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  • Articles  (333)
  • pharmacokinetics  (182)
  • Rat  (115)
  • Animals
  • Chemical Engineering
  • Saccharomyces cerevisiae
  • Springer  (333)
  • 1975-1979  (333)
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  • Articles  (333)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 27 (1979), S. 161-164 
    ISSN: 1432-0827
    Keywords: Osteoporosis ; Ovary ; Rat ; Vitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Fifty adult female rats were used to study the effect of 1-alpha-hydroxyvitamin D3 (1α-OH-D3)on bone after oophorectomy. The experimental period was 6 months. At the end of the experiment the femurs and the tibias were investigated for bone mass and composition. Significant signs of osteopenia occurred as a result of oophorectomy. The treatment with 1α-OH-D3 induced only minor changes in blood chemistry but increased bone mass significantly. The findings support the view that 1α-OH-D3 may be a valuable tool in the treatment of osteoporosis resulting from ovarian insufficiency.
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  • 2
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    Current genetics 1 (1979), S. 63-74 
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Translation ; Coordinate regulation ; Electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The products of protein synthesis from exponential phase cultures of Saccharomyces cerevisiae grown at 23 °C or at 36 °C appear to be essentially identical. However, yeast cells respond to a shift in culture temperature from 23 °C to 36 °C with the rapid de novo synthesis of a polypeptide species of molecular weight 100,000. Within 60–90 min after the shift this polypeptide represents approximately 2.5% of the total cellular protein, a 5–10 fold increase over the preshift level. The level of this polypeptide then decreases with continued growth of the cells at 36 °C. Analyses by SDS-polyacrylamide gel electrophoresis of polypeptides obtained from cells pulse labeled with [35S]methionine demonstrate that following a temperature shift from 23 °C to 36 °C the synthetic rate of the 100,000 molecular weight polypeptide (as well as a number of other polypeptide species) increases to a level at least 10 fold higher than that observed prior to the shift. A concomittant decrease is observed in the synthesis of a large number of polypeptide species which were actively synthesized before the shift. Maximum changes in synthetic rates are observed 20–30 min after the shift and preshift synthetic patterns are regained within 60–90 min. Synthetic changes of the same magnitude and time course can be produced by short (20–30 min) exposures to 36 °C implicating a heat shock response. Several of the transiently induced polypeptides, including the 100,000 molecular weight species, show an affinity for DNA as determined by DNA-cellulose chromatography.
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  • 3
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    European journal of clinical pharmacology 16 (1979), S. 203-209 
    ISSN: 1432-1041
    Keywords: dantrolene sodium ; spasticity ; twitch tension ; dose response ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Dantrolen sodium is a muscle relaxant, which is used in the treatment of spasticity. Although it is given chronically, little is known about its pharmacokinetic behaviour. The relationship between the effect of a single oral dose of dantrolene sodium and its plasma concentration in healthy volunteers was studied by measuring the effect on the twitch tension, and in spastic patients on the decrease in muscle hypertonia. On the twitch tension dantrolene gave a depression of 49.1±9.4% (±SD) within 1.15 and 3.45 h after ingestion of 100 mg. The mean maximal plasma concentration was 1.24±0.32 µg/ml (±SD). The effect and the plasma concentration were correlated. No relationship between the plasma concentration of dantrolene sodium and its effect could be established in patients, although definite activity in 6 out of 7 patients was observed after a single oral dose of 100 mg, and plasma concentration of dantrolene sodium greater than 0.3 µg/ml were consistently associated with better results than placebo treatment in 6 out of 7 patients.
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  • 4
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    European journal of clinical pharmacology 16 (1979), S. 287-293 
    ISSN: 1432-1041
    Keywords: linear system theory ; perfusion model ; cardiac output ; pulmonary extraction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Assessment of pharmacokinetics in terms of circulatory drug transport is proposed using the methods of linear system theory. In this model-independent approach drug distribution and disposition are characterized by the total extraction ratio, the mean residence time in the body and the volume of distribution at steady state. In analyzing concentration(c)-time(t) data, the procedure requires calculation only of the areas under the c(t)-and c(t)×t-curves to estimate kinetic parameters, and for prediction of the steady state concentration following continuous infusion or multiple doses. Pulmonary clearance of drugs is included in the theory.
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  • 5
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    European journal of clinical pharmacology 15 (1979), S. 275-280 
    ISSN: 1432-1041
    Keywords: Parkinson's disease ; bromocriptine ; pharmacokinetics ; plasma concentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma kinetics of bromocriptine (BCT), a long-acting dopamine agonist, was studied in twelve patients with Parkinson's disease, using a newly developed gas chromatographic method of analysis. Each patient received BCT for at least three weeks in a constant but different dose regimen. Concomitant treatment with 1-DOPA was not allowed. During a 6-day hospitalization period, a blood sample was taken immediately before the afternoon dose at 14.00 h (Cmin) to determine the steady-state level. On the 6th day blood samples were collected every hour during two 8 h dose intervals. The results showed a significant correlation between the mean values of the AUC and the Cmin. First order elimination kinetics appeared to be followed by BCT, at least for the plasma concentrations commonly found. Considerable inter-individual variation was demonstrated both for the dose/plasma concentration ratio and for calculated plasma clearances. No serious side-effects were observed during the investigation.
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  • 6
    ISSN: 1432-1041
    Keywords: indobufen ; platelet aggregation ; food effect on bioavailability ; repeated administration ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of food on bioavailability of indobufen tablets was investigated in 6 healthy volunteers. Subsequently, the same subjects took 100 mg b.i.d. for 7 days. Plasma levels and urinary excretion of indobufen were determined by GLC. Platelet aggregation induced by several concentrations of adrenaline was determined turbidimetrically at various times after the first and last doses. The absorption of indobufen tablets was not substantially impaired by the presence of food in the GI tract, although peak plasma levels and AUCs were slightly reduced after food. Pharmacokinetic analysis of plasma and urinary levels of indobufen did not indicate any change in drug disposition after repeated dosing. Adrenaline-induced platelet aggregation was markedly inhibited for up to 12 h after the first dose and the intensity and duration of this effect did not change after repeated administration. A twice-daily dosing appears suitable for clinical trials.
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  • 7
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    European journal of clinical pharmacology 15 (1979), S. 341-347 
    ISSN: 1432-1041
    Keywords: clofibrate ; chlorophenoxyisobutyric acid ; disposition ; hepatitis ; cirrhosis ; renal failure ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition of clofibrate over 96 hours was observed following single oral dose in six patients with acute viral hepatitis, six patients with liver cirrhosis, seven patients with renal insufficiency, and six control subjects. No parameter of the disposition of CPIB (active form of clofibrate) was significantly altered in acute hepatitis. In liver cirrhosis, the mean plasma half-life was unchanged compared to controls (20.9 vs. 17.5 h), but plasma clearance of the non-protein bound drug was reduced (115 vs. 243 ml×min−1), plasma protein binding was reduced (92.8 vs. 97.2 percent), and the apparent volume of distribution was increased (0.20 vs. 0.141×kg−1). In renal insufficiency plasma half-life was prolonged 2 to 6-fold, depending on the degree of renal impairment. Total plasma clearance (3.4 vs. 7.1 ml×min−1) and plasma clearance of the unbound drug (81 vs. 243 ml×min−1 were reduced in patients with renal failure, the clearance of the unbound drug being inversely correlated with the serum creatinine concentration. Renal failure was also associated with decreased protein binding and an increased volume of distribution of CPIB, and with reduced urinary excretion of CPIB and its glucuronide metabolite. The dose of clofibrate should be halved in patients with cirrhosis. In renal insufficiency, the dose should be adjusted according to the individual serum creatinine level: only 10 to 15% of the usual weekly dose should be given in complete renal failure.
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  • 8
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    European journal of clinical pharmacology 15 (1979), S. 363-366 
    ISSN: 1432-1041
    Keywords: methotrexate ; protein binding ; ultrafiltration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The protein binding of methotrexate by serum from eight normal volunteers was assessed by continuous ultrafiltration at pH 7.4 and 37°C. Methotrexate concentrations were measured by radioimmunoassay and the data analysed by the method of Scatchard. The major binding protein was albumin which bound 87.3% of the drug in serum. Analysis of the Scatchard plots indicated two distinct groups of binding sites. Class I was found to have 0.16±0.05 (S D) binding sites with an intrinsic association constant of 71.15±35.98 (S D)×104 M−1: Class II had 2.01±0.93 (S D) binding sites and an affinity of 0.18±0.15×104 M−1. No great change in the percentage of methotrexate bound occurred until the total concentration of the drug exceeded 50 µMol 1−1.
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  • 9
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    European journal of clinical pharmacology 16 (1979), S. 243-249 
    ISSN: 1432-1041
    Keywords: timolol ; beta blockade ; pharmacokinetics ; pharmcodynamics ; acute administration ; chronic administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and effects of various oral doses of timolol administered either acutely or after chronic medication for 7 days were studied in healthy volunteers. After acute administration of timolol maximum plasma concentrations were attained within 1–2 h and thereafter declined exponentially with time. The mean apparent half-life of elimination from plasma was 2.5 h and was independent of dose. Area under the plasma concentration-time curve (AUC) was proportional to the orally administered dose. Plasma concentrations, apparent elimination half-life and AUC were not altered after one week of chronic administration. The effect of timolol on heart rate and blood pressure response to three sequentially increasing ‘steady state’ work loads were studied. After acute administration of timolol maximum reduction of systolic blood pressure, resting heart rate, and the different parameters of the work-heart rate (or blood pressure) relationships were produced by 5 mg timolol. Increasing the dose prolonged the duration over which these variables were reduced. The relationship between timolol plasma concentration and inhibition of different parameters of the exercise response was hyperbolic with half maximum inhibition at concentrations of about 3–4 ng/ml of timolol and maximum inhibition above 30 ng/ml. Maximum drug effects and duration of action of timolol on the different variables were similar after acute and chronic administration.
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  • 10
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    European journal of clinical pharmacology 16 (1979), S. 263-270 
    ISSN: 1432-1041
    Keywords: diazepam ; alcoholic beverages ; plasma level ; pharmacokinetics ; co-ordination skills ; red wine ; white wine ; whisky
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twenty paid healthy students ingested diazepam 10 mg 30 min after the administration of ethanol 0.8 g/kg. The alcoholic beverage used was varied in randomized double-blind experiments, which were repeated at one-month intervals. Psychomotor performance, plasma diazepam, and alcohol concentration in breath were measured 30, 60, 90 min and 2, 3, 4, 6 and 24 h after the ingestion of diazepam. Beer and white wine elevated the plasma level of diazepam and the effect lasted for up to 2 h. Whisky elevated the diazepam level for 90 min. Red wine did not affect it significantly. The alcohol-diazepam combination impaired tracking skills and oculomotor co-ordination and enhanced nystagmus, more than diazepam alone. Red wine produced a breath alcohol concentration higher than after white wine. More nystagmus was recorded after red wine and diazepam, although white wine led to a higher plasma diazepam concentration. It appears that simultaneous ingestion of alcohol and diazepam accelerates the absorption of diazepam. This pharmacokinetic alteration may not contribute much to the combined psychomotor effects of diazepam and alcohol, which were mainly due to pharmacodynamic interaction at receptor level.
