • 31
    ISSN: 1432-1041
    Keywords: p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations and bioavailability of clofibrinic acid have been estimated under conditions approaching the steady-state during a ten-day period of administration as clofibrate or as a calcium clofibrinate-carbonate combination (1:1 w/w) at a dosage interval of 12 h. Formulation — related differences in bioavailability were not significant, and the 95% confidence limits of these differences were within −2% to +8% of the mean for the reference formulation of clofibrate. The mean steadystate plasma concentrations of clofibrinic acid measured on the tenth day of dosing were 116 µg/ml±22 S.D. and 119 µg/ml±23 S.D. after administration of 885 mg as clofibrate and the calcium clofibrinate-carbonate combination respectively. The peaks of mean plasma concentrations were 70 µg/ml±15 S.D., 119 µg/ml±32 S.D. and 131 µg/ml±26 S.D. on the first, fifth and tenth day of dosing with clofibrate, and 62 µg/ml±13 S.D., 127 µg/ml±S.D. and 143 µg/ml±25 S.D. on the corresponding days of dosing with the calcium clofibrinate-carbonate combination. After the last dose on the tenth day of dosing, the mean apparent half-lives of elimination of clofibrinic acid from plasma were 24.2 h±4.4 S.D. and 25.5 h±3.2 S.D. after administration of clofibrate and the calcium clofibrinate-carbonate combination respectively.
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  • 32
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    European journal of clinical pharmacology 13 (1978), S. 69-72 
    ISSN: 1432-1041
    Keywords: Phenazone ; pharmacokinetics ; hydrocortisone ; elimination rate ; distribution volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of a high plasma concentration of hydrocortisone on the metabolism of phenazone in humans has been studied. Two series of experiments were carried out, Group A to demonstrate any enzyme-inducing effect of hydrocortisone, and Group B to study the immediate effect of hydrocortisone on the metabolism of phenazone. 9 subjects (Group A) received a total 250–400 mg hydrocortisone i.m. twice daily for three days and the 24-hour elimination of phenazone was studied before and afterwards. In a further 5 subjects (Group B) the elimination of phenazone was examined during administration of hydrocortisone or placebo. The elimination rate and the apparent volume of distribution of phenazone remained unchanged under both experimental conditions.
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  • 33
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    European journal of clinical pharmacology 13 (1978), S. 97-101 
    ISSN: 1432-1041
    Keywords: Clonidine ; plasma level ; pharmacokinetics ; steady state ; urinary excretion ; side-effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single oral dose of clonidine 300 µg was administered to 8 healthy, normotensive subjects and the time course of its plasma concentrations was followed for 24 h. The plasma concentration of clonidine rose to a peak of 1.17±0.12 ng/ml at about 2 h: the absorption half-life was 0.6±0.2 h. Elimination followed first order kinetics with a half-life of 7.7±2.0 h. The correlation between the two most common side-effects of clonidine, sedation and dryness of the mouth, with the time course of its plasma concentrations was highly significant, p〈0.01. All the subjects complained of severe sedation. During continuous administration of clonidine (75 µg t.i.d.) for one week a steady state serum level of 0.30–0.35 ng/ml was achieved. One 75 µg tablet of clonidine raised the serum level to about 0.69±0.13 ng/ml in two hours. After cessation of dosing, the serum level declined with a half-life of 7.5±1.5 h. The urinary excretion of unchanged clonidine was found to be about onethird of the administered dose in 24 h during continuous administration and in the first 24 h after the single oral dose.
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  • 34
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    European journal of clinical pharmacology 14 (1978), S. 203-212 
    ISSN: 1432-1041
    Keywords: Mepivacaine ; pharmacokinetics ; neonates ; healthy adults ; metabolism ; renal excretion ; lignocaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and metabolism of mepivacaine has been studied in premature neonates dosed subcutaneously and in healthy adults dosed intravenously. The pharmacokinetics of mepivacaine in four neonates (N) was compared with that in six adults (A). Newborns had a significantly longer terminal phase half-life than adults (N mean 8.69 h; A mean 3.17 h). Total plasma clearance normalized on body weight was significantly smaller in neonates (mean 2.34 ml/min/kg) than in adults (mean 5.47 ml/min/kg), as was the hepatic blood clearance (N mean 1.37 ml/min/kg; A mean 5.10 ml/min/kg). The renal plasma clearance, however, was significantly greater in neonates (mean 0.76 ml/min/kg) than adults (mean 0.20 ml/min/kg). There was an average six-fold increase in the fraction of the dose excreted unchanged in newborns (mean 43.3%) compared to adults (mean 7.1%) with acidified urine (pH 5.5–6.0). There was significantly more of the mono-N-demethylated metabolite of mepivacaine excreted by newborns (mean 11.4%) than by adults (mean 2.2%), but their capacity to carry out aromatic hydroxylation of mepivacaine was negligible. These results for mepivacaine were compared with those previously reported for lignocaine in premature infants. The immaturity of hepatic function appears to have diminished more profoundly the ability of premature infants to metabolize mepivacaine than lignocaine. These findings are discussed in terms of perfusion theory of hepatic drug elimination.
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  • 35
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    European journal of clinical pharmacology 14 (1978), S. 143-147 
    ISSN: 1432-1041
    Keywords: Children ; leukemia ; high-dose methotrexate ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intravenous high-dose methotrexate were studied in two groups of children being treated for malignant diseases, mostly acute lymphatic leukemia. The peak serum level of methotrexate of 2.32·10−5 mol/l was found in children given 500 mg methotrexate/m2 by a 24 h infusion, and another group given 2790 mg/m2 during a 6 h infusion had serum levels as high as 2.16·10−4 mol/l. The decay of serum concentration of methotrexate after completion of the infusion followed a diphasic curve, with an initial serum half-life of 4.8 h, followed by a second half-life of 34.4 h at distribution equilibrium. The apparent volume of distribution was 56.8 litres/m2. Significant levels of methotrexate were found in cerebrospinal fluid, but penetration into cerebrospinal fluid was slow. Urinary excretion of methotrexate was considerable. Four to five days after commencement of the infusion, urinary concentrations of methotrexate still exceeded the serum levels.
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  • 36
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    European journal of clinical pharmacology 14 (1978), S. 335-340 
    ISSN: 1432-1041
    Keywords: Drug binding to muscle ; interindividual differences ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Binding of 22 drugs to human muscle tissue has been determined by ultrafiltration. All drugs tested were bound, the bound fraction ranging from 13% (aminophenazone) to 〉98% (desipramine). Both linear and nonlinear binding was observed. For chemically related substances, binding to muscle tissue correlated with plasma binding and lipid solubility. There were significant differences in binding to muscle from different individuals. With respect to pharmacokinetics of drugs, it is suggested that binding to muscle tissue may be at least as important as plasma binding.
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  • 37
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    European journal of clinical pharmacology 21 (1982), S. 287-291 
    ISSN: 1432-1041
    Keywords: tolmesoxide ; hypertension ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Tolmesoxide is a new, direct-acting vasodilator drug for use in the management of both hypertension and cardiac failure. In 6 essential hypertensives inadequately controlled by combined β-blocker and diuretic therapy (average supine blood pressure 178/103 mm Hg) the addition of tolmesoxide (300–900 mg daily) was associated with a significant improvement in blood pressure control (average supine blood pressure 161/89 mmHg). The effect of food on the pharmacokinetics and pharmacodynamics of tolmesoxide have also been studied because, particularly at higher doses, the drug has been associated with upper gastrointestinal upset and it has been empirically recommended that it be taken with food. The blood pressure and heart rate responses were not significantly different when tolmesoxide was taken fasting or with food. Food resulted in a significant reduction in the peak plasma tolmesoxide concentration (2.14 µg/ml compared to 2.97 µg/ml) and a significant increase in the time to reach peak plasma concentration (1.67 h compared to 0.63 h). Although there was no impairment of its hypotensive effect, food significantly altered the pharmacokinetics of tolmesoxide and may therefore be useful in reducing the gastrointestinal disturbance associated with its use. In the treatment of inadequately controlled hypertension, tolmesoxide has a limited role as an alternative vasodilator.
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  • 38
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    European journal of clinical pharmacology 21 (1982), S. 307-310 
    ISSN: 1432-1041
    Keywords: piretanide ; renal failure ; high dose ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of piretanide was studied in patients with renal failure. After oral administration of a high dose of piretanide (96 mg), the pharmacokinetic parameters were: elimination rate constant 0.346±0.072 h−1, half life 2.00±0.35 h, and total plasma clearance 119.55±35.90 ml · min−1. Compared to the values obtained in adults with normal renal function, these results show a decrease in total plasma clearance, but conservation of the metabolic clearance which amounts to 45% of the total clearance in the healthy adult.
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  • 39
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    European journal of clinical pharmacology 21 (1982), S. 397-402 
    ISSN: 1432-1041
    Keywords: ergotamine ; migraine ; radioimmunoassay ; clinical effects ; adverse effects ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The systemic availability of ergotamine after a single therapeutic oral or rectal dose was studied using a radioimmunoassay during the headachefree state in 24 patients suffering from migraine. Plasma concentrations of the drug were compared with anamnestic data about its clinical effects in the same patients. Among 12 patients with a good therapeutic response to medication, the mean plasma ergotamine levels stayed in the range 0.20 to 0.50 ng/ml for 6h. Their mean plasma levels at 30 min (0.33ng/ml) and 1h (0.40ng/ml) were significantly higher than those (0.06 and 0.08ng/ml, respectively) in 9 patients with only a moderate therapeutic response. In 9 patients with a moderate and 3 with a poor therapeutic response, the mean plasma level generally stayed below 0.10ng/ml. The mean peak concentrations in moderate (0.13 ng/ml) and poor (0.11ng/ml) responders appeared later (at 3h) than in good responders (at 1h). Side effects of the medication appeared to be associated with relatively low plasma levels of ergotamine and also with delayed maximum plasma concentrations of the drug. The present results suggest that the time of the maximum plasma drug level is an important determinant of the clinical effects of ergotamine, and that a good therapeutic response may be expected if a plasma ergotamine level of 0.20ng/ml or more is achieved within 1 hour after oral or rectal administration.