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  • 11
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    European journal of clinical pharmacology 16 (1979), S. 271-277 
    ISSN: 1432-1041
    Keywords: lithium ; litarex ; single dose ; multiple dose ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary An analysis of the single and multiple dose pharmacokinetics of lithium in 7 healthy volunteers is presented. A solution of lithium chloride was administered in single dose experiments and the same solution and a sustained release preparation were employed in multiple dose experiments, which were carried out at steady state. A fixed dose of 24 mmol was used in the single dose experiments and in the subsequent multiple dose experiments in the same subjects the same dose was administered once daily for a week. Distinct two-compartment characteristics were found, with a mean disposition rate constant (β) of 0.035 h−1±0.010 SD, corresponding to a mean biological half-life of about 19.8 h. The mean half-time of the distributory α-phase was about 1.15 h. The absorption of lithium from an orally administered solution took place with a half-time of about 0.15 h in the single dose experiments. The apparent volume of distribution of the central compartment (Vc) was 0.307 1 kg−1±0.046 SD, less than half that of Vde at equilibrium. Vdβ (Vdarea) was 0.8291 kg−1±0.184 SD and mean total body clearance was 27.6 ml kg−1 h−1±4.7 SD.
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  • 12
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    European journal of clinical pharmacology 16 (1979), S. 255-262 
    ISSN: 1432-1041
    Keywords: spironolactone ; canrenone ; fluorimetry ; high performance liquid chromatography ; linear kinetics ; saturation kinetics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In Study I 20 normal volunteers received a single oral dose of spironolactone 100 mg. In Study II a further 20 normal volunteers were given first spironolactone 100 mg b.i.d. and subsequently spironolactone 100 mg once a day for a further 4 days. In Study III 5 normal subjects were given a single dose of spironolactone 500 mg. The concentration of canrenone in serum was determined both by fluorimetry and HPLC for 0–48 h in Study I, 120–168 h in Study II and 0–36 h in Study III. The total AUCs after the single 100 mg dose did not differ from the AUCs within the dosing interval during steady state. The half-lives of the terminal log-linear phases were almost identical (14.99±0.80 h and 15.69±0,80 h) when determined by fluorimetry, and were sligthly, but significantly (p〈0.01), longer when determined by HPLC — 20.14±1.62 and 18.71±1.04. The mean ratio of the specific AUC determined by HPLC and the fluorimetrically determined AUC was 0.3 after the single 100 mg dose. It did not differ from the corresponding value during steady state (0.34). In contrast, the ratio after the single 500 mg dose was approximately 50% higher. Fluorimetrically determined AUCs after 100 and 500 mg doses did not show dose-proportionality in contrast to the HPLC-determined AUCs. It was concluded that Canrenone contributes much less to the conventional fluorimetric determination than was previously assumed. It may not provide more than 1/10 and 1/4 of the antimineralocorticoid activity of spironolactone after single dose and multiple doses, respectively. Whereas linear kinetics apply after single and multiple 100 mg doses of spironolactone, after 500 mg saturation kinetics must be assumed with respect to metabolism. Thus, in bioavailability studies high doses of spironolactone should be avoided. For such studies the fluorimetric assay seems to be the appropriate bioanalytical method in spite of its lower specificity.
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  • 13
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    European journal of clinical pharmacology 15 (1979), S. 187-192 
    ISSN: 1432-1041
    Keywords: quinidine ; plasma protein binding ; pharmacokinetics ; man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition and plasma protein binding of quinidine after intravenous administration were studied in 13 healthy subjects. Plasma protein binding, expressed as the fraction of quinidine unbound ranged from 0.134–0.303 (mean 0.221). Elimination rate constant (β) varied from 0.071 to 0.146 h−1 (mean 0.113), and apparent volume of distribution (Vβ) varied from 1.39–3.20 l · kg−1β (mean 2.27). Total body clearance was 2.32–6.49 ml min−1 · kg−1. There was a positive linear correlation between the plasma fraction of unbound quinidine and both Vβ (r=0.885, p〈0.01) and total body clearance (r=0.668, p〈0.05). No significant correlation existed between the fraction of unbound quinidine in plasma and the elimination rate constant. The results show that both the apparent volume of distribution and total body clearance of quinidine are proportional to the unbound fraction in plasma. This implies that the total plasma concentration of quinidine at steady state will change with alterations in plasma binding, whilst the concentration of unbound compund and its elimination rate will remain unaffected.
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  • 14
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    European journal of clinical pharmacology 15 (1979), S. 153-157 
    ISSN: 1432-1041
    Keywords: cimetidine ; renal failure ; elimination half life ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma concentration curve after a single oral dose of cimetidine 200 mg was followed in 27 patients with varying degrees of chronic renal failure (creatinine clearance 1–52 ml/min) and in 46 patients with normal serum creatinine. Compared to the latter patients, the plasma concentration was higher and the elimination rate was slower in all uraemic subjects, including a group with moderate renal impairment. The preliminary recommendations of dosage for patients with a creatinine clearance below 5 ml/min, and for patients on regular haemodialysis, is cimetidine 200 mg every 12 h, 5–15 ml/min 200 mg every 12 to 8 h, 15–30 ml/min 200 mg every 8 h and 30–52 ml/min 200 mg every 6 h.
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  • 15
    ISSN: 1432-1041
    Keywords: nitrazepam ; epilepsy ; age ; disease ; plasma concentration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of nitrazepam were measured by gas-liquid chromatography in: young healthy volunteers, in geriatric and psychiatric patients and in epileptic children. The disposition of nitrazepam was described in terms of a two-compartment open model. After a single oral dose of nitrazepam 5 mg the most prominent differences between the experimental groups were in the β-phase half-life-mean 29 h in the young volunteers and 40 h in geriatric patients, and in the apparent volume of distribution during the β-phase of 2.4 vs 4.8 l/kg. Total plasma clearance and the average steady state concentration in both groups were equal. The plasma level rose at a rate proportional to the β-phase half-life, and so, they were achieved more rapidly in the young than in the old subjects (3.5 vs 7.5 d). No change in steady-state level or in the half-life of nitrazepam were found during long term treatment, which indicates lack of enzyme induction or inhibition. In 95% of the epileptic children with a good to fair clinical response, the plasma concentration of nitrazepam was 40–180 ng/ml (mean 114 ng/ml). As all of the patients were on combined antiepileptic therapy, no attempt was made to correlate plasma level with therapeutic response.
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  • 16
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    European journal of clinical pharmacology 15 (1979), S. 175-180 
    ISSN: 1432-1041
    Keywords: clorazepate ; nordiazepam ; pregnancy ; pharmacokinetics ; intramuscular injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A single dose of clorazepate 20 mg was injected i.m. in 7 pregnant and 7 non-pregnant women. Blood samples were collected for one week, and urine was collected for 24 h after the dose. The concentrations of clorazepate and its metabolite nordiazepam were determined by electron capture gas liquid chromatography. There was no difference between the two groups on physical examinations. Clorazepate was rapidly absorbed and the peak concentration was reached within 2h. Mean pharmacokinetic parameters for clorazepate were absorption half life 0.77h in pregnant women and 0.56h in non-pregnant women; elimination half life 1.3h in pregnant women and 2.0h in non-pregnant women; volume of distribution: 0.43 l · kg−1 in the pregnant women and 0.33 l · kg−1 in non-pregnant women. Nordiazepam reached its peak concentration within 12h after dosing; its mean half life of elimination was 180h in pregnant women and 60h in non-pregnant women. Within 24h, 1.3% of the clorazepate was recovered in urine from pregnant women and 7% in urine from the non-pregnant women.
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  • 17
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    European journal of clinical pharmacology 15 (1979), S. 257-261 
    ISSN: 1432-1041
    Keywords: cimetidine ; H2-receptor antagonist ; aging ; single dose ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The blood level versus time curve for unchanged cimetidine after a 200 mg oral dose has been determined in 20 apparently healthy subjects, ranging from 22 to 84 years of age. A significant relationship between the area under the curve (AUC) and age was found (r=0.81; P〈0.001). The peak concentrations of cimetidine were significantly inversely related to body weight (r=−0.71; P〈0.001). The age-related increase in bioavailability of oral cimetidine, as measured by AUC, was probably due to decreased total clearance of the drug, which resulted from the opposed changes (by themselves not significant) of distribution volume towards a decrease and of half-life towards an increase with age. Reduction in the standard oral dose of cimetidine by one third to one half should be feasible in the elderly without loss of efficacy, and it may be advisable in order to obviate extreme individual responses that may occur in this population.
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  • 18
    ISSN: 1432-1041
    Keywords: chlorthalidone ; pharmacokinetics ; oral and i.v. doses ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Seven normal human volunteers each received a constant-rate infusion of chlorthalidone for 2 h, and the same (commonly 50 mg) single oral dose on separate occasions. The concentration of unchanged chlorthalidone was analyzed over a 100 to 220 h period in plasma, red blood cells, urine and faeces after both dosage forms. A three compartment model was required to describe the intravenous plasma concentrations in five of the subjects. A two compartment model sufficed to account for the decay of the oral plasma concentrations in all seven subjects. The mean plasma t1/2 after i.v. dosing was 36.5 h (±10.5 SD), and the mean plasma t1/2 after oral doses was 44.1 h (±9.6 SD). The mean red blood cell concentration t1/2 after i.v. doses was 46.4 h (±9.9 SD), and the mean red blood cell t1/2 after the oral doses was 52.7 h (±9.0 SD). The shorter i.v. half-live was not equally manifest in all subjects, being mainly apparent in three of them. In all cases the urinary excretion rate plots were parallel to the plasma concentration curves. As the faster decay after i.v. administration was not accompanied by increased renal clearance, the difference must have been due to non-renal mechanism. The mean total of 65.4 (±8.6 SD) % of the intravenous dose was excreted in urine over infinite time, whereas the mean total excretion after the oral dose was 43.8 (±8.5 SD) %. Faecal excretion ranged from 1.3–8.5% of dose in the i.v. study to 17.5–31.2% of dose in the oral study. The sum of the amounts present in urine plus faeces pointed strongly to an important metabolic route of elimination of chlorthalidone. Bioavailability estimates (F) from three sets of data were — a mean F of 0.61 from plasma concentrations, 0.67 from urinary excretion measurements and 0.72 from the erythrocyte concentrations. Simulations with a non-linear model indicated lesser validity of the estimate from erythrocyte concentrations. It was concluded that the average of plasma and urine data, F=0.64, yielded the best estimate of the oral availability of chlorthalidone 50 mg in man.
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  • 19
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    European journal of clinical pharmacology 15 (1979), S. 121-125 
    ISSN: 1432-1041
    Keywords: guanethidine ; chronic therapy ; urinary excretion ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma level and urinary excretion rate of guanethidine have been measured in 30 patients during oral maintenance therapy, and in 5 patients following discontinuation of therapy. A significant correlation was found between the daily average urinary excretion and the maintenance dose, although wide interindividual variation was noted among patients maintained on the same dose. A statistically significant correlation was also observed between the area under the plasma level curve during the dose interval and the oral maintenance dose. After discontinuation of chronic therapy, the half-life of 1.5 days of the initial phase of elimination was essentially in agreement with the half-life of almost 2 days determined in acute studies. In addition, a second phase of elimination with a half-life of 4 to 8 days was observed.
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  • 20
    ISSN: 1432-1041
    Keywords: clorazepate ; nordiazepam ; pregnancy ; placental transfer ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Clorazepate 20mg was given i. m. to 49 mothers during the first stage of labour. The elimination of the drug was studied in 27 newborns produced by these mothers. The same dose was given to 13 women who underwent amniocentesis and to 7 women who were breast-feeding. “Total nordiazepam”, i.e. the sum of clorazepate and its metabolite nordiazepam, was determined by gas-liquid chromatography in maternal blood, umbilical cord blood (both arterial and venous), amniotic fluid and in milk. Clorazepate was found to cross the placental barrier slowly, but nordiazepam was transferred more rapidly. Nordiazepam was found in the milk and in the blood of neonates after breast-feeding had started.
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  • 21
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    European journal of clinical pharmacology 16 (1979), S. 31-38 
    ISSN: 1432-1041
    Keywords: bezafibrate ; hyperlipoproteinemia ; bioavailability ; pharmacokinetics ; GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disposition kinetics of bezafibrate, a newly developed drug of great lipid-lowering potency, were investigated in normal male subjects. Five male volunteers received14C-labelled bezafibrate orally in solution, and a further 10 were given the same dose (300 mg) of un-labelled drug as tablets. The concentration of bezafibrate in serum and urine from the latter was determined by GC, and in the former total radioactivity in serum, urine and feces was followed for 48 h, and urinary excretion products were analysed by TLC and GC-MS. Rapid absorption from the gastrointestinal tract led to peak serum levels 30 min and 2 h after administration of solution and tablets, respectively. Since approximately 95% of the administered14C-bezafibrate was excreted in urine within 48 h, and almost all the remainder was detected in feces, absorption can be regarded as complete after administration in solution. The relative optimal bioavailability from the tablets was also complete, since in both cases approximately 50% of the administered dose was detected as unchanged bezafibrate in urine within 24 h by GC in the tablet study, and by TLC in the solution study. Of the decomposition products, more than 20% of the dose was present as glucuronides and the remainder consisted of several more polar compounds, one of which was identified as a hydroxyderivative of bezafibrate. Since the apparent halflife of bezafibrate in serum was 2.1 h, this new drug possesses favourable pharmacokinetic features: rapid and complete absorption, even from tablets, combined with a conveniently short half-life, and clearance which is half renal (56 ml/min) and half metabolic (43 ml/min), giving a total clearance of 99 ml/min.
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  • 22
    ISSN: 1432-1041
    Keywords: indobufen ; platelet aggregation ; single dose ; bioavailability ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy volunteers received single iv and oral doses of 2-[p-(1-oxo-2-isoindolinyl)phenyl] butyric acid 100 mg (indobufen; K 3920), an inhibitor of platelet aggregation. Plasma levels and urinary excretion of the drug were determined by GLC. Collagen-induced platelet aggregation was assessed turbidimetrically at various intervals after administration. The plasma half-life of the drug was 7–8 h and more than 70% of the administered dose was recovered within 48 h in urine, as unchanged drug and as the glucuronide of indobufen. After oral administration of tablets of two different formulations, the drug was completely absorbed, but one formulation showed faster absorption. The maximal inhibitory effect on platelet aggregation was observed 1 to 4 h after iv administration, and it had decreased by 8 h. After tablets, peak effect and the time of the peak were similar, but activity was significantly prolonged, in accordance with the higher plasma levels found at 8 h. The data suggest that the effect of indobufen on platelets is reversible, and that for this drug platelets behave as a compartment that slowly equilibrates with plasma.
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  • 23
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    European journal of clinical pharmacology 15 (1979), S. 433-441 
    ISSN: 1432-1041
    Keywords: cyclobarbital ; barbiturates ; pharmacokinetics ; drug interaction ; volunteers ; patients
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The disappearance of cyclobarbital from plasma has been followed in healthy volunteers and in neurological and psychiatric patients after oral administration of one tablet of Phanodorm®, containing cyclobarbital calcium 200 mg. Plasma levels were measured by a thin-layer chromatographic method with in situ densitometry. The average t1/2 in healthy female and male volunteers was 13.3 h, and with the assumption of complete availability a mean distribution coefficient of 0.69 l/kg−1 and a clearance of 40.4 ml/min−1 were calculated. Repeated experiments in seven volunteers revealed good reproducibility of all values. When the healthy volunteers were combined with a group of untreated epileptics, a dependence of t1/2 and of the apparent volume of distribution on age was found, while clearance did not change with increasing age (range 17–54 years). Long half-lives caused by low clearance values were observed in several individuals with moderate obesity. No consistent change in cyclobarbital kinetics followed acute exposure of volunteers to alcohol or on treatment of neurological patients with carbamazepine. Patients under treatment with perazine exhibited more or less normal kinetic values. In terms of drug interaction, cyclobarbital differs from phenazone in several respects, and so it may prove a useful additional substance for measurement of the rate of drug oxidation in humans.
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  • 24
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    European journal of clinical pharmacology 16 (1979), S. 1-6 
    ISSN: 1432-1041
    Keywords: lorcainide ; ventricular premature beats ; plasma levels ; pharmacokinetics ; side effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma level and antiarrhythmic effect of lorcainide (R 15889) have been investigated in 15 patients with ventricular premature beats (VPB). Therapy was initiated with an intravenous dose of 1.9 mg/kg given over 10 min, followed by a constant infusion of 0.18 mg/kg/h for 24 h. In 8 patients the corresponding doses were increased to 2 mg/kg and 0.27 mg/kg/h. After the intravenous doses patients were treated orally with 100 mg tid for 6–7 days. The two dosage regimens were selected so as to achieve theoretical steady-state plasma levels (css) of 200 and 300 ng/ml, respectively. The combined intravenous treatment approached (181 ± 6.8 ng/ml and 273±28.5 ng/ml, respectively) the desired css within 2 to 4 h. During the oral administration, the minimal plasma concentrations following the lower intravenous dose (184±18 ng/ml) were significantly (p=0.0001) lower than after the higher intravenous dose (264±20.5 ng/ml). The dealkylated metabolite of lorcainide was not detectable after the intravenous doses, but it accumulated during oral treatment, when its concentration exceeded that of the parent compound. In 5 of the 7 patients receiving the lower dose VPB were effectively reduced. However, in only 4 of the 8 patients on the higher dosage schedule could a significant antiarrhythmic effect be demonstrated. In addition, side effects were observed in 6 of the subjects.
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  • 25
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    European journal of clinical pharmacology 16 (1979), S. 23-29 
    ISSN: 1432-1041
    Keywords: valproate ; epilepsy ; pharmacokinetics ; drug interaction
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In four refractory epileptic patients, peak plasma levels of sodium valproate occurred within 1.5 to 3 h after a single oral dose of valproate and the decline in plasma levels followed a monoexponential course with a t1/2 of 11.4 ± 0.1 h. The mean value for apparent volume of distribution was 0.176 ± 0.013 l/kg and for total plasma clearance 0.0106 ± 0.0009 l/h/kg. Steady state plasma levels were predicted using the method of superposition utilizing pharmacokinetic parameters determined following a single dose of valproate and were 78–123% of the predicted values for two patients receiving valproate alone, and 37–64% of the predicted values for the two patients receiving carbamazepine in addition to valproate. In a further group of 20 patients the mean daily doses of valproate for 8 patients receiving valproate alone (25.4 ± 4.9 mg/kg) was significantly less than those for the 12 patients receiving concomitant anticonvulsant therapy (41.6 ± 12.3 mg/kg) (p〈0.005). In addition, the steady state predose plasma levels of valproate were significantly higher in the valproate alone patients (90.3 ± 8.7 µg/ml) compared to the patients receiving additional anticonvulsants (75.3 ± 13.8 µg/ml) (p〈0.01). The higher dose requirements of valproate and lower predose and steady state plasma levels for those patients on multiple anticonvulsants indicate an interaction between valproate and other anticonvulsants.
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  • 26
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    European journal of clinical pharmacology 16 (1979), S. 45-48 
    ISSN: 1432-1041
    Keywords: quinidine ; slow release formulation ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability of quinidine in two sustained release preparations A and B has been compared in three females and three males with i.v. administration of quinidine. The initial rate of oral absorption did not differ between the two drug preparations; the peak concentration was observed after 4 h both for A and B, but was significantly higher after B. A slower decrease in plasma concentration was observed after preparation A than B. Absolute bioavailability did not differ significantly between A (median value 78.4%) and B (median 87.1%). Drug absorption in vivo was in good agreement with the results of in vitro dissolution tests on both preparations. The slower decrease in plasma concentration found for the new sustained release form of quinidine should be of clinical advantage.
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  • 27
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    European journal of clinical pharmacology 16 (1979), S. 49-52 
    ISSN: 1432-1041
    Keywords: cephacetrile ; haemodialysis ; pharmacokinetics ; renal failure
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of cephacetrile were studied after its administration as a single i.v. bolus injection of 15 mg/kg body weight to 11 patients with terminal renal inpairment undergoing haemodialysis for 6 h. A two-compartment kinetic model was used to describe the biphasic decrease in plasma concentration. The quantities of antibiotic in the central and peripheral compartments, and the amounts eliminated, were calculated for different times. During haemodialysis sessions, the average pharmacokinetic parameters of cephacetrile determined at the dialyser input were: α=5.03 h−1,β=0.458 h−1, K12=2.337 h−1, K21=1.996 h−1 K13=1.154 h−1, Vc=5.508 l, Vp=6.448 l, Vdss=11.956 l. As a function of the pharmacokinetic parameters of cephacetrile, a regimen of multiple doses was established for patients with terminal renal impairment, which will guarantee safe and effective concentrations of the antibiotic.
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  • 28
    ISSN: 1432-1041
    Keywords: methadone ; mass fragmentography ; pulse labeling ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A technique is presented for study of steady state kinetics of methadone using pulse labeling with deuterated methadone (d3) and mass fragmentography to measure both unlabeled and labeled methadone in blood. Seven subjects maintained on methadone for at least 10 months were admitted to a closed metabolic ward. The daily dose of unlabeled methadone (d0) was substituted by one dose of methadone-d3 and plasma levels of methadone-d0 and methadone-d3 were followed for 48 h using a precise (SD±5%) and sensitive (30 pmol/ml) mass fragmentographic technique. Plasma half-lives (t1/2) for both methadone-d0 and metadone-d3 were calculated from samples obtained 8–24 h following the dose of methadone-d3. The t1/2 of oral methadone-d3 was shorter (22±2 h) than that of methadone-d0 (52±20 h). The same pattern was observed after intravenous administration. The results indicate multiple pools of methadone in the body.
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  • 29
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    European journal of clinical pharmacology 16 (1979), S. 177-181 
    ISSN: 1432-1041
    Keywords: prazosin ; alpha receptor blockade ; blood pressure ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and effects of prazosin have been studied after intravenous and oral dosing (1 mg) to 6 normal male volunteers. The mean terminal (β) half-life was 2.9 h after intravenous and oral routes. Oral bioavailability was 56.9%. The effects of prazosin on blood pressure were more pronounced after intravenous than oral administration, and the hypotensive effect greater on erect blood pressure. There was a significant correlation (P〈0.02) between the fall in blood pressure and the plasma drug concentration after intravenous prazosin.
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  • 30
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    European journal of clinical pharmacology 16 (1979), S. 189-194 
    ISSN: 1432-1041
    Keywords: sparteine ; pharmacogenetic defect ; defective metabolism ; pharmacokinetics ; renal excretion
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Sparteine is metabolized by N1-oxidation, which in some subjects is defective. The defect has a pronounced effect on the kinetics of the drug. In non-metabolisers elimination of sparteine proceeds entirely via renal excretion by a capacity-limited process, 99,9% of the dose being excreted as unchanged drug. In metabolisers the drug is mainly eliminated by metabolic degradation. Pronounced differences in β-phase half-life and total plasma clearance were observed between metabolisers (156 min; 535 ml · min−1) and nonmetabolisers (409 min; 180 ml · min−1).