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  • 40
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    European journal of clinical pharmacology 21 (1982), S. 343-350 
    ISSN: 1432-1041
    Keywords: orphenadrine ; single dose ; multiple doses ; bioavailability ; pharmacokinetics ; N-demethylorphenadrine ; metabolism ; dog ; man
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of orphenadrine were measured by a specific gaschromatographic method in 5 healthy male volunteers after a single oral dose of orphenadrine hydrochloride 100mg. The single dose pharmacokinetic profile of orphenadrine was evaluated from these data. The elimination half-life ranged from 13.2–20.1 h after the commercial tablet formulation. Plasma concentrations, determined in volunteers and patients under different conditions of repeated oral administration of the same formulation of orphenadrine hydrochloride exceeded the theoretical values, predicted from the single dose pharmacokinetics, by a factor 2 to 3. The elimination half-lives after discontinuation of treatment showed a 2 to 3-fold increase over the single dose values. This demonstrates a clear discrepancy between the multiple and single dose pharmacokinetics of orphenadrine. Experiments in dogs suggested competition for biotransformation between orphenadrine and its metabolite N-demethylorphenadrine. Product inhibition of this type could explain the observed discrepancy.
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  • 41
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    European journal of clinical pharmacology 22 (1982), S. 273-279 
    ISSN: 1432-1041
    Keywords: amoxycillin ; i.v. administration ; pharmacokinetics ; two- and three-compartment models
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic characteristics of amoxycillin were studied in healthy volunteers after intravenous injection of 250 mg, 500 mg and 1,000 mg, and infusion of 2 g and 5 g. Serum concentrations were fitted using either bi- and tri- exponentional equations. Comparison of the regression curves obtained revealed that the three-compartment model gave a better fit to the serum concentration versus time curve. It was evident that there was a third, slow, dose dependent phase of disposition. This result has been confirmed by the fact that the terminal half life of amoxycillin on cessation of a continuous infusion is significantly greater than after acute administration.
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  • 42
    ISSN: 1432-1041
    Keywords: indapamide ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Two formulations of indapamide tablets (2.5 mg) were given as a 5.0 mg dose and the subsequent blood levels were compared to those obtained after administration of a 5.0 mg solution. The study was conducted as a randomized three-way crossover design using healthy male volunteers. The drug was well tolerated by all the subjects involved. The area under the blood concentration versus time curve, extrapolated to infinity was essentially the same for all three formulations (4.2, 4.7, and 4.4 µg-h/ml). Statistical comparison of the blood levels from the two tablets showed that one tablet had a significantly greater maximum blood concentration (263 vs 231 ng/ml) and a significantly shorter time of maximum blood concentration (2.3 vs 3.5 h). Cmax (333 ng/ml) and tmax (0.7 h) values for the solution were significantly higher than either tablet. The average half-life (β-phase) for all three formulations was 15 h, while the average systemic clearance was 20 ml/min. Indapamide has a low clearance rate and there was no evidence that the drug undergoes a first-pass effect.
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  • 43
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    European journal of clinical pharmacology 22 (1982), S. 257-264 
    ISSN: 1432-1041
    Keywords: TRIS buffer ; metabolic acidosis ; pharmacokinetics ; cellular uptake ; renal excretion ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To investigate the pharmacokinetics of TRIS, an infusion of the buffer was given to 6 healthy volunteers (121 mg/kg=1 mmol/kg; pH 7.4) and to 20 patients suffering from metabolic acidosis (109–376 mg/kg; pH 10.9). The drug exhibited two-compartment characteristics in volunteers (t0.5,β=5.6 h) and patients with intact renal function (t0.5,β=16.3–45.6 h). The final volume of distribution (Vβ) indicated uptake into tissues, but equilibration between body compartments was slow. Mainly unchanged TRIS was eliminated by the kidney; 82% of the administered dose was recovered from 24 h-urine of healthy subjects. In the patients a linear correlation between creatinine-clearance and TRIS-clearance was observed, the latter always being somewhat greater than the former. Only insignificant amounts of the drug were found in bile and gastric juice. In anuric patients the plasma concentration of TRIS declined monoexponentially, with a half-life between 10 and 58 h. Haemodialysis or haemofiltration did not influence this process. From the data it seems questionable whether cellular uptake of TRIS is an important factor in the therapy of intracellular acidosis, but the possibility of drug accumulation must be borne in mind if repeated doses are given to the same patient.
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  • 44
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    European journal of clinical pharmacology 23 (1982), S. 75-80 
    ISSN: 1432-1041
    Keywords: psoriasis ; 8-methoxypsoralen ; food influence ; suction blister fluid ; serum ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food on the kinetics of 8-methoxypsoralen (8-MOP) in serum and suction blister fluid was evaluated in a cross-over study in 19 psoriatic patients under PUVA treatment. The peak serum concentration of 8-MOP was reached 1.5 h after ingestion on an empty stomach, and in suction blister fluid the maximum concentration was already present in the first sample taken after 2 h, the time when UVA radiation was given. The postprandial kinetics of 8-MOP in serum and suction blister fluid differed, the highest levels being reached, respectively, at 2.4 and 3 h after intake, i.e. in both body fluids after irradiation had started. The side effects of 8-MOP, such as nausea and dizziness, in the two groups were similar. The present results indicate that to optimize the therapeutic effect of PUVA in individual patients, 8-MOP should be given on an empty stomach.
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  • 45
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    European journal of clinical pharmacology 23 (1982), S. 189-195 
    ISSN: 1432-1041
    Keywords: befunolol ; propranolol ; pharmacokinetics ; pharmacodynamic effects ; beta-adrenoceptor blocking agent
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Repeated doses of a new β-adrenoceptor blocking agent, befunolol, were administered orally to adult male volunteers for a cross-over comparison with propranolol. The β-adrenoceptor blocking activity of befunolol was greater than that of propranolol when assessed by the percentage reduction in exercise-induced tachycardia. The elimination half-life of drug was significantly prolonged on repeated administration of propranolol, but not of befunolol. The percentage reduction in exercise-induced tachycardia was highly correlated with the log plasma level of each drug. Both drugs produced a significant reduction in pre-exercise systolic and diastolic blood pressure, and significant attenuation of exercise-induced rise in systolic blood pressure.
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  • 46
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    European journal of clinical pharmacology 23 (1982), S. 235-240 
    ISSN: 1432-1041
    Keywords: ergotamine ; pharmacokinetics ; migraine ; plasma drug levels ; i.v. administration ; i.m. administration ; bioavailability
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of ergotamine has been investigated in migrainous patients using a new, specific, sensitive HPLC assay (detection limit 100 pg/ml plasma). 10 patients were given ergotamine tartrate 0.5 mg i.v. and 5 of them received the same dose i.m. 2–3 weeks later. Blood samples were collected for up to 54 h following administration and the plasma concentration were analysed. After intravenous administration the plasma ergotamine declined rapidly, with an initial distribution half-life of 3 min followed by a mean terminal half-life of 1.86 h (range 90–155 min). The mean total plasma clearance was 11.0 ml kg−1 min−1, and the volume of distribution (Vdβ ) was 1847.6 ml kg−1. Individual t1/2β showed a positive linear correlation with the individual Vdβ . The intramuscular absorption of ergotamine was rapid and maximum plasma levels were usually obtained 10 min following administration. The biological availability was incomplete and variable at 46.6% (range 28.3–60.8%).
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  • 47
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    European journal of clinical pharmacology 23 (1982), S. 327-330 
    ISSN: 1432-1041
    Keywords: bendroflumethiazide ; cantharides plasters ; blister fluid ; plasma levels ; pharmacokinetics ; compartmental analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of bendroflumethiazide (BFT) was investigated following the oral administration of 10 mg to 3 healthy volunteers. Each subject participated twice in the study. BFT was determined in plasma and cantharides blister fluid from 1/2 to 30 h post administration. Blister fluid was obtained from blisters 10–22 h old. Plasma levels were fitted to a tri-exponential equation and the concentration of the drug in the peripheral compartment was calculated from the microscopic rate constants. In 5 of 6 cases investigated, cantharides blister fluid levels paralleled the concentration of the drug in the peripheral compartment. The mean blister fluid levels exceeded the calculated concentration in Compartment 2 1.46 fold. In one case, the blister fluid level paralleled the plasma level. This subject clearly differed from the others as more than 10 h were required for blister formation in her. The results suggest that following the administration of BFT, cantharides blister fluid behaves as part of the peripheral compartment. The possible value of studying blister fluid levels in pharmacokinetic investigations is discussed.
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  • 48
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    European journal of clinical pharmacology 23 (1982), S. 343-347 
    ISSN: 1432-1041
    Keywords: valproic acid ; fatty acids ; plasma protein binding ; pharmacokinetics ; drug metabolism
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of physiologic variations of free fatty acid levels on in vivo valproic acid plasma protein binding was studied in 6 healthy adult subjects. 14 blood samples were taken during a 12-h dosing interval at steady state while in a fed condition and also during a 27 h fast. Free fraction and total valproate concentration were determined by equilibrium dialysis and GLC, respectively. Free fatty acid levels were determined from both fresh samples and samples incubated at 37°C for 12 h, the latter in order to simulate equilibrium dialysis conditions. Fasting resulted in increased serum free fatty acid levels in all subjects, ranging from 34–182% (p〈0.01). Incubation also caused free fatty acid levels to rise, more so in fed samples (50–87%,p〈0.01) than in fasting samples (10–50%,p〈0.01). Fasting resulted in a 9% increase in the mean free fraction for all subjects combined (p〈0.01). Regression analysis of 180 sets of values for free fraction, total valproate concentration and free fatty acid level suggested that valproate concentration accounts for 17% and free fatty acid level for 37% of the variation in free fraction. Mean clearance was unchanged by fasting despite an increased free fraction suggesting decreased intrinsic clearance (i.e. decreased metabolism) of valproate under these conditions.
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  • 49
    ISSN: 1432-1041
    Keywords: L-threo-3,4-dihydroxyphenylserine ; familial amyloid polyneuropathy ; pharmacokinetics ; norepinephrine ; pressor response
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of oralL-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) was studied in 7 normal subjects and 7 patients with familial amyloid polyneuropathy. Each person swallowed a single 300 mg dose in the fasting state, andL-threo-DOPS in plasma and urine was determined by high performance liquid chromatography with an electrochemical detector after separation on a boric acid gel column.L-threo-DOPS was slowly absorbed by normal subjects; the maximum plasma concentration occurred 3 h after administration and 20% of the oral dose was recovered unchanged in the urine within 12 h. It induced a substantial elevation of plasma norepinephrine levels, the peak being attained at 5 h, but without any change in blood pressure. In the patients, the absorption and metabolism ofL-threo-DOPS were delayed, and a prolonged pressor response was observed, with a peak after 8 h. It was concluded that the effects on plasma norepinephrine and blood pressure of oralL-threo-DOPS were essentially equal to those of twice as large a dose ofDl-threo-DOPS.