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  • 31
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    European journal of clinical pharmacology 16 (1979), S. 195-202 
    ISSN: 1432-1041
    Keywords: metformin ; biguanides ; pharmacokinetics ; absorption
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetics of14C-metformin have been studied in five healthy subjects after oral and intravenous administration. The intravenous dose was distributed to a small central compartment of 9.9±1.61 ( $$\bar X$$ ±SE), from which its elimination could be described using three-compartment open model. The elimination half-life from plasma was 1.7±0.1 h. Urinary excretion data revealed a quantitatively minor terminal elimination phase with a half-life of 8.9±0.7 h. After the intravenous dose, metformin was completely excreted unchanged in urine with a renal clearance of 454±47 ml/min. Metformin was not bound to plasma proteins. The concentration of metformin in saliva was considerably lower than in plasma and declined more slowly. The bioavailability of metformin tablets averaged 50–60%. The rate of absorption was slower than that of elimination, which resulted in a plasma concentration profile of “flip-flop” type for oral metformin.
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  • 32
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    European journal of clinical pharmacology 16 (1979), S. 327-330 
    ISSN: 1432-1041
    Keywords: atenolol ; food intake ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the bioavailability of the beta-adrenoceptor blocker atenolol was assessed by measurement of its single-dose kinetics in ten healthy volunteers, who took 100 mg both in the fasting state and together with a standardized breakfast. Food intake significantly shortened the time to reach peak concentration (2.7 h vs 1.5 h), but caused a significant reduction in AUC values, the mean decrease being 20%. The elimination half-life was unaffected. Atenolol, which is relatively hydrophilic, is incompletely absorbed in the fasting state, and escapes first-pass metabolism. The present findings indicate that food intake causes further impairment of its absorption, even though the absorption rate may initially be enhanced. This contrasts with previous observations on the more lipophilic beta-adrenoceptor blockers propranolol and metoprolol.
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  • 33
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    European journal of clinical pharmacology 16 (1979), S. 331-334 
    ISSN: 1432-1041
    Keywords: netilmicin ; radioenzymatic assay ; drug accumulation ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a single dose of netilmicin (NM) was studied in 6 healthy volunteers. Elimination of the drug was followed in serum and urine for 24 h and 72 h, respectively. NM concentrations were measured with a modified radioenzymatic assay. A three compartment open model was employed to calculate the pharmacokinetic parameters. Following the rapid initial distribution, biphasic elimination with half lives of 1.99 h (t1/2β) and 36.89 h (t1/2γ) was demonstrated. Measurable amounts of NM were excreted in the urine for up to 72 h. The volume of distribution at steady-state (Vdss) of 0.68 l/kg was 3 to 4 times larger than previously reported for this antibiotic. NM plasma clearance was 91 ml/min and the renal clearance was 67 ml/min. The data indicate that on repetitive dosing the amount of drug in the body would be considerably underestimated if the prolonged terminal elimination phase were not taken into account. During prolonged treatment, accumulation of NM in renal and other tissues is likely to occur, as has been described for other aminoglycosides. The possible consequences of this pharmacokinetic behaviour are discussed.
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  • 34
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    European journal of clinical pharmacology 16 (1979), S. 335-340 
    ISSN: 1432-1041
    Keywords: cimetidine ; enterohepatic circulation ; irregular absorption ; bioavailability ; pharmacokinetics ; volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The bioavailability and pharmacokinetics of cimetidine have been studied in healthy volunteers after administration of single intravenous (100 mg) and oral doses (100, 400 and 800 mg). After i.v. administration, the kinetics of cimetidine could be described by a linear, two compartment open model. Substantial variation in half-life was observed between subjects, with a mean value of 2.1 h (range 0.9–4.7). Cimetidine had a low hepatic extraction ratio and a high total plasma clearance, due to extensive urinary excretion of unchanged drug. After oral administration, the plasma concentration vs time curves in most subjects exhibited two marked peaks, an observation that seemed to be constant within individuals and was independent of dose. Bioavailability, estimated as the area under the plasma concentration vs time curves (AUC), after oral doses as compared to the intravenous dose, in most cases exceeded 100%. There was no correlation between bioavailability estimated as AUC and as urinary excretion of unchanged drug. These observations may indicate an enterohepatic circulatory mechanism, predominantly after oral administration. Both unchanged drug and its sulphoxide metabolite appear to be excreted in bile. The latter was shown in vitro to be reduced to cimetidine by fecal bacteria.
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  • 35
    ISSN: 1432-1041
    Keywords: prenalterol ; metoprolol ; haemodynamics ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The haemodynamic effects of the selectiveβ 1-adrenoceptor agonist prenalterol were studied in healthy subjects before and after therapeutic doses of the selectiveβ 1-adrenoceptor blocker metoprolol. Plasma levels of the drugs were also determined in order to calculate certain pharmacokinetic variables. Intravenous infusion of prenalterol 0.13, 0.25 and 0.50 mg induced a dose-dependent decrease in total electromechanical systole (QA2) and pre-ejection period (PEP). The effect on left ventricular ejection time (LVET) was not significant. Increases in systolic blood pressure and heart rate were dose-dependent. Diastolic blood pressure did not change significantly. When metoprolol had been administered in a cumulative dose of 150 mg (mean maximal plasma level, 284 nmol/1) prenalterol had to be administered in doses that were twelve times higher than before theβ-blocker in order to induce the same haemodynamic effects. Prenalterol was rapidly distributed with an average half life of 8 min. This indicates that distribution equilibrium will be achieved within 30 min after intravenous administration. The overall elimination rate in the post-distributive phase corresponded to an average half life of 2.0 h.
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  • 36
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    European journal of clinical pharmacology 15 (1979), S. 269-274 
    ISSN: 1432-1041
    Keywords: phenytoin ; food-intake ; bioavailability ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The influence of food intake on the absorption of phenytoin was examined in eight healthy volunteers, by study of single-dose kinetics following ingestion of phenytoin 300 mg either with a standardized breakfast or on an empty stomach. Blood samples were collected at regular intervals from 0 to 48 h, and serum concentrations of unmetabolized phenytoin were determined by gas chromatography. Serum concentrations of the major metabolite of phenytoin, 4-hydroxyphenytoin, were measured by mass fragmentography. Concurrent intake of food and phenytoin appeared to accelerate absorption of the drug from the formulation used, and the peak concentrations were significantly higher (mean increase 40%) in the postprandial than in the preprandial state. As reflected by the AUC (area under the curve), the amount of drug absorbed was increased during postprandial conditions, although the difference only reached borderline significance. It is suggested that phenytoin should always be taken in a defined relation to meals.
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  • 37
    ISSN: 1432-1041
    Keywords: myasthenia gravis ; neostigmine ; gas chromatography-mass spectrometry ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary To permit rational evaluation of the empirical pharmacotherapy of myasthenia with cholinesterase inhibitors, a sensitive and selective method for the determination of neostigmine has been developed. Analysis is based on ion-pair extraction of neostigmine into methylene chloride and determination by gas chromatography-mass spectrometry (chemical ionization). As neostigmine was found to be metabolized in plasma in vitro, deuterated (d6) neostigmine was immediately added to the plasma sample as the internal standard. The limit of quantitation of the method was about 1 ng/ml (∼ 3nmol/l). The kinetics following i. v. administration were studied in four patients, who received neostigmine 2.5–3.0 mg iv to antagonize pancurone administered during anaesthesia. Elimination was rapid with a half-life t1/2 (β-slope) of 0.89±0.05 h (mean ± SE). The volume of distribution was 1.08±0.11 l/kg and plasma clearance was 0.84±0.04 l/kg/h. In three fasting myasthenic patients plasma concentrations of neostigmine were followed for 5 h after a single oral dose of 30 mg. Considerable interindividual differences in absorption were expressed in the peak concentrations, which occurred 1–2 h following drug ingestion. The bioavailability of neostigmine was estimated to be 1–2% of the ingested dose. Neostigmine concentration in plasma was found to differ considerably (up to forty-fold) between myasthenic patients on their ordinary dose-schedules of cholinesterase inhibitors.
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  • 38
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    European journal of clinical pharmacology 16 (1979), S. 101-105 
    ISSN: 1432-1041
    Keywords: dihydroquinidine ; congestive heart failure ; intravenous administration ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of dihydroquinidine were studied in 8 patients with congestive heart failure following a 22 min intravenous infusion of a quinidine preparation that contained 5.9% dihydroquinidine as an impurity. Using a thin layer chromatography-fluorometric assay procedure for dihydroquinidine, the post-infusion plasma dihydroquinidine concentrations declined biexponentially. The half-life of the fast and slow dispositional processes was 4.42±1.81 min and 6.52±2.40 h, respectively. The central compartment volume for dihydroquinidine in these patients was 0.44±0.11 l/kg with an overall apparent volume of distribution of 1.14±0.38 l/kg. The computed values of total body plasma clearance of dihydroquinidine ranged from 1.29 to 2.69 ml/min/kg with a mean value of 1.94±0.60 ml/min/kg. In these patients, approximately 16% of the administered dihydroquinidine dose was excreted intact into the urine in 48 h. The estimated value of renal clearance was 0.314±0.129 ml/min/kg. When compared to control cardiac patients, the data showed that the apparent volume of distribution for dihydroquinidine is smaller in patients with congestive heart failure and as a result of this diminished volume, the clearance rate of dihydroquinidine was slower. The net effect of these differences was the production of higher plasma concentrations of dihydroquinidine in the heart failure group.
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  • 39
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    European journal of clinical pharmacology 16 (1979), S. 119-124 
    ISSN: 1432-1041
    Keywords: cefoxitin ; renal impairment ; pharmacokinetics
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of cefoxitin have been determined after a single i.v. injection of 15 mg/kg body weight in 10 patients with normal renal function and 20 patients with varying degrees of renal impairment. The kinetics of the antibiotic followed an open two-compartment model. In patients with normal renal function the following pharmacokinetic parameters were found: $$\begin{gathered} \begin{array}{*{20}c} {\alpha = 8.66 h^{ - 1} } & {\beta = 1.21 h^{ - 1} } & {K_{12} = 3.47 h^{ - 1} } \\ \end{array} \hfill \\ \begin{array}{*{20}c} {K_{21} = 3.17 h^{ - 1} } & {K_{13} = 3.15 h^{ - 1} } & {V_c = 4.24 l.} \\ \end{array} \hfill \\ \begin{array}{*{20}c} {V_p = 4.87 l.} & { Vd_{ss} = 9.11 l.} \\ \end{array} \hfill \\ \end{gathered}$$ In the patients with renal impairment there was a significant decrease in $$\mathop \alpha \limits_, \mathop \beta \limits_, $$ K12, K21 and K13, and an increase in the apparent volume of distribution. The degree of plasma protein binding in patients with normal renal function was 73.6% and this was diminished in patients with renal impairment. A linear relationship between K13 of cefoxitin and creatinine clearance was demonstrated. The dosage regimen for patients with renal impairment should be adjusted by modifying the dosage interval whilst maintaining the amount administered.
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  • 40
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    European journal of clinical pharmacology 16 (1979), S. 133-139 
    ISSN: 1432-1041
    Keywords: theophylline ; asthma ; pharmacokinetics ; children
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six children, aged 2 months – 4 years, received theophylline 5–6 mg/kg intravenously. Its disposition could be described by a two-compartment open model, the mean serum half life (t1/2 β) was 3.75 h, i. e., shorter than in adults, but there was a considerable interindividual variation (1.8–7.0 h, in one patient 13.3 h). Thirteen children (2 months – 4 years) received theophylline suppositories in a dose of 3.8–5.0 mg/kg, and ten (6 months – 4 years) in a dose of 8.4–14.5 mg/kg. Absorption was slow (mean half-time 43 min), incomplete and variable (biological availability 8–100%, mean 80%). Only four of the patients given the higher dose and none given the lower dose reached a therapeutic serum concentration (10–20 µg/ml). Nine children (6 months – 4 years) received rectal enemas of theophylline 4.1–9.2 mg/kg. Absorbtion was rapid (mean half-time 5.5 min) and biological availability averaged 100%. Six patients reached a serum concentration within the therapeutic range. Using the mean values of the calculated pharmacokinetic parameters, rectal enemas providing a dose of theophylline of 6–8 mg/kg t. i. d. were computed to give serum concentrations between 8–20 µg/ml, without producing too high a level during the absorption phase.
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  • 41
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    European journal of clinical pharmacology 16 (1979), S. 279-285 
    ISSN: 1432-1041
    Keywords: salicylate ; synovitis ; osteoarthritis ; arthritis ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Samples of blood and joint fluid from 30 patients who had taken buffered acetylsalicylic acid were examined for concentrations of total salicylates (TSA), acetylsalicylate (ASA) and salicylate (SA). The data were arranged in groups according to diagnosis of the joint disease. Analysis of the data did not show significant difference in the kinetics of TSA into blood. In groups the time to first appearance of 0.3 mg/l averaged 6.3 min for TSA; these values averaged 7.7 min for ASA and 10.9 min for SA. Close to maximum concentrations in blood averaged 18.9 mg/l for TSA, 3.3 mg/l for ASA, and 23.3 mg/l for SA. The time for first appearance of 0.3 mg/l of total salicylates in joint fluid ranged from 10 to 34 min with an average of 18.1 min; the values of ASA averaged 19.4 min and those of SA 21.9 min. The maximum concentration in joint fluid averaged 15.7 mg/l for TSA, 2.5 mg/l for ASA, and 14.5 mg/l for SA. Transport of salicylates from blood to joint fluid showed a pattern consistent with the type of joint disease. Support was found for the hypothesis that diffusion was the major factor in the movement of salicylates from blood to joint fluid.
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  • 42
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    European journal of clinical pharmacology 16 (1979), S. 411-416 
    ISSN: 1432-1041
    Keywords: doxapram ; intravenous infusion regimen ; pharmacokinetics ; data-point weighting ; healthy subjects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of intravenous doxapram in healthy individuals is consistent with a three-compartment open model. Doxapram was administered by bolus injection (1.5 mg · kg−1) and by intravenous infusion (6.5 mg · kg−1 for 2 h) to 5 subjects on separate occasions. There was no significant difference in mean terminal plasma half-lives (355 and 448 min) or in mean total body clearances (5.9 and 5.6 ml · min−1 · kg−1) following i. v. bolus injection or infusion respectively. In 3 subjects plasma doxapram concentrations during and after i. v. infusion agreed with those predicted from pharmacokinetic values obtained from the bolus injection study. Since mean steady-state concentrations (9.9 µg · ml−1) would be reached only after an extended interval (mean 15.2 h), a variable-rate infusion regimen was calculated to produce and maintain a concentration of 2 µg · ml−1 from 15–25 min onwards. A regimen in which the infusion rate is reduced step-wise is recommended to achieve early near-constant plasma doxapram concentrations.
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  • 43
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    European journal of clinical pharmacology 15 (1979), S. 105-108 
    ISSN: 1432-1041
    Keywords: muzolimine ; cardiac failure ; pharmacokinetics ; high ceiling diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of a new “high ceiling” diuretic, muzolimine (Bay g 2821), were investigated after a single oral dose of 40 mg in 7 patients with cardiac failure (Stages I–IV, New York Heart Association classification), and in 2 healthy subjects. Plasma concentrations peaked 1–3 h after administration and declined according to a two-compartment model. The α-phase (distribution phase) lasted until 12–16 h after administration and the mean t1/2α was 3.6 h (range 2.3–4.7) in patients, and 2.6 h (range 2.3–2.9) in healthy subjects. The mean t1/2β was 13.5 h (range 7.4–22.4) in the patients and 14.0 h (range 12.4–14.6) in healthy subjects. T1/2β was not correlated with the degree of heart failure or with the area beneath the plasma concentration curve, which varied three-fold. The renal clearance of muzolimine was in the range 2.7–15.3 ml · min−1 in 5 subjects in whom it was investigated. The pharmacokinetics of muzolimine appear not to be significantly altered by cardiac failure. The prolonged half-lives of the drug are probably responsible for the longer duration of diuretic action reported for muzolimine than for furosemide and bumetamide.
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  • 44
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    European journal of clinical pharmacology 15 (1979), S. 115-120 
    ISSN: 1432-1041
    Keywords: digoxin ; right heart failure ; absorption ; absolute bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption of digoxin has been investigated in 8 patients before and after successful treatment of severe right heart failure.3H-digoxin 0.1 mg as a solution, and un-labelled digoxin 0.25 mg as a tablet, were given to fasted patients. Blood samples were taken at various time intervals up to 120 hours and urine was collected over the same period. The concentrations of labelled digoxin in plasma and urine were measured in a liquid scintillation counter, unlabelled digoxin was estimated by radioimmunoassay, and various pharmacokinetic parameters were calculated. There was no significant difference in the plasma concentration curves in severe right heart failure and after its successful treatment, nor did any of the calculated pharmacokinetic parameters change significantly. Therefore, inhibition of the absorption of digoxin appears unlikely. In an additional study to estimate absolute bioavailability two different groups of patients in severe right heart failure were given3H-digoxin 0.1 mg or unlabelled digoxin 0.25 mg i. v. and the pharmacokinetic parameters were compared with those from the previous study. The bioavailability of the3H-digoxin solution and of the digoxin tablet were in the same range as values previously published for healthy volunteers, and patients both with and without cardiac failure.
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  • 45
    ISSN: 1432-1041
    Keywords: metoprolol ; tachycardia ; healthy subjects ; conventional tablets ; slow release tablets ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma levels and associated reduction in exercise-induced tachycardia have been examined following the administration of single doses of metoprolol in conventional and slow-release tablets at different times to six healthy male subjects. The study was carried out in two parts. Initially, the tablets were given at 9 a. m. and the subjects were studied up to 14 h and then at 24 h. Subsequently, the same doses were given at 9 p. m. and the subjects were studied 12–24 h after drug administration (i. e. 9 a. m.–9 p. m. the next day). After giving the slow-release tablets the peak plasma levels were significantly lower but the drug persisted in the plasma at higher levels than after the conventional tablet. However, the beta-blocking effect was comparable from the two dosages. The results obtained for the period 12–24 h after the evening dose differed from the corresponding values after morning administration in that the plasma levels were higher and the betablocking effects more marked. Furthermore, the half-life values calculated from these data were significantly longer.
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  • 46
    ISSN: 1432-1041
    Keywords: triamterene ; pharmacokinetics ; diuretic effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The plasma and urinary levels of triamterene and two metabolites were measured using a specific method of analysis. Urinary excretion was completed after 48 h, which permitted a rough estimate of its half-life as longer than two hours. The areas under the curve were 672.5±160.3 and 1.311.3±399.1 µg/ml × h after the triameterene 150 mg and 300 mg p.o., respectively and correspondingly 4.2±1.4% and 3.7±0.6% of the dose were excreted as unchanged drug. The principal metabolite of triamterene found was the sulfate conjugate. The area under the curve of this metabolite amounted to 6.672±2.120 and 11.941±5.005 µg/ml × h after the of 150 mg and 300 mg triamterene doses, respectively. The urinary excretion of the metabolite varied between 25.0±4.0% and 17.5±3.5% of the dose after either dose. In healthy subjects an effect on sodium excretion was observed after a dose of 150 mg, whereas the potassium-retaining effect was observed only after the dose of 300 mg.
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  • 47
    ISSN: 1432-072X
    Keywords: Ethanol inhibition ; Solute accumulation ; Saccharomyces cerevisiae ; Plasma membrane ; Lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Incorporation of ethanol (1.0 or 1.25 M) into exponential-phase cultures of Saccharomyces cerevisiae NCYC 366 growing anaerobically in a medium supplemented with ergosterol and an unsaturated fatty acid caused a retardation in growth rate, which was greater when the medium contained oleic rather than linoleic acid. Ethanol incorporation led to an immediate drop in growth rate, and ethanol-containing cultures grew at the slower rate for at least 10 h. Incorporation of ethanol (0.5 M) into buffered (pH 4.5) cell suspensions containing d-[6-3H] glucose, d-[1-14C] glucosamine, l-[U-14C] lysine or arginine, or KH2 32PO4 lowered the rate of solute accumulation by cells. Rates of accumulation of glucose, lysine and arginine were retarded to a greater extent when cells had been grown in the presence of oleic rather than linoleic acid. This difference was not observed with accumulation of phosphate. Ethanol was extracted from exponential-phase cells by four different methods. Cells grown in the presence of linoleic acid contained a slightly, but consistently, lower concentration of ethanol than cells grown in oleic acid-containing medium. The ethanol concentration in cells was 5–7 times greater than that in the cell-free medium.
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  • 48
    ISSN: 1432-072X
    Keywords: Sulfur dioxide ; Sulfite ; Air polluting substances ; Saccharomyces cerevisiae ; ATP hydrolysis ; Reversibility of sulfite effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sulfite, at concentrations above 1 mM and at a pH below 4, caused cell death in Saccharomyces cerevisiae X2180 as measured by the colony-forming capacity. A rapid decrease in the ATP content was observed prior to cellular death. The depletion of ATP was reversible and the lethal effect could be prevented if the cells were exposed to sulfite for periods of less than 1 h. Extent and rate of ATP depletion were dependent on time, pH value, temperature and sulfite concentrations.
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  • 49
    ISSN: 1432-0878
    Keywords: Catecholamine synthesizing enzymes ; Adrenal medulla ; Embryonic induction ; Adrenocortical hormones ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cellular localization of the enzymes tyrosine hydroxylase (TH), aromatic amino-acid decarboxylase (or dopa decarboxylase, DDC), dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla of adult rats and rat fetuses (14th, 17th, 18th, 19th and 21st day) was examined. In the prenatal stages the medullary blastema and an adjacent part of the primitive sympathetic trunk were also investigated. Tissues were fixed in ice-cold 4% paraformaldehyde in 0.1 M phosphate buffer (pH 7.2). Cryostat sections (10 μm in thickness) were stained by the indirect immunofluorescence technique. Rabbit antibodies to TH (isolated from human pheochromocytoma), DDC, DBH and PNMT (the latter three isolated from bovine adrenal medulla) were used. Sections incubated with serum of non-immunized rabbits were used as controls. In the adult adrenal medulla, two cell types can be distinguished. One cell type contains only TH, DDC and DBH. The other cell type contains PNMT in addition. It is concluded that these cells correspond to the noradrenaline-(NA-) and adrenaline-(A-)storing cells respectively. In all prenatal stages TH, DDC and DBH are found in the primitive sympathetic trunk, in the medullary blastema, and in the medullary cells which have migrated into the cortical “anlage”. PNMT is observed for the first time on the 18th day. Moreover, PNMT could only be demonstrated inside the adrenal gland. From these observations it is concluded that the capacity to synthesize NA is developed even before the “medullary” cells have reached the cortical “anlage”. On the contrary, the capacity to synthesize A seems to be acquired only after this contact is established. The hypothesis is put forward that this phenomenon might indicate the induction of PNMT by glucocorticoids secreted by the fetal cortex.