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  • 50
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    European journal of clinical pharmacology 23 (1982), S. 501-504 
    ISSN: 1432-1041
    Keywords: cimetidine ; uraemia ; dosing regimen ; prediction ; computer program ; old age ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Using a recently developed computer program based on a correlation between methods to predict the elimination half-life and apparent volume of distribution of cimetidine and actual data from patients, ideal dosage regimens were generated for patients with renal impairment and for geriatric patients, together with the corresponding maximum and minimum steady state concentrations. Using the ideal dosage regimens, practical regimens with feasible dosing intervals of 6, 8 and 12 h were computed, which should result in therapeutic concentrations of 0.4 to 1.3 µg/ml. For uraemic patients and geriatric patients above the age of 75 years it would be desirable to have an additional oral 100 mg dosage form.
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  • 51
    ISSN: 1432-1041
    Keywords: amitriptyline ; imipramine ; clomipramine ; antidepressant overdose ; clinical effects ; pharmacokinetics ; cardiotoxicity ; maprotiline ; doxepine ; nortriptyline ; opipramol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twenty-nine cases of self-poisoning with antidepressants (amitriptyline, imipramine, clomipramine, maprotiline, doxepine, nortriptyline, opipramol) were examined by frequent observation of CNS effects, heart rate, blood pressure and standard ECG, 24 h-ECG-monitoring, measurement of systolic time intervals, EEG recordings and frequent measurement of serum levels of antidepressants and primary metabolites. None of the patients died. Maximum total serum antidepressant level (parent compound + desmethyl metabolite) ranged from 20 to 2200 µg/l, with concentrations above 500 µg/l in 11 cases. The serum amitriptyline concentration remained high for 3–4 days in some of the severely intoxicated patients and the decay curves were compatible with partly saturated elimination. A degree of unconsciousness and the occurrence of excitation and hallucinations were generally seen in cases with total serum antidepressant levels above 500 µg/l. Grand mal seizures occurred more frequently at high antidepressant levels, but could not be predicted from the EEG recordings. Increased heart rate and prolonged QRS- and QTc-intervals were significantly correlated with the total serum antidpressant level. 24 h-ECG-monitoring revealed no serious arrhythmias or instances of heart block. Hypotension was only seen initially in few patients. Systolic time interval measurements showed changes suggesting impaired myocardial performance (elevated PEP/LVET ratio) at intermediate (60–500 µg/l) but not high (〉500 µg/l) total serum antidepressant levels. Measurement of serum concentration in antidepressant intoxication is important for identification of patients with high serum levels and the corresponding risk of developing toxic reactions, and to exclude patients with a low concentration who do not require intensive observation.
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  • 52
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    European journal of clinical pharmacology 23 (1982), S. 1-5 
    ISSN: 1432-1041
    Keywords: clonidine ; noradrenaline ; pharmacokinetics ; arterial blood pressure ; plasma concentration
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of clonidine and its relation to blood pressure response and side effects were studied after single oral doses of 75 µg, 150 µg and 250 µg in normotensive subjects. Following oral administration, the drug was absorbed rapidly after an initial lag time of 19–22 min and peak levels were reached between 2.4 and 2.9 h. Sampling over 48 h was necessary for accurate estimation of pharmacokinetic parameters. Post-peak plasma concentration declined in a monoexponential manner and the half-life of the elimination phase ranged from 9.0 to 15.1 h. Maximum plasma concentration (Cmax) and area under curve (AUC) increased proportionally with increasing doses. Clonidine produced significant reductions in the pulse rate and a dose dependent decrease in blood pressure. Clonidine (150 µg) also produced significant reductions in plasma catecholamine levels.
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  • 53
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    European journal of clinical pharmacology 23 (1982), S. 43-47 
    ISSN: 1432-1041
    Keywords: timolol ; pharmacokinetics ; pharmacodynamics ; healthy subjects ; cardiac infarction patients ; i.v. therapy
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Disappearance pharmacokinetics, pharmacodynamics and general tolerance of i.v. timolol were compared in 12 healthy volunteers and 10 patients with a definite or proven acute myocardial infarction. The drug was administered to the patients immediately on arrival at the hospital after a median delay time of 4 h. Tolerance to the injections was good in both volunteers and patients. The study revealed disappearance pharmacokinetics that were similar in volunteers and patients.
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  • 54
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    European journal of clinical pharmacology 13 (1978), S. 41-48 
    ISSN: 1432-1041
    Keywords: Furosemide ; pharmacokinetics ; anephric patients ; metabolism ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of furosemide 40 mg i.v. were compared in 7 anephric patients and in 7 normal subjects. The average serum clearance was 66 ml/min in the patients and 219 ml/min in the normal subjects, and the corresponding weight corrected clearances were 1.33 ml/min · kg and 2.96 ml/min · kg. Binding to serum proteins was significantly decreased in the anephric subjects, in whom a significant negative correlation was found between the percentage binding and the volume of distribution VDss. In the patients, but not in the normal subjects, there was a significant positive correlation between $$V_{D_{ss} } $$ and serum clearance. Both in normal and anephric individuals 4-chlor-5-sulphamoylanthranilic-acid (CSA) was found, but there was no evidence of special accumulation either of CSA or anthranilic acid in the anephric patients. In the patients the initial increase in serum concentration of sodium and protein followed by a more conspicuous decrease were more pronounced, but none of the changes were statistically significant.
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  • 55
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    European journal of clinical pharmacology 13 (1978), S. 29-33 
    ISSN: 1432-1041
    Keywords: Microcrystalline theophylline ; chronic obstructive airways disease ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma theophylline concentrations have been measured in 9 patients with chronic obstructive airways disease following the oral administration of a microcrystalline theophylline preparation. Some measurements of FEV1 were also made. Four patients were given 375 mg as a single dose and then subsequently 375 mg stat and 125 mg 4 times daily for 3 days, (Group I). A further 5 patients took 250 mg as a single dose and then 250 mg 4 times daily for 3 days, (Group II). In both groups, following the single dose and again after the last dose of chronic administration, blood samples were obtained at frequent intervals up to 24 h for plasma drug estimation. During the 3-day course, blood samples were drawn before and 2 h after each morning dose. In Group I patients, substantial plasma theophylline concentrations were seen only after the loading dose. Thereafter, the mean concentrations before or 2 h after the morning doese were always less than 4.0 µg/ml. Trough concentrations were usually below 2.0 µg/ml. In contrast patients in Group II achieved substantially higher plasma theophylline concentrations, with mean peak concentrations always 10 µg/ml or greater, and trough concentrations greater than 5 µg/ml on at least one occasion in every subject. The elimination half-lives after chronic administration in both groups were not significantly different from those obtained after single doses. Mean drug accumulation, measured as AUCss/AUC1, was 0.87±0.07 in Group I and 0.72±0.14 in Group II, indicating that accumulation had not occurred with either regimen. The mean increase in FEV1 2 h after the administration of a single dose was 19.2% after 375 mg and 16.7% after 250 mg. These results indicate that the recommended dosage regimen for microcrystalline theophylline preparation (375 mg stat and 125 mg 4 times daily) produces inadequate plasma theophylline concentrations: 250 mg 4 times daily would appear to be likely to result in satisfactory theophylline levels in more patients.
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  • 56
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    European journal of clinical pharmacology 13 (1978), S. 365-371 
    ISSN: 1432-1041
    Keywords: Etidocaine ; pharmacokinetics ; metabolism ; neonate
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The urinary elimination of etidocaine and several of its metabolites was investigated in neonates whose mothers had received one or more doses of etidocaine during labour. The urine collection period ranged among the neonates from 21.4 to 47.0 h post-partum. The total amounts of etidocaine and its metabolites recovered in neonatal urine represented a mean of 0.12 per cent of the maternal dose. Some differences in the pattern of urinary metabolites were observed between neonates and adults. Mean half-life of elimination of etidocaine calculated from sigma-minus plots of the neonatal urinary data was 6.42 h. This is greater than that previously reported following intravenous administration of etidocaine to adults (2.6 h). The slower rate of elimination in neonates is probably due to an increased neonatal volume of distribution since there is evidence to show that etidocaine is extensively metabolised by the neonate.
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  • 57
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    European journal of clinical pharmacology 13 (1978), S. 379-383 
    ISSN: 1432-1041
    Keywords: Antipyrine ; pharmacokinetics ; phenzone ; posture ; immobilization
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a single dose of phenazone was studied in six subjects while ambulant and during bed rest for 3 days. Elimination of the drug was followed for 12 h after oral and intravenous administration. The elimination rate constant and total body clearance were significantly increased during bed rest as compared to the ambulant period, but the differences were small. The apparent volume of distribution decreased significantly. No consistent change due to bed rest was found in the rate of absorption or bioavailability of the oral dose.
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  • 58
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    European journal of clinical pharmacology 13 (1978), S. 209-212 
    ISSN: 1432-1041
    Keywords: Paracetamol ; acetaminophen ; Gilbert's syndrome ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of paracetamol after intravenous and oral administration has been studied in 6 patients with Gilbert's syndrome, and 6 healthy controls. Paracetamol clearance was significantly less in the patients (255 ml/min SE±23 ml/min) than in the normal subjects (352 ml/min SE±40 ml/min). Moreover, whilst paracetamol concentrations declined monoexponentially in the patients, the decline was biexponential in the controls. No difference in the bioavailability of 500 mg paracetamol given orally was observed between the two groups. The results suggest that not only is paracetamol elimination impaired in Gilbert's syndrome, but that its distribution kinetics are also abnormal. Both these findings could be attributed to a decrease in hepatic glucuronyl transferase activity.
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  • 59
    ISSN: 1432-1041
    Keywords: Aminopyrine ; pharmacokinetics ; 14CO2 breath test ; hepatic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time-course of aminopyrine in plasma and of14CO2 in breath was determined for 6 hours after oral administration of (14C-methyl) aminopyrine to healthy controls and to patients with hepatitis and hepatic fibrosis, cirrhosis and hepatic bilharziasis.14CO2 in breath declined about 1.8 times more slowly than aminopyrine plasma levels, which suggests the occurrence of metabolite demethylation. This was confirmed by the slow elimination of14C from plasma, the formation of14CO2 after aminopyrine had disappeared and the presence of a considerable amount of monomethyl-aminopyrine in plasma. The mean14CO2 concentration in breath was correlated with but was not proportional to aminopyrine clearance, which was attributed to individual differences in aminopyrine half-life. Both a correlation and proportionality were found when14CO2 extrapolated to zero time was used as a parameter of14CO2 production. Hepatic disease affected aminopyrine clearance to a variable extent. In the hepatitis and fibrosis group, aminopyrine clearance was affected in 2 out of five subjects. In all except one cirrhotic subject aminopyrine clearance was markedly decreased. Moreover, in three out of seven cases aminopyrine absorption was impaired, presumably due to decreased gastrointestinal blood-flow. This may produce an erroneously low14CO2 concentration in breath during the first two hours after aminopyrine administration. Hepatic bilharziasis was accompanied by very low aminopyrine clearance in all four cases. In two patients high apparent Vd values were observed, probably due to “first-pass” metabolism. Patients with ascites had Vd values within normal limits.
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  • 60
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    European journal of clinical pharmacology 14 (1978), S. 57-67 
    ISSN: 1432-1041
    Keywords: Chemotherapy ; sulfadiazine ; trimethoprim ; pharmacokinetics ; acetylation
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Sulfadiazine (SDZ) 800 mg and trimethoprim (TMP) 160 mg were given orally to 10 normal subjects and the concentration of SDZ and TMP in serum and urine was followed for 24 h. Both drugs showed a significant negative correlation between individual “peak” concentrations in serum and the body weight of the subject. Twelve hours after dosing the serum concentration was 12 to 25 µg/ml for SDZ and 0.3 to 1.1 µg/ml for TMP. Individual concentration ratios between SDZ and TMP in serum were 4.8 (1 h) – 145 (24 h), and in the urine the ratio was close to 6 throughout the 24 h collection period. The range of urinary concentrations was from 65 to 400 µg/ml for SDZ and from 13.8 to 93.4 µg/ml for TMP. The fraction acetylated SDZ/acetylated SDZ + SDZ was 21% during the 0–8 h period, 33% during the 8–15 h period and 41% during the 15–24 period. The average values for the notional volume of distribution, Vd, were 0.36±0.13 1/kg for SDZ and 1.39±0.25 1/kg for TMP. The average “t1/2” was 15.2±7.4 h for SDZ and 7.4±1.9 h for TMP. Individual subjects showed a significant correlation between the serum clearance of TMP and SDZ (p〈0.01) and also between the renal clearance of the two drugs (p〈0.05). The serum clearance was significantly correlated with the renal clearance for TMP but not for SDZ. For SDZ Vd was significantly negatively correlated with the elimination constant; for TMP no such correlation was found. The serum clearance of SDZ was significantly correlated with the percentage of SDZ which was excreted as the (presumably) acetylated compound. The renal clearance of SDZ was independent of the serum concentration of SDZ. There was a highly significant negative correlation between the renal clearance and serum concentration of TMP, as well as for “acetylated SDZ”. The renal clearance of “acetylated SDZ” averaged more than six times that of unconjugated SDZ. With increased urine flow the renal clearances of TMP and SDZ were significantly increased.
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  • 61
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    European journal of clinical pharmacology 14 (1978), S. 237-244 
    ISSN: 1432-1041
    Keywords: Furosemide ; arterial hypertension ; protein binding ; sodium excretion ; renal function ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Furosemide 40 mg was injected intravenously in 7 patients with severe hypertension and vascular complications. A two compartment, open model was used to describe the disappearance of the drug from serum. The mean serum clearance (Cls=1.83 ml/min · kg) was significantly reduced compared to the mean Cls-value of a group of normals (2.96 ml/min · kg). A significant correlation was found between Cls and mean blood pressure, as well as between Cls and renal clearance (mean Clr=0.83 ml/min · kg); extrapolation of the regression line yielded a Cls-value of 50 ml/min for Clr=0. The Clr was also significantly negatively correlated with mean blood pressure. Protein binding of furosemide was normal, except in one patient, who had considerable impairment of renal function. Apparently more than 90% of unchanged furosemide passed in urine was excreted by tubular transport. A highly significant negative correlation was found between Cls and the fraction of furosemide excreted as a glucuronide. During the first two hours, significantly less sodium was excreted by the patients than by a comparable group of normal subjects. The correlation between serum concentration of furosemide and the amount excreted of sodium was not significant, but highly significant correlations were found between the amounts of furosemide and sodium excreted by the kidney in 0–30 and 0–60 min. In all the individual patients an approximately linear relationship with wide variation in the slope was found between the cumulative excretion of furosemide and sodium from 0–30 min to 0–60 and to 0–120 min. After 120 min deviations were observed in the curves from 4 of the patients, which indicated that smaller and smaller additional amounts of sodium were excreted with constant additional amounts of furosemide.
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  • 62
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    European journal of clinical pharmacology 14 (1978), S. 267-271 
    ISSN: 1432-1041
    Keywords: Lithium ; sustained-release ; pharmacokinetics ; manic patients
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An ordinary and a sustained-release lithium carbonate preparation were administered acutely at equivalent dosage (1.80 g=24.3 mmol) in a crossover fashion to manic patients. Serum lithium levels were determined by atomic absorption spectroscopy and pharmacokinetic parameters were calculated. Maximum mean serum levels of 1.13 mmol/l and 0.78 mmol/l were achieved at 6 h and 12 h respectively with the ordinary and sustained-release forms. The mean half-lives of absorption, redistribution and elimination were 0.78 h±0.05 (SE), 5.06 h±0.23, 26.8 h±4.5 and 3.73 h±0.37 (SE), 4.42 h±0.28 and 25.6 h±5.5 for the ordinary and sustained-release forms respectively. In healthy volunteers the ordinary preparation was completely absorbed but only 85% of the sustained-release form was absorbed in the manic subjects. Lithium ion distributed into two kinetic compartments and the final compartment appeared to correspond to total body water.
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  • 63
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    European journal of clinical pharmacology 14 (1978), S. 277-280 
    ISSN: 1432-1041
    Keywords: Doxycycline ; iron ; charcoal ; enteral cycling ; man ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In order to study the intestinal interactions of doxycycline (DC) with Fe++ and charcoal, two groups of healthy volunteers were given either 200 mg or 100 mg DC in capsules at 2 p. m. and 9 p. m., and blood samples for fluorimetric assay of DC were collected for 24 h starting at 8.30 a. m. on the following morning. A 24-h-urine was also collected. The test was subsequently repeated at one-week intervals, when the volunteers also ingested either ferrous sulphate (80 mg Fe++) or charcoal (4.0 g) immediately after the zero-time sample of DC and at 3, 8 and 12 h. Charcoal completely adsorbed DC in vitro in an artificial small intestinal fluid. Ferrous sulphate or charcoal did not modify the serum level or urinary excretion of DC after the 200 mg+200 mg dose, but ferrous sulphate did reduce the 24-h urinary excretion of DC after the 100 mg+100 mg dose. The serum half-life and AUC of DC were reduced by ferrous sulphate given after the 100 mg+100 mg dose of DC. Charcoal did not modify any parameter, even after the 100 mg+100 mg dose of DC. The results do not support existence of important enteral cycling of DC. Although oral ferrous sulphate can lower the serum level and shorten the serum half-life of DC, the acute experiment suggested that a therapeutic serum level of DC can be maintained despite treatment with iron in the doses used in iron-deficiency, and charcoal in the doses used in diarrhoeic states, if the drugs are administered several hours apart.
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  • 64
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    European journal of clinical pharmacology 14 (1978), S. 69-73 
    ISSN: 1432-1041
    Keywords: Citalopram ; pharmacokinetics ; man ; steady state levels ; metabolism
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of citalopram, a potent serotonin reuptake inhibitor, and its demethylated metabolite have been determined by a specific fluorescence coupling technique during single dose experiments in volunteers and in clinical tests. Citalopram was found to have linear kinetics within the dose range investigated, which were characterized by fairly rapid absorption and slow elimination (biological half-life 1–21/2 days). Steady state levels in the range 120–340 nM (i.e. slightly above those associated with pharmacodynamic activity in animals) were attained within a week. A drug/metabolite ratio of 2–3 was recorded.
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  • 65
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    European journal of clinical pharmacology 14 (1978), S. 431-434 
    ISSN: 1432-1041
    Keywords: Timolol ; pharmacokinetics ; oral and intravenous dosing
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma kinetics of timolol administered orally and intravenously to 5 male subjects were examined. Bioavailability was reduced by 25% when the drug was taken orally. Mean plasma half-life after oral dosing was 4.86 h, and after intravenous administration it was 4.56 h; the difference was not significant. The volume of distribution was 3.5 l/k. It is suggested that timolol is little affected by the ‘first pass effect’, even though there is marked interindividual variation in availability and peak plasma level.
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  • 66
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    European journal of clinical pharmacology 21 (1982), S. 293-301 
    ISSN: 1432-1041
    Keywords: metipranolol ; deacetyl metipranolol ; pharmacokinetics ; bioavailability ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic parameters of deacetyl metipranolol were determined after i.v. infusion of increasing doses (6–25 mg) in 17 normal volunteers. In a second cross-over trial, deacetyl metipranolol 10 and 20 mg were infused in a further 10 subjects, and in a third trial another 20 volunteers received metipranolol 40 mg orally. Metipranolol is very rapidly and completely deacetylated in man, so all pharmacokinetic data refer to deacetyl metipranolol, which was assayed by gas chromatography-mass spectrometry. The pharmacokinetic analysis was performed using a recently developed model, using a volume of distribution which is variable with time. The following data were obtained after oral administration: (mean values); lag-time 7.3 min; tmax 50 min, invasion half-life 6.3 min; elimination half-life 3 h; urinary excretion of unchanged drug approximately 4% of the dose. The experiments with infusion of increasing doses, as well as the cross-over study with 10 and 20 mg i.v., showed dose-linearity of the kinetics. The respective mean half-lives of elimination were 2.6, 2.9 and 2.8 h. The mean total, renal and extra-renal clearances amounted to 1237 ml/min, 149 ml/min and 1068 ml/min, respectively. The distribution coefficient was 3.5 l/kg, and protein binding amounted to 70% within the range of therapeutic concentrations. Absolute bioavailability was found to be approximately 50% by several different evaluation procedures. Thus, the pharmacokinetic profile of metipranolol shares features of both the lipophilic and the hydrophilic groups of β-blocking agents.