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  • 50
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    Cell & tissue research 200 (1979), S. 135-146 
    ISSN: 1432-0878
    Keywords: Arcuate nucleus ; Cytogenesis ; Synaptogenesis ; Neuropil ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Morphogenesis of the arcuate nucleus of the rat from the 15th fetal day to the 6th postnatal day was investigated light and electron microscopically. The arcuate neurons exhibit a gradual development after the 15th fetal day. All cytoplasmic constituents are present in these nerve cells already during the last days of gestation. Nevertheless, they are not fully differentiated at birth. The first synapse-like structures (presynapses) were observed in 17 day-old, the first synapses in 18 day-old fetuses. During the early postnatal period the number of presynapses decreases, but at the same time there is a gradual increase in the number of the relatively mature synapses. This process starts already during the last days of prenatal life. Although all structural elements of the arcuate nucleus of the adult rat appear to be present at birth, the extent of the neuropil area and the number of the presynapses indicate that the arcuate nucleus is still in a fairly undeveloped stage during the first postnatal days.
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  • 51
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    Cell & tissue research 200 (1979), S. 329-334 
    ISSN: 1432-0878
    Keywords: Median eminence ; Axon terminals ; Tanycytes ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present ultrastructural study proves the existence of nerve terminals closely apposed to the plasmalemmata of tanycytes in the rat median eminence. Several of these “axo-tanycytic” endings display remarkable accumulations of agranular endoplasmic reticulum in the form of pleomorphic vesicles which are closely apposed on either side of the plasma membrane of each cell compartment. Some of these vesicular profiles give the impression of structural continuity across both membrane systems. This phenomenon is discussed in the context of being a potential substratum for communication between both cell compartments.
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  • 52
    ISSN: 1432-0878
    Keywords: Vomeronasal organ ; Membrane particles ; Cell contacts ; Freeze-etching ; Rat
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    Topics: Biology , Medicine
    Notes: Summary The free surfaces and cell contacts in the epithelia of the vomeronasal organ of the rat were investigated by freeze-etching. The microvilli of receptor cells show a lower density of intramembranous particles (IMP) than the microvilli in the receptor-free epithelium. The ratio between the IMP on P and E-face is approximately 11∶1 in the receptor terminals, and 3.5∶1 in the cilia and microvilli of the receptor-free epithelium. Although atypical in length and only poorly equipped with rootlet fibers, the cilia of the receptor-free epithelium are furnished with typical ciliary necklace structures of up to 10 rows of membrane particles. Differences in the density of IMP on the P-faces of different cilia are probably due to continual ciliogenesis and also due to the different age of cilia in the receptor-free epithelium. Zonulae occludentes show different configurations in the neuroepithelium and in the receptor-free epithelium. In the former, they show a tendency to cross-link and form facet-like patterns, reflecting a constant morphology and relative stability for this apical region. In the receptor-free epithelium the junctional rows of zonulae occludentes display only loosely interconnected networks and a tendency to orient parallel to each other and to the free surface. In addition to zonulae occludentes, typical square aggregations of IMP are observed in the receptor-free epithelium. They are not exclusively restricted to the zone of intensive cell contacts by means of fine interdigitating cell processes, and their function has yet to be identified experimentally.
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  • 53
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    Cell & tissue research 200 (1979), S. 163-177 
    ISSN: 1432-0878
    Keywords: Gastrin cells ; Entero-endocrine cells ; Rat ; Cell isolation ; Pylorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A technique has been developed to obtain viable, isolated and enriched populations of gastrin cells (G-cells) from the rat stomach. Restricted tissue samples from a small area of the pyloric antrum known to be particularly rich in G-cells, were sequentially digested with pronase followed by mechanical agitation, to remove the epithelial cells. This technique resulted in a significant enrichment of G-cells (3–4 fold) since the surface epithelial cells and upper portions of the glands were discarded before the initial G-cell fraction was collected. These cells in suspension were then isolated from each other by gentle pipetting in a DNase containing solution and designated the crude preparation (CP). The G-cells were then purified further by separating the cells according to size by velocity sedimentation. The greatest concentration of G-cells (15–25 %) was found in the fraction containing cells with diameters of 10 to 12 μm. The effectiveness of the technique was evaluated by counting G-cells as identified by electron microscopy and immunofluorescence and assessing gastrin activity by radioimmunoassay. All three methods indicated that cell separation by gravity velocity sedimentation enriched the G-cell population 15–20 fold over their concentration in the CP. The combined techniques of selective pronase digestion followed by gravity velocity sedimentation resulted in an isolated cell preparation containing a 50–100 fold increase of G-cells over their normal distribution in the intact gastric mucosa. Since these isolated G-cells retain features indicating viability, their usefulness for in vitro studies is suggested.
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  • 54
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    Cell & tissue research 200 (1979), S. 29-33 
    ISSN: 1432-0878
    Keywords: Magnocellular neurosecretory system ; Activation ; Rat ; Vasopressinergic neurons ; Oxytocinergic neurons ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The activated hypothalamic magnocellular neurosecretory system of the rat was studied in tissue sections, double stained with the unlabeled antibody peroxidase-antiperoxidase complex (PAP) technique. The results indicate that in animals with an activated hypothalamic magnocellular neuroendocrine system, as well as in normal animals, vasopressin and oxytocin are exclusively synthesized in separate vasopressinergic and oxytocinergic neurons.
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  • 55
    ISSN: 1432-0878
    Keywords: LH-RH neurons ; Hypothalamus ; Rat ; Immunohistochemistry ; Radioimmunoassay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The location of the perikarya of LH-RH neurons in the rat hypothalamus and their pathways to the median eminence were studied by immunohistochemistry and radioimmunoassay after placing stereotaxic electrolytic lesions in several parts of the hypothalamus. The principal location of the cell somata was found to be in the ventral part of the medial preoptic area; their pathways were classified into a main baso-lateral pathway and an accessory descending pathway branching off from the former. The main pathway was found to cross in the vicinity of the corresponding neuronal perikarya. The central median eminence and the dorsal and ventral walls of the tubero-infundibular sulcus of the caudal part of the median eminence are innervated mainly by the baso-lateral pathway. On the other hand, the rostral and most caudal portions of the median eminence are innervated principally by the descending pathway and have a subsidiary dual innervation. The projection of LH-RH neurons to the OVLT is believed to originate from perikarya adjacent to this circumventricular organ.
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  • 56
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    Cell & tissue research 198 (1979), S. 427-433 
    ISSN: 1432-0878
    Keywords: Arcuate nucleus ; Rat ; Hypothalamic deafferentation ; Synaptic plasticity ; Estrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In order to examine the effect of estrogen on the synaptic structures in the hypothalamic arcuate nucleus (ARCN), semi-quantitative studies were performed by counting synapses in an 18,000 μm2 area in the middle part of the ARCN in each brain. In ovariectomized female rats injected with 2 μg of estradiol benzoate (EB) for three weeks, the mean numbers of axodendritic and axosomatic synapses were not significantly different from those in the intact and ovariectomized controls. When the medial basal hypothalamus (MBH) including the ARCN was isolated by use of a Halász knife (MBH island), the mean number of axodendritic synapses was decreased to about half of the controls. However, EB treatment for three weeks from the day of surgery effectively restored the axodendritic synaptic population of the deafferented ARCN. This may suggest that estrogen has a facilitatory effect on axodendritic synapse formation in the deafferented ARCN, presumably by stimulating axonal sprouting and synaptic regeneration of intact axons in the MBH island.
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  • 57
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    Cell & tissue research 198 (1979), S. 441-454 
    ISSN: 1432-0878
    Keywords: Testis ; Rat ; Seminiferous tubule ; Transitional zone ; Fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An electron microscopic study was made on the structure of the testicular transitional zone (TZ) in the adult rat. The TZ proper consists of modified Sertoli cells, with only a few spermatogonia and macrophages, surrounding distally a very narrow lumen. The TZ Sertoli cells have nuclei with a somewhat coarser matrix and more peripheral heterochromatin than Sertoli cell nuclei of the nearby seminiferous tubules, and the electron density of the cytoplasm varies from cell to cell. Smooth endoplasmic reticulum is abundant, but usually there are also scattered ribosomal rosettes and an occasional profile of rough endoplasmic reticulum. Microtubules are very numerous in the columnar portion of the cell, and laminar structures seemingly joining the cell surfaces are sometimes seen. Lipid droplets and lysosomal structures are frequent cellular components in proximal TZ Sertoli cells. Empty intracellular vacuoles are abundant, sometimes arranged around areas of smooth endoplasmic reticulum. Occasionally, membrane-limited fine granules and vacuoles are seen within Sertoli cells and also in the TZ lumen, suggesting a possible secretory activity by these cells. The apical processes of the Sertoli cells form large vacuolar structures, and in the basal parts of the epithelium vacuoles with capillary-like appearance are frequently seen. Phagocytosis of germinal cells by the Sertoli cells occurs in the proximal region of the TZ. Round waste bodies in contact with the Sertoli cell apices protruding into the tubulus rectus, are also common. The tunica propria of the TZ is thickened and somewhat wrinkled, and in the proximal region the myoid cell layer loses its continuity and is replaced by fibroblasts. The epithelium of the tubulus rectus adjacent to the TZ consists of several overlapping epithelial cells. The typical junctional complexes between TZ Sertoli cells appear to be impermeable to the lanthanum tracer.
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  • 58
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    Cell & tissue research 199 (1979), S. 483-492 
    ISSN: 1432-0878
    Keywords: Pituitary gland ; Rat ; Luteotroph cells ; Pimozide ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of pimozide, a dopamine receptor-blocking agent, were studied in the pars distalis of the rat. The animals received 100μg/100 g pimozide daily for 5, 10, 15, and 20 days. Pimozide induces striking ultrastructural changes after 5 days of treatment. The number of luteotroph (LTH) cells is significantly increased; they display characteristics of stimulation. The extrusion of granules into the intercellular space via exocytosis is frequently observed. The intercellular spaces are highly dilated, forming a lacunar system filled with an amorphous material, erythrocytes and involuted LTH cells. Transitional stages in the process of involution are observed in LTH cells. Luteotroph cells also form a syncytium. Twenty days after treatment the abovedescribed changes decrease in magnitude. The present findings suggest that pimozide stimulates the mechanism of synthesis and release in the luteotroph cells, an effect that is less evident with longer treatment.
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  • 59
    ISSN: 1432-0878
    Keywords: Pars distalis ; Graft ; Ultrastructure ; Prolactin ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intact female rats received transplants of two hypophysial partes distales under the kidney capsule. The plasma levels of prolactin were determined, and the ultrastructure of the grafted gland was studied 15, 45 and 90 days after the operation. Although prolactin levels in the three experimental groups were significantly higher than those in control rats, a decrease in prolactin level was detected in the 45-day samples. Parallel ultrastructural changes suggest that between the 45th and 90th postoperative day a process is initiated leading to hyperplasia and hypertrophy of prolactotrophs.
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  • 60
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    Cell & tissue research 199 (1979), S. 271-279 
    ISSN: 1432-0878
    Keywords: Subsurface cisterns ; Neurons ; Paraventricular nucleus ; Hypothalamus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Structures identified as subsurface cisterns (SSC's) were found in neurons of the paraventricular nuclei of the rat hypothalamus. They appeared as cytoplasmic organelles consisting most often of stacks of parallel cisterns apposed to the neuronal plasmalemma. These SSC's were located in the interneurons of the parvocellular system, but not in neurosecretory cells and glial cells. SSC's were seen at zones of cytoplasm apposed to neuronal or glial cell processes, showing in some instances specific relationships with synaptic areas. The morphological features of these SSC's are described, and their possible functional significance is briefly discussed.