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  • 67
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    European journal of clinical pharmacology 21 (1982), S. 315-323 
    ISSN: 1432-1041
    Keywords: bendroflumethiazide ; propranolol ; hydralazine ; pharmacokinetics ; thin-layer chromatography ; fluorimetry ; fixed combination product
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Bendroflumethiazide (Bft) was administered to 6 healthy subjects at 3 different dose levels (2.5, 5 and 10 mg) in a cross-over design, either as capsules (2.5 mg) or as tablets (5 mg). Its pharmacokinetics were evaluated then and following administration of a fixed combination of Bft with propranolol and hydralazine to a further 7 volunteers. Plasma and urinary concentrations of Bft were determined by a new fluorimetric — thin-layer chromotography procedure. Peak plasma levels occurred after 2–3 h and averaged 15, 27 and 45 µg/l in the three dose groups. Areas under the plasma concentration — time curves (AUC0→12), which were 75, 147 and 250 µg l−1 h respectively, and cumulative urinary recovery (20%) were independent of the dose administered and the type of formulation. Thus Bft kinetics proved to be linear within the dose range evaluated. The plasma clearance was calculated to be 505 ml/min, renal clearance 108 ml/min and nonrenal clearance 396 ml/min. Bioavailability of Bft was not altered following administration of the fixed combination. The amount of propranolol found in the circulation did not change, whereas that of hydralazine (determined as apparent hydralazine) increased by 59% when the fixed combination was administered.
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  • 68
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    European journal of clinical pharmacology 21 (1982), S. 421-425 
    ISSN: 1432-1041
    Keywords: benzodiazepine ; lormetazepam ; lormetazepam glucuronide ; transfer to milk ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The concentrations of lormetazepam and its glucuronide in plasma and milk were determined during administration of 10 daily doses of lormetazepam 2 mg (2 tablets of NOCTAMID® - 1) to five mothers delivered by Caesarian section. Their babies were breast-fed throughout the study, and the plasma levels of lormetazepam and its glucuronide were determined three times in the babies. At 12 and 24h after administration, the plasma level of lormetazepam was about 3.5 ng/ml and 1.8 ng/ml in mothers, and below 0.09 ng/ml in the children. In milk the lormetazepam concentration was below 0.2 ng/ml. The plasma level of glucuronide varied between 24 ng/ml at 12h and 11 ng/ml 24h after administration. Almost no accumulation of unchanged lormetazepam was observed (factor: 1.3). The ratio of the levels of lormetazepam in milk and plasma was estimated to be below 0.06, and for the glucuronide the ratio was 0.04. The quantity of free and conjugated active ingredient transferred to the children via breast milk was calculated to be at most 100 ng/kg, corresponding to 0.35% of the maternal dose, which is regarded as tolerable.
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  • 69
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    European journal of clinical pharmacology 21 (1982), S. 499-504 
    ISSN: 1432-1041
    Keywords: gentamicin ; malnutrition ; pharmacokinetics ; infant
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of gentamicin was investigated in normal and malnourished infants aged 4–10 months. Neither mean “elimination” nor “distribution half life” show any difference, but the volume of distribution was higher in malnourished babies, probably due to their larger total body water.
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  • 70
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    European journal of clinical pharmacology 22 (1982), S. 423-428 
    ISSN: 1432-1041
    Keywords: pindolol ; renal failure ; metabolism ; pharmacokinetics ; 14C-pindolol ; blood metabolites ; urinary metabolites
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Increased metabolism of pindolol in renal impairment has previously been suggested by pharmacokinetic calculations. The present study was a pharmacokinetic and metabolic investigation in 7 patients with severe renal impairment (endogeneous creatinine clearance below 5 ml/min). All the patients received pindolol 5 mg t.d.s. 5 days. On the sixth day, after an overnight fast, 14C-pindolol 5 mg was given orally as a solution to drink. Blood samples were taken for up to 72 h and urine was collected at intervals up to 96 h for measurement of unchanged pindolol by a fluorimetric method and total radioactivity by liquid scintillation counting. Metabolites in blood and urine were analysed after separation by HPLC. It was found that the plasma levels following a single dose of 14C-pindolol were similar to those observed in healthy volunteers, but the elimination half-life was slightly increased up to 11.5 h. The observed steady state plasma concentrations of pindolol were twice as high but they are still in the therapeutic range of 10 to 100 ng/ml. Therefore, the dose of pindolol could have been reduced by a factor 2, but the reduction was not essential. No active metabolite of pindolol was found in plasma or urine, but elimination of the metabolites was decreased. The elimination half-life following multiple doses was prolonged compared to normal and it was quite comparable to that found for the pharmacodynamic half-life in renal patients. The discrepancy between the present findings and the previous results for metabolism and pharmacodynamic half-life was probably due to the sensitivity of the fluorimetric assay of pindolol.
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  • 71
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    European journal of clinical pharmacology 23 (1982), S. 155-160 
    ISSN: 1432-1041
    Keywords: amikacin ; pharmacokinetics ; development ; neonate ; infant ; child
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition kinetics of a single i.v. dose of amikacin was studied in 6 neonates (6–25 days old), 10 infants (4–18 months) and 8 young children (3–11 years). There was a progressive change in the distribution and elimination kinetics during development. The distribution coefficient of the antibiotic averaged of 0.429, 0.320 and 0.210 l/kg in the newborns, infants and young children, respectively and serum half-life (t1/2 β) in these three groups averaged 2.812, 1.803 and 1.196 h, respectively. Significant differences in certain pharmacokinetic parameters were found between the values in paediatric patients and in adults receiving the same dose. A linear relationship was established between the distribution volume of the antibiotic and the weight of the patients, as defined by the following equation: $${\text{Vd}}_{{\text{ss}}} \left( 1 \right) = 0.976 + 1.140 \cdot {\text{TBW}}\left( {{\text{kg}}} \right);r = 0.954$$ The results suggest that a regimen of very frequent administrations should be employed in infants and young children in order to maintain a therapeutic level throughout treatment.
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  • 72
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    European journal of clinical pharmacology 22 (1982), S. 161-169 
    ISSN: 1432-1041
    Keywords: mebendazole ; hydatid disease ; Echinococcus granulosus ; hepatic disease ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentrations of mebendazole and its metabolites have been monitored in twelve patients after receiving a 10 mg/kg dose for cystic hydatid disease. The mebendazole plasma concentration-time profiles differed considerably between patients; elimination half-lives ranged from 2.8–9.0 h, time to peak plasma concentration after dosing ranged from 1.5–7.25 h and peak plasma concentrations ranged from 17.5 to 500 ng/ml. The mean peak plasma concentration of mebendazole after an initial dose (69.5 ng/ml) was lower than found in patients during chronic therapy (137.4 ng/ml). The plasma AUCTs for the major metabolites of mebendazole (methyl 5-(α-hydroxybenzyl)-2-benzimidazole carbamate and 2-amino-5 benzoylbenzimidazole) were about five times the plasma AUCT found for mebendazole in patients on chronic therapy. It is suggested that the slower clearance of these polar metabolites relative to mebendazole results from enterohepatic recycling. Since mebendazole is also highly plasma protein bound, caution should be observed in administering mebendazole to patients with liver disease. Concentrations of mebendazole found in the tissue and cyst material collected from two patients during surgery ranged from 59.5 to 206.6 ng/g wet weight.
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  • 73
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    European journal of clinical pharmacology 23 (1982), S. 173-176 
    ISSN: 1432-1041
    Keywords: melperone ; neuroleptic drug ; dose dependent kinetics ; i.m. injection ; i.v. injection ; pharmacokinetics ; oral application
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of melperone (Buronil®, Ferrosan, Sweden) was studied after administration of various parenteral and oral doses to man. After parenteral administration, the data could be fitted to a two-compartment model, but after oral dosing the distribution phase could not be separated from the elimination phase, and so an one-compartment model gave the best fit. The half-lives were about 3–4 h, except after intramuscular injection, when the half-life was about 6 h. The bioavailability of oral doses was about 60% of the intravenous injection. After the highest oral dose of 100 mg, the pharmacokinetics, expressed as AUC or Cmax, showed non-linearity, possibly due to saturation of the hepatic elimination system.
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  • 74
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    European journal of clinical pharmacology 23 (1982), S. 331-333 
    ISSN: 1432-1041
    Keywords: ketoconazole ; vaginal candidosis ; oral antimycotic ; distribution ; pharmacokinetics ; vaginal tissue concentrations
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma samples and biopsies of vaginal tissue were obtained from 23 healthy women undergoing operative sterilization, 1 to 6 h after a single oral dose of ketoconazole 200 mg. Drug concentrations in plasma and tissue, were measured by a specific gas chromatographic method. The vaginal tissue concentration averaged 2.4 times less than the corresponding plasma levels. Equilibrium between tissue, and plasma was established within 1 h after dosing, when vaginal tissue levels exceeded 1 µg/g. Ketoconazole concentrations decayed monoexponentially over the time interval studied (1–6 h), with the similar half-lives of 1.2 and 1.4 h in plasma and tissue, respectively. Following an oral 200 mg dose, a tissue concentration not less than 0.01 µg/ml was maintained over a 12 h period. This concentration has been shown to prevent outgrowth of the invasive (pseudo) mycelial form ofCandida albicans. Hence, a b.i.d. or t.i.d. dosage schedule of ketoconazole in vaginal candidosis would give continuously effective levels at the site of infection. Ketoconazole concentrations in vaginal fluid are thought to be much higher than in the tissue because of ion-trapping. The present data may explain the efficacy of oral ketoconazole in the treatment of vaginal candidosis.
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  • 75
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    Keywords: Thiamin ; thiamin monophosphate ; thiamin diphosphate ; distribution ; thiamin elimination ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The concentrations of thiamin and thiamin monophosphate and diphosphate in plasma and whole blood samples were assessed in six healthy subjects for 12 h and in urine for 24 h following an IV and PO bolus dose of 50 mg thiamin HCl. Unphosphorylated thiamin increased rapidly in plasma after IV administration and then decreased to its initial value within 12 h in all but one subject; the half-life was 96 min. Thiamin mono and -diphosphate increased moderately (56%), and decreased slowly; the half-life of diphosphate was 664 min. Within 24 h, 53% of the administered dose was recovered in the urine, indicating a restricted distribution. After oral administration, the peak thiamin concentration in plasma was reached after 53 min and the concentration then had increased to 179% of its initial value. The elimination half-life was 154 min, and only 2.5% of the given dose was recovered in the urine. The relative bioavailability of thiamin was 5.3%. A moderate amount of the administered thiamin was stored in blood. Other body tissues must play an important part, therefore, in the distribution of thiamin.
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  • 76
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    Keywords: Theophylline ; Antacids ; Asthma ; slow-release formulations ; pharmacokinetics ; drug interaction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Antacids can modify the pharmacokinetic parameters of sustained-release preparations of theophylline by changing the gastric pH. Though this has been studied with various theophylline/antacid combinations, the specific preparations investigated here have not previously been tested. The objective of the study was to assess any change in the availability of theophylline from a sustained-release preparation (SR), induced by the coadministration with an antacid. The study was designed as a double-blind randomized crossover trial in the Pneumology Departments of three general hospitals. Fifteen patients were studied. They all had stable asthma treated with theophylline and no major organ failure or gastro-intestinal lesions requiring the use of antacids. The antacide (aluminium hydroxide 800 mg and magnesium hydroxide 800 mg), or placebo, tid, was added to a stable regimen of theophylline SR bid, for 4 days, in crossover fashion. Plasma theophylline concentrations were measured before and 1,2,3,4,6,8,10,12,16 and 24 h after the morning dose of Armophylline on the fourth day of each treatment period; the maximum plasma concentration (Cmax), and time to Cmax (tmax) were noted, and the area under the 24-h time-concentration curve (AUC0–24) and mean plasma concentration (Cmean) were computed. Peak expiratory flows on the same day, before and 3, 6 and 12 h after the morning dose of Armophylline were also measured. There was no change in any of the parameters studied. The addition of the antacide to theophylline, each given according to standard clinical practice, did not modify the pharmacokinetics of the latter. This result probably can not be generalized to all pairs of sustained-release theophylline-antacid preparations.
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  • 77
    ISSN: 1432-1041
    Keywords: Prednisolone ; Rifampin ; drug-interaction ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have investigated changes in the pharmacokinetics of prednisolone caused by co-administration or discontinuation of rifampin. Serial IV pharmacokinetic studies of prednisolone (1 mg/kg) in groups of 3 patients over a 1 month period of rifampin co-treatment or after its withdrawal, revealed significant changes in the area under the curve, the total clearance, the non-renal clearance and the half-life. The changes in the pharmacokinetic parameters reached a 1.5 to 2-fold plateau after 2 weeks and the half maximal effect was attained within 5 days. Neither the volume of distribution nor the protein binding of prednisolone were significantly altered.
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  • 78
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    European journal of clinical pharmacology 44 (1993), S. 279-282 
    ISSN: 1432-1041
    Keywords: Nifedipine ; Doxazosin ; combination ; pharmacokinetics ; liver blood flow
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a single-blind study 12 normotensive men took nifedipine 20 mg (Group 1, n=6) or doxazosin 2 mg (Group 2, n=6), followed by the combination. Each subject attended on four 9-h study days for evaluation of the effects of single and multiple doses of the monotherapy and the effects of adding single and multiple doses of the second drug. Measurements of BP, HR, plasma drug concentrations, and apparent liver blood flow were recorded. The combination was generally well tolerated. BP was consistently lower with the combination than with either monotherapy: for example, average erect BP was 108/61 (Group 1) and 112/62 mmHg (Group 2) compared with 122/66 and 116/68 during steady-state monotherapy. The introduction of nifedipine in Group 2 was associated with a significant increase in liver blood flow at 1.5 h: 1560 vs 1050 ml · min−1 during monotherapy with doxazosin. There was no significant kinetic interaction. In particular, the steady-state AUC of doxazosin was unaffected by the addition of nifedipine: 257, 307, 301, and 256 ng · ml−1 · h for the 4 study days (Group 2).
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    European journal of clinical pharmacology 45 (1993), S. 383-385 
    ISSN: 1432-1041
    Keywords: Chloroquine ; Desethylchloroquine ; Blood levels ; Steady state concentrations ; pharmacokinetics ; rheumatic diseases
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a review of studies using appropriate methods for drug determinations and controlled intake, an interindividual variation in chloroquine concentrations of 2.3 to 5.6-fold was found. In our department, steady-state concentrations were evaluated in 40 patients with rheumatic diseases. The variation in whole blood concentrations was 11-fold for chloroquine and 10-fold for the desethylchloroquine metabolite. The mean ratio between desethylchloroquine and chloroquine concentrations was 0.53 and the Spearman-Rank correlation 0.92. The correlation between age and the ratio of chloroquine concentration/dose was 0.36 (P〈0.05) and the corresponding correlation for body weight was −0.43 (P〈0.05). Our data indicate that body weight and age are important independent factors for the disposition of chloroquine. However, when extensive 100-fold variations in concentrations are found between individuals we suggest that the reliability of the dose intake should be questioned.
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    European journal of clinical pharmacology 45 (1993), S. 387-388 
    ISSN: 1432-1041
    Keywords: Iron deficiency anaemia ; Phenytoin ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Iron deficiency is a common nutritional deficiency, which leads to structural functional and enzymatic changes in the body that may affect the pharmacokinetics of drugs. The present study in 7 normal volunteers and 8 adult male patients with irondeficiency anaemia (IDA) was done to investigate the effect of iron deficiency and its treatment with total dose iron (TDI) on the bioavailability of a single dose of phenytoin. Phenytoin bioavailability was investigated before and 3 and 28 days after TDI. The bioavailability parameters Cmax, tmax, AUC and 2 h phenytoin concentrations were not significantly different in anaemic patients as compared to normal volunteers before or after treatment, except for an increase in tmax 28 days after TDI treatment.
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  • 81
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    European journal of clinical pharmacology 45 (1993), S. 377-381 
    ISSN: 1432-1041
    Keywords: Midazolam ; Ephedrine ; Sauna ; pharmacokinetics ; pharmacodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of a sauna on the pharmacokinetics and pharmacodynamics of single doses of ephedrine 50 mg and midazolam 15 mg have been studied in 6 young healthy women in a placebo-controlled, double-blind study. The sauna (3 × 10 min; temperature 80–100°C; relative humidity 30–50%) modified the pharmacokinetics of both drugs: it retarded the absorption of midazolam estimated as Ka values, and it reduced the mean plasma midazolam concentrations at 2 h; ephedrine, was absorbed more rapidly and the maximum plasma concentration occurred earlier than in the control sessions. Changes in the pharmacodynamics due to the sauna were consistent with the pharmacokinetic findings: midazolam decreased flicker recognition and induced exophoria significantly less during the early sauna period than in the control session, whereas ephedrine made the volunteers subjectively more alert at that time. Later, at 2.5 and 3.5 h (1 h 20 min and 2 h 20 min after cessation of the sauna), and despite the equalisation of the plasma levels, midazolam caused significantly more exophoria after the sauna than in the control situation. This indicates an influence of a sauna on drug pharmacodynamics in the post-sauna adaptive phase. The results suggest that exposure to a sauna may alter both drug pharmacokinetics and pharmacodynamics.
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  • 82
    ISSN: 1432-1041
    Keywords: Metoclopramide ; Biliary excretion ; enterohepatic recirculation ; Nasobiliary drainages ; pharmacokinetics ; biliary obstruction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The biliary excretion and apparent oral clearance of metoclopramide (MCL) were determined after oral administration of 1 mg MCL/kg body weight to 10 patients suffering from extrahepatic cholestasis with nasobiliary tube for drainage of the common bile duct. A bilioduodenal endoprosthesis was subsequently fitted in 6 of these patients, i.e. the enterohepatic circulation was restored, and the apparent oral clearance was re-determined. Biliary excretion, comprising free MCL and the products of conjugation, accounted for less than 1% of the administered dose. In accordance with this, the median areas under the plasma concentration-time-curves AUC(0–15 h) in patients with intact and interrupted enterohepatic recirculation were of similar size. The pharmacokinetic values in patients with cholestasis (median apparent oral clearance 0.5 l·kg−1·h−1; median t1/2 4.5 h) were similar to those previously reported in patients with healthy liver function. We conclude that it is not necessary to adjust single doses of MCL in patients recovering from obstructive jaundice.
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    European journal of clinical pharmacology 45 (1993), S. 425-430 
    ISSN: 1432-1041
    Keywords: Amlodipine ; Felodipine ER ; pharmacokinetics ; blood pressure response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary This study investigated potential therapeutic differences between Amlodipine 5 mg and Felodipine ER 10 mg in 12 normotensive/borderline hypertensive subjects by comparison of the plasma drug concentration-time profiles and the blood pressure and heart rate responses. There was significantly less trough-to-peak variability in plasma drug concentrations with amlodipine with a ratio of 67%, compared to 37% for felodipine. Correspondingly there was less variability with amlodipine in the blood pressure reductions across the dosage interval. Overall, amlodipine displayed a more consistent hypotensive effect across 24 hours and lower blood pressure values at trough, i. e. 24 hours post-dose.
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  • 84
    ISSN: 1432-1041
    Keywords: Didanosine ; Metoclopramide ; Loperamide ; HIV patients ; pharmacokinetics ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of orally-administered didanosine were evaluated in 6 male and 6 female HIV seropositive patients to determine the effect of pretreatment with metoclopramide, an inducer of gastrointestinal motility, and loperamide, which retards motility. Using a randomized, balanced, crossover design, each patient received the following three treatments under fasting conditions: didanosine as a single agent, didanosine 5 min after a single 10 mg intravenous dose of metoclopramide, and didanosine 1 h after the final of 4 doses, 4 mg each, of loperamide. Serial blood and urine samples were collected for up to 12 h after each dose. Plasma and urine aliquots were analysed for intact didanosine using HPLC with UV detection. Pharmacokinetic parameter values were calculated using noncompartmental methods. The mean Cmax values were significantly greater for the didanosine single agent (2.04 μg·ml−1) and didanosine with metoclopramide (2.30 μg·ml−1) treatments than for the combination of didanosine with loperamide (1.57 μg·ml−1). The t1/2 in males was significantly greater than in females for the didanosine (1.75 vs 1.12 h, respectively) and didanosine with metoclopramide treatments (1.74 vs 1.20 h, respectively). No significant treatment or gender effects were observed for AUC or UR (urinary recovery). The pharmacokinetics of didanosine were not altered appreciably by dosing with metoclopramide. Administration with loperamide affected the rate but not the extent of absorption. There were no clinically relevant differences between males and females in the disposition of didanosine.