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  • 61
    ISSN: 1432-0878
    Keywords: Hypothalamo-hypophysial system ; Rat ; Tanycytes ; Ontogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The differentiation of tanycytes was studied light and electron microscopically during the perinatal period in rats, the time when functional connections between hypothalamus and hypophysis are established. The 3rd ventricle is slit-like between 16 and 18 days of the prenatal period. Its wall is formed by intensively proliferating matrix cells with apical processes, ovoid perikarya and a basal process. The ventral region of the 3rd ventricle becomes funnel-shaped on the 20th day of the prenatal period. As the cells differentiate, the apical process becomes shorter and broader. Moreover, on day 20 of prenatal life cells without apical processes appear. Their number increases during the postnatal period. The concentration of endoplasmic reticulum, mitochondria, polysomes, lipid droplets, dense bodies (lysosomes), lamellated and multivesicular bodies increases. Initially the cells are similar but from the 3rd day of postnatal life differentiation occurs in different regions of the infundibular recess. After the 5th day, there are no marked changes in the structure and distribution of these cells.
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  • 62
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    Cell & tissue research 201 (1979), S. 377-408 
    ISSN: 1432-0878
    Keywords: Median eminence ; Tanycytes ; Nerve tracts ; Regional organization ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structural organization of the rostral, lateral and postinfundibular regions of the median eminence (ME) of 5-day cyclic diestrous rats was studied with light and electron microscopic methods. The ependymal cells lining (i) the floor of the infundibular recess (IR) at rostral levels, (ii) the lateral extensions of the IR, and (iii) the floor of the premammillary recess appear to represent the same type of tanycyte ependyma (β1 tanycytes). In the entire width of the rostral and postinfundibular palisade regions, as well as in the lateral palisade region of the preinfundibular ME, the processes of the β1 tanycytes form a continuous cuff. This cuff separates the nerve endings from the blood vessels and the pars tuberalis. At this level, synaptoid contacts between neurosecretory axons and the ependymal cuff can be observed. The ultrastructural characteristics of the β1 tanycytes are described and their ependymal endings tentatively classified into three types. In the lateral regions of the ME, the Golgi study revealed the presence of two fiber systems: (i) one possessing a latero-medial trajectory and distributed in the subependymal region; (ii) the other formed by a loose longitudinal tract originating from neurons of the arcuate nucleus. Some functional implications of the cellular organization of the rat ME are discussed.
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  • 63
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    Cell & tissue research 201 (1979), S. 349-359 
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Rat ; Somatostatin-containing neurons ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The rat hypothalamus was studied at the light microscopic level with the use of single and double immunocytochemical staining methods. It was shown that the rat supraoptic and paraventricular hypothalamic nuclei, and their accessory neurosecretory nuclei, do not contain magnocellular somatostatin neurons. The distribution of the hypothalamic parvocellular somatostatin cells is described. The parvocellular component of the rat hypothalamic paraventricular nucleus is, at least partly, composed of somatostatin cells: they form a fairly well circumscribed periventricular cell mass. The rat suprachiasmatic nuclei contain separate somatostatin neurons and vasopressin neurons. Scattered somatostatin cells are present in the entire arcuate nucleus. In addition to the periventricular somatostatin cells located in the preopticanterior hypothalamic area and in the arcuate nucleus, the rat hypothalamus also contains numerous scattered somatostatin cells located distant from the third ventricle.
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  • 64
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    Cell & tissue research 201 (1979), S. 93-99 
    ISSN: 1432-0878
    Keywords: Pituitary cell ; Gonadotrophs ; Culture ; Cell lines ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Gonadotroph-rich cell lines were established from multipotential pituitary clonal cells (2A8) which were implanted under kidney capsule of hypophysectomized female rats. These cell lines secrete gonadotrophins (FSH and LH) continuously over two months after establishment; LHRH stimulated the secretion of hormones into the culture medium. Many of the cells reacted immunohistochemically to antiserum to FSH or LH, while a small number reacted to antiserum to prolactin or TSH. They did not contain normal secretory granules such as those of gonadotrophs in vivo.
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  • 65
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    Cell & tissue research 201 (1979), S. 499-502 
    ISSN: 1432-0878
    Keywords: Monoamine fluorescence ; Microfluorometry ; Computer-assisted correction ; Hypothalamus ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a circumscribed area of the preoptic periventricular nucleus of a male rat, formaldehyde-induced monoamine fluorophores modified by treatment with HCl vapors were investigated microfluorometrically (measurement of excitation peak ratio 370∶320 nm) in all fluorescent terminals and preterminals. Microfluorometric recordings of an individual fluorescent structure were performed without UV irradiation of neighboring fluorophores. Recorded data were sampled and corrected by a microcomputer (WangPCS II). 19 neuronal processes (axons) contained noradrenaline fluorophores; 11 contained dopamine fluorophores; 6 exhibited uncharacteristic excitation peak ratios; and in 9 recordings technical problems did not allow identification of the fluorophore content.
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  • 66
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    Cell & tissue research 202 (1979), S. 1-7 
    ISSN: 1432-0878
    Keywords: Matrix vesicles ; Normal bone ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The occurrence of vesicles in the extracellular matrix of alveolar bone of normal young rats was demonstrated by both ultrastructural and enzymatic studies. Transmission electron microscopy revealed abundant vesicles in the matrix. The presence of hydroxyapatite crystals, both within the vesicles and in the matrix, was affiliated with rupture of the vesicular membrane. Calcifying nodules were scarce. High levels of both specific and total activities of alkalineand pyrophosphatases were found in the fraction of isolated vesicles. This fraction also showed activities of different ATPases and acid phosphatase.
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  • 67
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Serotonin ; Quantitative light and electron microscopic radioautography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Serotonin containing structures in the median eminence of the rat have been studied by quantitative light and electron microscopic radioautography following intraventricular infusion of tritiated 5-hydroxytryptophan. One hour after injection of the tracer the highest density of silver grains was recorded in the ependymal and external zones, especially in the lateral palisade zone. The proportion of labelled neurosecretory terminals was also larger in the lateral palisade zone (29%) as compared with the medial palisade zone (13%), although the mean number of developed silver grains per one terminal was higher in the latter. On the average, 16% of neurosecretory terminals sequestered radiolabelled 5-hydroxytryptophan in the external zone of the rat median eminence. It is suggested that serotonin, like catecholamines, is discharged from neurosecretory terminals localized in the external zone and via the portal circulation affects the function of the anterior pituitary. The sites of origin of serotoninergic structures of the median eminence as well as the possible role of monoamine (catecholamine and indolamine) neurohormones in a dual peptidergic and monoaminergic control of anterior pituitary functions are discussed.
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  • 68
    ISSN: 1573-8744
    Keywords: lorazepam ; benzodiazepines ; pharmacokinetics ; drug accumulation ; antipyrine
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    Topics: Chemistry and Pharmacology
    Notes: Abstract Six healthy volunteers participated in single- and multiple-dose pharmacokinetic studies of oral lorazepam. Following single 4-mg oral doses, peak plasma lorazepam concentrations ranging from 40 to 70 ng/ml were reached within 3 hr of the dose. Values of absorption half-life averaged 25min (range 10.3–42.7min), and elimination half-life (t 1/2β ) averaged 14.2 hr (range 8.4–23.9 hr). During 15 consecutive days of 3 mg per day administered in divided doses, accumulation to the steady-state condition was complete within several days of the initiation of therapy. Values of accumulation half-life (mean 21.1 hr) were slightly longer than t 1/2β , and the two were not well correlated. Observed accumulation ratios (mean 1.88) were very close to those predicted from the single-dose study (mean 1.77), but the correlation between the two (r=0.51) was not significant in the small sample size. “Washout” half-life values (mean 14.9 hr) were highly correlated with t 1/2β (r=0.92). Clearance of a single intravenous dose of antipyrine determined prior to the multiple- dose lorazepam study (mean 0.86 ml/min/kg) was essentially identical to that determined after the study (mean 0.87 ml/min/kg). Overall, the rate and extent of lorazepam accumulation during multiple dosage were reasonably well predicted by the single-dose kinetic study. However, accurate prediction for any specific individual was not always achieved. Stimulation or inhibition by lorazepam of its own clearance probably does not explain imprecise prediction, since single-dose t 1/2β .
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  • 69
    ISSN: 1573-8744
    Keywords: procainamide ; pharmacokinetics ; constant-rate infusion ; acetylator phenotype ; pharmacogenetics ; renal impairment
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of procainamide was determined in 21 lidocaine-resistant patients who received the drug according to a pharmacokinetically designed double-infusion technique. Thirteen patients were phenotyped as slow acetylators, seven as fast, and one as intermediate. The total body clearances (ClT) of PA in slow and fast acetylators were 22.6 and 34.8 liters/hr, respectively. The fraction of PA cleared by the formation of NAPA in the corresponding acetylator group was 0.2 and 0.4. Renal impairment affected the pharmacokinetics of PA more profoundly as the ClTs of PA in patients with and without renal impairment were 17.9 and 31.2 liters/hr, respectively. None of the calculated volumes of distribution was affected by acetylator phenotype or renal impairment. These data identify the contribution of at least two of the major factors accounting for variability in PA disposition in patients undergoing therapy.
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  • 70
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 249-264 
    ISSN: 1573-8744
    Keywords: dexamethasone ; pharmacokinetics ; renal excretion ; high-performance liquid chromatography
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of dexamethasone alcohol is described in six male and six female healthy adult volunteers who each received 8 mg of dexamethasone phosphate by bolus intravenous injection. Quantitation of the alcohol was done using a high-performance liquid Chromatographic method with improved specificity. Statistical evaluation of the results generated by nonlinear least-squares regression analysis of the plasma concentration-time data shows that the phosphate ester is very rapidly hydrolyzed to the alcohol and a biexponential equation is the simplest poly exponential equation that is consistent with the data. The terminal phase half-lifet 1/2β was significantly greater (p〈0.05) in males (mean 201.5 min) than in females (mean 142.3 min). The prolongedt 1/2β in males did not appear to be caused by an impaired capacity to eliminate dexamethasone since the total plasma clearance did not differ between males (mean 247.5ml/min) and females (mean 242.9 ml/min). There was, however, a high positive correlation betweent 1/2β and $$V_{d_{ss} } $$ among the 12 adults (r=0.92, p〈0.001). There were also significant correlations between $$V_{d_{ss} } $$ and body weight (r=0.67, p〈0.05) andt 1/2β (r=0.80, p〈0.01).The difference in body weight between the sexes seems to be the main factor contributing to the difference observed in t 1/2β. An average of only 2.6% of the dose was found unchanged in a 24-hr urine sample, and hence it appears that dexamethasone is primarily eliminated by extrarenal, probably hepatic, mechanisms.
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  • 71
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 383-396 
    ISSN: 1573-8744
    Keywords: chlorpheniramine ; pharmacokinetics ; oral absorption ; first-pass effect ; saturation kinetics
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of chlorpheniramine has been studied in six dogs by following the time course of plasma concentration of the drug after intravenous and oral administration of its maleate salt in solution form. After intravenous dosing the decline in chlorpheniramine plasma concentration was typically biexponential. The drug distributed rapidly and extensively to the extravascular tissues. The mean distribution phase halflife was 12.5 min, and the mean apparent volume of distribution, Vdβ, was 525% ofthe body weight in four dogs with normal hematocrits. The mean half-life of elimination was 1.7hr. The percent absolute availability following oral administration of the drug in the aqueous solution form was found to be dose dependent. At 100-mg dose, in six dogs, an average of 36% of the orally administered dose was found to be systemically available. At 50-mg dose, in one of the four dogs studied, no measurable plasma levels of chlorpheniramine were obtained, and the average bioavailability was only 9.4%. The average availability in four dogs at 200-mg dose was 39.4%. Even at 200-mg oral dose, the dogs did not show any signs of sedation and remained alert all through the experiment. Saturable first-pass gut and/or hepatic elimination has been postulated. The possible implications of these findings on the therapeutic effectiveness of the usual dosing regimen of chlorpheniramine in dogs are discussed.