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  • 85
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    European journal of clinical pharmacology 45 (1993), S. 431-436 
    ISSN: 1432-1041
    Keywords: Fosinopril ; ACE inhibitors ; haemodialysis ; pharmacokinetics ; pharmacokinetics-pharmacodynamics
    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 in six haemodialysis patients. Intravenous 14C-fosinoprilat (7.5 mg), oral 14C-fosinopril sodium (10 mg) and oral fosinopril sodium (10 mg) were administered in an open-label, randomized study. Mean maximum concentration (Cmax), clearance (CL), volume of distribution at steady-state (Vss), mean residence time (MRTiv), and t1/2 values after IV administration of 14C-fosinoprilat were 2,042 μg·ml−1, 11.3 ml·min−1, 11.01, 16.3 h and 28.3 h, respectively. Following oral administration of 14C-fosinopril, mean Cmax, time to maximum plasma concentration (tmax), and fosinoprilat bioavailability values were 197 ng·ml−1, 5.2 h and 29.2 %. Para-hydroxy fosinoprilat and fosinoprilat glucuronide comprised approximately 15 % and 2 % of radioactivity recovered in faeces. Four hours of haemodialysis only cleared approximately 1.5 % of the administered dose. The maximum effect (Emax) model was fitted to the percentage inhibition of serum ACE activity vs. fosinoprilat concentration data in three patients. Emax ranged from 95.3 to 102.5 %, and IC50 (the fosinoprilat concentration required to produce 50 % of Emax) ranged from 2.6 to 4.2 ng·ml−1. Pharmacokinetic variables of the patients were similar to those in patients with moderate to severe renal dysfunction. Dosage modifications or supplemental dosing following dialysis are unnecessary.
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  • 86
    ISSN: 1432-1041
    Keywords: Nicorandil ; vasodilator ; continuous infusion ; blood pressure ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics and haemodynamic effects of nicorandil after a 12-h infusion. Nicorandil is a mixed vasodilator combining the actions of a nitrate and a potassium channel opener. Nicorandil was infused for 12 h in 21 healthy volunteers at rates of 0.05, 0.10, and 0.20 μg·kg−1·min−1 using a placebo controlled, crossover design. Systemic blood pressure, heart rate, electrocardiographic (ECG) intervals, and cardiac output (impedance cardiography) were measured supine and standing. Dose-related, steady-state plasma nicorandil concentrations occurred within 3 to 4 h. Nicorandil's pharmacokinetics were linear with dose. Four 0.20 μg·kg−1·min−1 nicorandil infusions were terminated early primarily because of moderate or severe headaches. There were no safety concerns (ECG intervals, laboratory assays). Blood pressure fell versus placebo only in the standing position and heart rate increased slightly (not significant). That is, standing blood pressure in the 6 to 12 h interval fell from baseline 8.0*/6.8, 1.6/5.1, and 9.8*/7.9* mmHg (systolic/diastolic, *=P〈0.05 versus placebo) at 0.05, 0.10, and 0.20 μg·kg−1·min−1 respectively. Cardiac output increased slightly above placebo at lower doses. Haemodynamic changes correlated poorly with plasma nicorandil concentrations. Similar total doses were less well-tolerated when extended over 12 h. We saw no evidence of pharmacodynamic tolerance to nicorandil within 12 h.
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  • 87
    ISSN: 1432-1041
    Keywords: Piperacillin ; Vancomycin ; liver transplantation ; antibioprophylaxis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of piperacillin and vancomycin used intravenously as antibioprophylaxis were measured in the plasma and bile during orthotopic liver transplantation. Piperacillin (4 g and then 2 g every 4 h) and vancomycin (1 g and then 0.5 g every 6 h) were infused in 10 patients. During vascular clamping without venovenous bypass, clearance of both antibiotics decreased in relation to renal insufficiency. During the surgical procedure, volume of distribution of both drugs increased because of fluid redistribution. The peaks of piperacillin after first, second and third administrations were respectively 314, 265 and 210 mg·l−1, while trough levels were 46.5, 55.2 and 54.5 mg·l−1. The peaks of vancomycin were 54.4, 49.6 and 40.9 mg·l−1, while first and second trough levels were 9.5 and 12 mg·l−1. These plasma concentrations were quite similar to levels reported in healthy subjects despite large blood loss and fluid replacement. However, piperacillin trough concentrations (〈64 mg/l) were too low in relation to its concentration-dependent antibacterial activity and vancomycin peak concentrations (≥40 mg/l) were slightly too high in relation to its toxicity.
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  • 88
    ISSN: 1432-1041
    Keywords: Piroxicam ; H2 receptor antagonists ; Arthritis ; drug interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A randomised crossover study was performed in subjects with rheumatoid arthritis (or other arthropathies) to investigate if any alteration in the steady pharmacokinetics of the NSAID piroxicam (a drug which is extensively metabolised via cytochrome P450) or its major metabolites occurred as a result of coadministering either cimetidine or nizatidine. Twelve females and 2 males with mean age, weight, and albumin concentrations of 58 years, 61 kg, and 40 g·L−1 respectively, completed the study. Comparisons were made between the following parameters: plasma piroxicam AUCs [AUC0-24(P)], plasma 5-hydroxypiroxicam AUCs [AUC0-24(5-OHP)], the ratio of these i.e. AUC0-24(5-OHP):AUC0-24(p), the % piroxicam daily dose excreted in urine as 5-hydroxypiroxicam (before and after glucuronidase incubation); and the mean of the steady state trough piroxicam, and 5-hydroxypiroxicam concentrations (obtained during each study phase in addition to the wash-out period). A statistically significant difference as a result of initiating either cimetidine or nizatidine was obtained only for the ratio AUC0-23(5-OHP):AUC0-24(P). This was indicative of a weak potential to inhibit piroxicam hydroxylation. No clinically significant alteration in the steady state pharmacokinetics of piroxicam occurred in these subjects as a result of cimetidine or nizatidine coadministration. Consequently it is unlikely that any adverse events would arise from these combinations.
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  • 89
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    European journal of clinical pharmacology 44 (1993), S. 501-503 
    ISSN: 1432-1041
    Keywords: Zidovudine ; Diarrhoea ; HIV ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Many patients with AIDS have gastrointestinal complaints, including the major clinical disorder of chronic diarrhoea. The pharmacokinetics of zidovudine was studied in 9 male patients with HIV infection and diarrhoea to establish whether drug absorption was impaired in them. The peak plasma concentration and AUC after a single oral dose of 200 mg, were the same as those reported in 6 healthy male volunteers (3.1 vs 4.0 μmol·l−1 and 7.2 vs 5.2 μmol·h·l−1, respectively). Since the bioavailability of zidovudine is not particularly impaired, oral zidovudine therapy can be maintained in patients with diarrhoea.
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  • 90
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    European journal of clinical pharmacology 44 (1993), S. 497-500 
    ISSN: 1432-1041
    Keywords: Nocloprost ; PGE2-analoga ; clearance ; half life ; absolute bioavailability ; pharmacokinetics ; i. v. dose ; oral dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and absolute bioavailability of nocloprost, a synthetic PGE2-analogue with cytoprotective properties, was investigated in human volunteers as a function of the dose. Ten young male volunteers received nocloprost 5 μg i. v. and 100, 200 and 400 μg p.o. in random order at weekly intervals. Serum nocloprost levels were monitored for up to 12 h after each dose, using a specific, validated assay. After nocloprost 5 μg i. v. the highest serum level of 373 pg·ml−1 was found in the first sample 5 min after injection, and the subsequent decline showed one or two phases, with half-lives of 4 and 49 min. The AUC was 89 pg·h·ml−1, the total plasma clearance was 13.2 ml·min−1·kg−1, and the volume of distribution at steady state was 0.16 l·kg−1. After oral administration the maximum serum level and AUC increased in proportion to the dose. tmax showed a wide scatter, with an average value of about 30 min independent of the dose. Although not detectable in every subject, post maximum serum levels declined biphasically, with half-lives of ca 10 and 35–40 min. The absolute bioavailability after oral administration averaged about 2% and was independent of the dose.
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  • 91
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    European journal of clinical pharmacology 44 (1993), S. 505-507 
    ISSN: 1432-1041
    Keywords: Adenosine ; pharmacokinetics ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma kinetics of adenosine was investigated in healthy volunteers after a 1 minute infusion of 2.5, 5 and 10 mg (38, 79 and 148 μg·kg−1 respectively) and after infusion of 200 μg·kg−1 in 10 min followed by 400 μg·kg−1 in 10 min. As the dose in the 1 min infusion study was increased the mean CL of adenosine decreased (10.7, 4.70 and 4.14 l·min−1, respectively), its mean half-life increased (0.91, 1.24 and 1.86 min, respectively), and the mean volume of distribution did not show any clear trend (8–13 l). After the 20 minute infusion the plasma level of adenosine reached a peak value comparable to that observed after infusion of 5 mg in 1 min (about 0.5 μg·ml−1), but the mean clearance and half-life were significantly different (12.1 l·min−1 and 0.63 min respectively). In all the subjects the plasma concentration of adenosine had returned to the baseline value in 5–15 min after the end of the infusion.
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  • 92
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    European journal of clinical pharmacology 44 (1993), S. 575-578 
    ISSN: 1432-1041
    Keywords: Pantoprazole ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma pharmacokinetics of pantoprazole have been investigated following single intravenous infusion and single oral administration at a dose of 40 mg to 12 healthy male subjects in a randomised cross-over study. Both treatments were generally well tolerated and no relevant compound-related adverse events were noted. The plasma pharmacokinetics of pantoprazole following intravenous infusion in this group of subjects were characterised by a total plasma clearance of 0.13 l·h−1·kg−1 and apparent terminal elimination half-life 1.9 h. The apparent volume of distribution estimated at steady state (0.171·kg−1) was compatible with the localization of a major fraction of the compound in extracellular water. Following oral administration as an enteric-coated tablet formulation, a variable onset of absorption was followed by rapid attainment of maximum plasma concentrations of pantoprazole. Pantoprazole was well absorbed following oral administration; the absolute systemic bioavailability of the compound was estimated as 77% (95% CI, 67 to 89%).
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  • 93
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    European journal of clinical pharmacology 44 (1993), S. 563-568 
    ISSN: 1432-1041
    Keywords: Oestradiol analogues ; 17β-oestradiol ; oestrone ; oestriol ; micronised oestradiol ; oestradiol cyclo-octylacetate ; oestradiol decanoate ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A randomised, single-blind comparative study was carried out in 9 ovariectomized women to evaluate the kinetics of single doses of three different steroid combinations: 0.150 mg desogestrel +2.0 mg micronized 17β-oestradiol, 0.150 mg desogestrel +0.500 mg 17β-oestradiol cyclo-octyl acetate and 0.150 mg desogestrel +1.0 mg 17β-oestradiol decanoate. Serum levels of 17β-oestradiol and oestrone were measured, as well as the excretion of 17β-oestradiol and its metabolites (oestrone and oestriol) in urine. In relation to the doses given, higher peak serum concentrations of 17β-oestradiol were obtained after the two fat soluble analogues, while the AUCs were similar to that after micronised 17β-oestradiol. However, there was more extensive conversion of the micronised 17β-oestradiol preparation into oestrone compared to 17β-oestradiol cyclo-octyl acetate and 17β-oestradiol decanoate. The oestrone/17β-oestradiol serum concentration ratio was approximately 2.6 before tablet intake and remained essentially unchanged after intake of 17β-oestradiol cyclo-octyl acetate and 17β-oestradiol decanoate. After micronized 17β-oestradiol however, there was a 2–3-fold increase in the ratio at Cmax and slower elimination of 17β-oestradiol from plasma, which may be due to the fact that high serum oestrone levels may serve as a reservoir, since both a metabolite and also a precursor of 17β-oestradiol. The urinary excretion of 17β-oestradiol, oestrone and oestriol was highest after oral administration of micronized 17β-oestradiol compared to 17β-oestradiol cyclo-octyl acetate and 17β-oestradiol decanoate. The time pattern of urinary excretion reflected the serum concentration profiles of the preparations given.
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  • 94
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    European journal of clinical pharmacology 44 (1993), S. 579-582 
    ISSN: 1432-1041
    Keywords: 2-Chloro-2′-deoxyadenosine (CdA) ; omeprazole ; food ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of oral CdA (0.24 mg/kg) was studied in 4 patients (1 with hairy cell leukaemia and 3 with B-cell chronic lymphocytic leukaemia) to determine any effect of food and fasting with and without omeprazole. Food intake did not significantly influence the bioavailability of CdA (42% after food intake vs 46% while fasting) but it did reduce the maximum plasma concentration (Cmax) by 40%; 83 compared to 116 nM while fasting. The time to reach maximum concentration (tmax) was delayed about 0.8 h after food intake. Pretreatment with omeprazole did not significantly influence the bioavailability of CdA (51% vs 46% without), or the interindividual variability in bioavailability in the fasting state (C.V. 0.26 with and C.V. 0.27 without). In conclusion, there was a small, though not statistically significant reduction in the bioavailability of CdA after food intake. Omeprazole did not significantly improve the bioavailability of CdA.
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  • 95
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    European journal of clinical pharmacology 44 (1993), S. 583-586 
    ISSN: 1432-1041
    Keywords: Carvedilol ; Drug interaction ; digitoxin ; phenprocoumon ; pharmacokinetic interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The possibility of a pharmacokinetic interaction between carvedilol and digitoxin (Study I) or phenprocoumon (Study II) has been evaluated in groups of 12 healthy volunteers. The bioavailability (Cmax, tmax, AUC) of digitoxin and phenprocoumon were assessed after a single dose, given once alone and once on day 6 of treatment with carvedilol 25 mg o.d. Cmax, tmax, AUC and Ut of carvedilol and desmethylcarvedilol were also investigated after the fifth dose of carvedilol and after the sixth dose given concomitantly with digitoxin or phenprocoumon. In Study I, the 95% confidence intervals of the ratio test versus the reference findings were; digitoxin Cmax 0.80–1.20, tmax 0.56–1.14, AUC 0.97–1.33, and for carvedilol Cmax 0.81–1.22; tmax 0.66–1.23; AUC 0.91–1.17. Formation of the active metabolite desmethylcarvedilol and the urinary recovery of carvedilol and esmethylcarvedilol were not influenced by digitoxin. In Study II Cmax and AUC of phenprocoumon were not changed after carvedilol. Cmax of carvedilol was decreased after phenprocoumon. The kinetic parameters of phenprocoumon were Cmax 0.80–1.05, tmax 0.47–2.00, AUC 0.78–1.05, and for carvedilol Cmax 0.59–1.06, tmax 0.71–1.73; AUC 0.80–1.08, respectively. The plasma levels of desmethylcarvedilol and the urinary recovery of carvedilol and desmethylcarvedilol were not influenced by phenprocoumon. The blood pressure and heart rate after carvedilol alone were not affected by concomitant administration of digitoxin or phenprocoumon.
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  • 96
    ISSN: 1432-1041
    Keywords: Amitriptyline ; Toloxatone ; Depression ; pharmacokinetics ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The possibility of a pharmacokinetic interaction between amitriptyline and toloxatone (a new MAOI-A) has been studied in 17 depressed in-patients. Amitriptyline and its demethylated and hydroxylated metabolites in blood and urine were measured at steady state after the administration of amitriptyline with and without toloxatone in steady state. The metabolic status of patients was determined using the dextromethorphan phenotyping test. There was only a minor pharmacokinetic interaction between amitriptyline (AMT) and toloxatone, with a small increase in the AMT/NT (nortriptyline) plasma ratio: 0.68 before and 0.78 after toloxatone. The urinary excretion and plasma levels of AMT and its metabolites were not affected by the co-therapy. Three of the patients were poor metabolisers, but this did not predict the magnitude of the drug interaction. The interaction does not justify plasma level monitoring of amitriptyline as the change in pharmacokinetics was so small.
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  • 97
    ISSN: 1432-1041
    Keywords: Felodipine ; Nitrendipine ; Nifedipine ; pharmacokinetics ; stereoselectivity ; enantiomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of racemic (rac) felodipine, rac-nitrendipine and nifedipine (all given as an oral dose of 20 mg in solution) have been investigated in a randomised cross-over study in 12 healthy male subjects using stereoselective assays. Both felodipine and nitrendipine exhibited stereoselective pharmacokinetics. On average, the AUCs of the active (S)-enantiomers of felodipine and nitrendipine were 139% and 104% higher than those of their optical antipodes, but the elimination half-lives of the enantiomers of each racemate were not different. The AUCs of nifedipine, rac-felodipine, rac-nitrendipine and of their enantiomers were highly correlated (all r〉0.83), suggesting closely related rate limiting steps in the in vivo first-pass metabolism of these high-clearance drugs. Stereoselectivity was only a minor contributor to inter-individual variability in the oral pharmacokinetics of these compounds in healthy subjects.
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  • 98
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    European journal of clinical pharmacology 44 (1993), S. 183-187 
    ISSN: 1432-1041
    Keywords: Perindopril ; Haemodialysis ; angiotensin-converting enzyme inhibitors ; perindoprilat ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have studied the pharmacokinetics of perindoprilat, the active metabolite of perindopril, in 7 hypertensive patients undergoing haemodialysis after short-term and long-term (1 month) perindopril. We also measured angiotensin-converting enzyme activity. Each subject took 2 mg of perindopril after a 4-hour haemodialysis. Serial blood samples were obtained each hour during dialysis and between dialysis (7 samples over 44 h). Perindoprilat steady state was reached within 5 haemodialysis sessions. There was a high degree of angiotensin converting enzyme inhibition after the first dose. Administration for 1 month did not modify the time to peak perindoprilat concentration but significantly increased the mean maximal concentration: 10.2 versus 26.8 ng · ml−1. The mean accumulation ratio was 3.5. The mean reduction in perindoprilat concentration after dialysis was greater than 50%. Perindoprilat haemodialysis clearance was 62 ml · min−1 after the first administration and 72 ml · min−1 after 1 month. Tolerance of perindopril was good throughout the study. Treatment can be begun with 2 mg of perindopril after haemodialysis in hypertensive patients undergoing haemodialysis.
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  • 99
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    European journal of clinical pharmacology 44 (1993), S. 225-230 
    ISSN: 1432-1041
    Keywords: Nicotine ; subcutaneous ; pharmacokinetics ; stable isotopes ; deuterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The stable isotope-labeled compound 3',-3'-dideuteronicotine (nicotine-d2) was used to investigate the disposition kinetics and effects of nicotine administered subcutaneously to 6 smokers. Plasma nicotine-d2 concentrations were measured for 8 h after subcutaneous injection of 4 doses (0.4, 0.8, 1.2, and 2.4 mg). Peak plasma nicotine concentration correlated well with the dose, averaging 2.8 to 14.8 ng/ml, 19 to 25 min after injection of the 0.4 mg and 2.4 mg doses, respectively. The plasma clearance over bioavailability ratio (CL/f) averaged 12 to 13 ml · min−1 · kg−1, similar to the clearance reported previously for intravenously administered nicotine. Thus, bioavailability appears to be approximately 100%. The heart rate response was more sensitive to the nicotine dose than the blood pressure response. Subjective effects showed large interindividual variability. The results reported herein may be useful in planning future studies. Administration of nicotine by the subcutaneous route appears to be a practical and safe method for studying the human pharmacology of nicotine.
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  • 100
    ISSN: 1432-1041
    Keywords: Terfenadine metabolism ; cimetidine ; ranitidine ; antihistamines ; Torsades de Pointes ; pharmacokinetics ; drug interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Terfenadine is a widely prescribed non-sedating antihistamine which undergoes rapid and almost complete first pass biotransformation to an active carboxylic acid metabolite. It is unusual to find unmetabolised terfenadine in the plasma of patients taking the drug. Terfenadine in vitro is a potent blocker of the myocardial potassium channel. Overdose, hepatic compromise and the coadministration of ketoconazole and erythromycin result in the accumulation of terfenadine, which is thought to be responsible of QT prolongation and Torsades de Pointes ventricular arrhythmia in susceptible individuals. Cimetidine and ranitidine are two popular H2 antagonists which are often taken with terfenadine. The effects of cimetidine and ranitidine on terfenadine metabolism were studied in two cohorts of 6 normal volunteers given the recommended dose of terfenadine (60 mg every 12 h) for 1 week prior to initiation of cimetidine 600 mg every 12 h or ranitidine 150 mg every 12 h. Pharmacokinetic profiles and morning pre-dose electrocardiograms were obtained whilst the patients were on terfenadine alone and after the addition of cimetidine or rantidine. One of the subjects in each cohort had a detectable plasma level of parent compound after 1 week of terfenadine therapy alone; it did not accumulate further after addition of the H2 antagonist. The pharmacokinetics of the carboxylic acid metabolite of terfenadine (Cmax, tmax, AUC) were not significantly changed after co-administration of either H2 antagonist. None of the remaining 5 subjects in either cohort demonstrated accumulation of unmetabolised terfenadine after addition of the respective H2 antagonist and electrocardiographic QT intervals and T-U morphology in them was not changed during the course of the study. We conclude that cimetidine and ranitidine in the dosages used in this study did not affect the metabolism of terfenadine, and that patients exposed to these drug combinations are not at increased risk of altered cardiac repolarisation.
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