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  • 72
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 481-494 
    ISSN: 1573-8744
    Keywords: clonidine ; pharmacokinetics ; blood and brain levels ; liver clearance
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    Topics: Chemistry and Pharmacology
    Notes: Abstract To investigate the pharmacokinetic behavior of clonidine, rats were given clonidine intravenously at 125, 250, and 500μg/kg and blood clonidine concentrations were followed for 6 hr. The disposition of clonidine in two brain regions was studied in rats after an i. v. dose of 500 μg/kg. The liver clearance in rats was investigated by liver perfusion techniques. The results obtained indicate that the disposition characteristics of clonidine can be described by a two-compartment open model in both rats and cats. The penetration of clonidine into tissues is rapid, and brain levels in rats were about 1.7 times higher than blood levels. Brain tissues were found to be an indistinguisible part of the central (blood) compartment. Dose-dependent pharmacokinetic behavior was found for clonidine in rats at the doses used. This was demonstrated by a decrease of both the rate constant of distribution to the peripheral compartment and the overall elimination rate constant from the body, with increase in dose. As a consequence, the volume of distribution and the clearance both decreased with increasing dose. Possible explanations for the dose-dependent behavior of clonidine are discussed.
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  • 73
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 527-536 
    ISSN: 1573-8744
    Keywords: instantaneous distribution ; pharmacokinetics ; pulmonary first-pass effect
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The classical concept of assuming that an i.v. dose instantaneously distributes into the central or plasma compartment is reviewed, as is the potential for pulmonary first-pass effect. Based on available literature, the concept is shown to lead to serious errors in estimating pharmacokinetic parameters, particularly for drugs with high clearance.
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  • 74
    ISSN: 1573-8744
    Keywords: clonidine ; pharmacokinetics ; analgesia ; blood pressure effects ; smooth muscle
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The time course of an observed pharmacological effect is affected not only by the kinetics of the drug levels at the site of action but also by parameters such as the slope and maximum effect of the functional relationship between drug level and response. Using clonidine as a test drug, it was found that the kinetics of its effects on blood pressure and pain responses cannot be described by the time course of clonidine levels in the blood, brain, or the hypothetical tissue compartment of the two-compartment characteristics of this drug. However, the results can be explained assuming that the observed pharmacological effects of a drug are composed of the sum of responses from at least two receptor sites with different slopes and maximal effects. The effect of intravenously administered clonidine on blood pressure in the rat was found to be related to the blood concentrations at least at two receptor sites with opposite effects, one leading to a hypertensive and the other to a hypotensive response. Predictions indicate that a maximum decrease of arterial blood pressure is obtained when the steady-state blood concentration of clonidine is about 1 ng/ml and that no effect is seen at 10 ng/ml. Higher levels will produce an increase of the pressure. The kinetics of the analgesic effect of clonidine in the rat could best be related to the brain levels if the observed effect was considered to be derived from the sum of activity at two receptor sites each producing analgesia. The kinetics of the effects of clonidine on the nictitating membrane of the cat was found to be determined by the kinetics of the drug in the peripheral compartment of the two-compartment open model. Consideration of multiple receptor responses is suggested for future studies on the relationship between the kinetics of drug levels and pharmacological responses.
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  • 75
    ISSN: 1573-8744
    Keywords: digoxin ; pharmacokinetics ; response kinetics ; three-compartment model ; serum digoxin kinetics ; systolic time intervals ; radioimmunoassay
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    Topics: Chemistry and Pharmacology
    Notes: Abstract A study designed to investigate the relationship between the pharmacokinetics of digoxin and a measure of its pharmacological effect has been conducted. Serum digoxin concentrations and systolic time intervals were measured concurrently in 12 normal male volunteers following a 1.0 mg i.v. bolus injection. The averaged serum digoxin concentration- time and response-time data were analyzed pharmacokinetically using a three-compartment open model and nonlinear least- squares fitting. When only the serum level-time data were analyzed, a close relationship was found between calculated digoxin levels in the slowly distributing (deep) peripheral compartment and response of the heart to digoxin, as measured by changes in the QS2 index δQS2I. Although it was not possible to distinguish clearly a linear from a nonlinear relationship between digoxin levels in the deep compartment and δQS2I, the nonlinear relationship gave the best overall fit when both serum digoxin and δQS2I data were fitted simultaneously. The simultaneous fityielded a total body clearance of digoxin of 3.6 ml/min/kg and a terminal t1/2 of 42 hr.
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  • 76
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 87-95 
    ISSN: 1573-8744
    Keywords: clonazepam ; in vivo biotransformation ; 7-amino metabolite ; pharmacokinetics ; monkeys ; anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetic behavior of the 7-amino metabolite of clonazepam administered exogenously and formed endogenously from the parent drug was studied in a group of rhesus monkeys using constant rate intravenous infusions. Plasma levels of the 7-amino metabolite and/or clonazepam were determined with a GC-CI-MS method. The biological half-life of the 7-amino metabolite (2.2 ± 1.0 hr) was shorter than that of clonazepam (4.9 ± 0.2 hr). Total body clearance of the metabolite (0.83 ± 0.16 liters/hr/kg) was larger than that of the parent drug (0.55 ± 0.09 liters/hr/kg). The kinetics of in vivo biotransformation were described by a two- compartment model in which formation and disposition of the metabolite follow first-order processes. The fraction of a dose of clonazepam appearing in the systemic circulation as 7-amino metabolite was 0.70 ± 0.30. This value may underestimate the actual fraction formed, if the metabolite is susceptible to first- pass metabolism following in situ formation.
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  • 77
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 265-274 
    ISSN: 1573-8744
    Keywords: furosemide ; indomethacin ; prostaglandin ; pharmacokinetics ; pharma-codynamics
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics and pharmacodynamics of intravenous furosemide, 40 mg, were studied in four normal males in a crossover fashion with and without indomethacin pretreatment. In each study 16 plasma and 10 urine samples were collected over 24 hr. Fluid and electrolyte urinary losses were replaced orally throughout the study. Unchanged furosemide and indomethacin were measured using HPLC; urinary sodium was measured by flame photometry. Pretreatment with indomethacin resulted in increased and prolonged furosemide plasma levels, increased area under the curve, decreased plasma clearance, decreased renal clearance, increased half-life, no change in volume of distribution, and decreased sodium excretion and urine volume. Analysis of sodium excretion rate with time shows that the inhibiting effect of indomethacin was greater during the first 2 hr than at later times.
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  • 78
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 453-462 
    ISSN: 1573-8744
    Keywords: pheneturide ; antiepileptics ; pharmacokinetics ; TLC-UV densitometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pharmacokinetics of pheneturide (a decarboxylation product of phenobarbital), used to prevent psychomotor seizures for many years, was studied in normal human volunteers. To measure the drug in plasma and urine, a highly sensitive and reproducible thin-layer chromatography-reflectance spectrophotometric assay was developed. The results show that pheneturide follows first-order kinetics in the dose range studied. Its half-life after single doses is 54 hr (range 31–90), and its total body clearance (100% nonrenal) is 2.6 liters/hr (range 1.73–3.59). After repetitive administration, half-life is 40 hr (but clearance remains unchanged because of a lower volume of distribution). Because of the long half-life, repetitive administration results in a continuous steady-state level and makes this drug (kinetically) ideal for long-term use.
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  • 79
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    Journal of pharmacokinetics and pharmacodynamics 7 (1979), S. 471-479 
    ISSN: 1573-8744
    Keywords: metoprolol ; α-OH-metoprolol ; active metabolites ; pharmacokinetics ; β- blocking effect
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    Topics: Chemistry and Pharmacology
    Notes: Abstract The plasma levels and the β- blocking effect of metoprolol and its active metabolite α- hydroxymetoprolol have been studied after i.v. bolus injections of the substances to dogs. For both substances the β- blockade increased with the dose, and there was a linear relationship between percent reduction in exercise heart rate and the logarithm of plasma concentration. The dose of the metabolite, however, had to be 5 times higher than that of metoprolol to induce the same degree of β- blockade. Because of differences in the volume of distribution, 2.0 liters/kg for α- OH-metoprolol and 3.5 liters/kg for metoprolol, the 5 times higher dose of α- OH-metoprolol resulted in 10 times higher plasma levels of the metabolite than of metoprolol. α- OH-Metoprolol was more slowly eliminated (t1/2∼7.0 hr, total body clearance ∼3.5 ml-kg−1-min−1) than metoprolol (t1/2∼2.0 hr, total body clearance ∼20.0 ml-kg−1-min−1). Approximately 5% of an i.v. dose of metoprolol was metabolized to α- OH-metoprolol. The half-life of the endogenously formed metabolite was the same as after an i.v. dose of the compound.
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  • 80
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    Journal of chemical ecology 5 (1979), S. 909-918 
    ISSN: 1573-1561
    Keywords: Attractants ; nematodes ; Panagrellus redivivus ; Rhabditis oxycerca ; Saccharomyces cerevisiae ; predacious fungi ; methyl acetate ; ethyl acetate ; propyl acetate ; butyl acetate ; amyl acetate ; ethyl formate ; propyl formate ; amyl formate ; ethyl propionate ; sodium methyl dithiocarbamate
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The free-living nematodesPanagrellus redivivus andRhabditis oxycerca are strongly attracted to methyl, ethyl, propyl, butyl, and amyl acetate, to ethyl, propyl, and amyl formate and to ethyl propionate, but all the respective alcohols and acids are without effect. No loss of attraction is observed when the attractants are combined with lethal concentrations of the commercial nematicide sodium methyl dithiocarbamate.
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  • 81
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    Cell & tissue research 197 (1979), S. 443-451 
    ISSN: 1432-0878
    Keywords: Ameloblasts ; Cell death ; Incisors ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The migration of the ameloblasts in the continuously erupting incisors of the rat is accompanied by cell loss. Ameloblasts degenerate near the mesial and lateral cemento-enamel junctions in the secretory zone and in the middle two thirds of the region of postsecretory transition, degeneration being most marked where these areas merge. These findings support the hypothesis that the prism decussation in the enamel results from alternating transverse rows of secretory ameloblasts sliding past each other whilst elaborating their rods. The distribution of the degenerating cells suggests, however, that the sliding cell rows are not exactly transverse but arcuate, with the opening facing incisally. The progress of structural alterations of the nuclei in the degenerating ameloblasts appears to follow the pattern earlier described in vinblastine-damaged ameloblasts.
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  • 82
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    Cell & tissue research 198 (1979), S. 145-158 
    ISSN: 1432-0878
    Keywords: Dorsal prostate gland ; Rat ; Apocrine secretion ; Prolactin
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    Topics: Biology , Medicine
    Notes: Summary Rat dorsal prostate epithelium was studied in intact adult animals, in animals castrated for three days and in rats after inhibition of prolactin secretion. Thin sections, electron-microscopic autoradiographs and freeze-fracture replicas were used to analyze the process of apocrine secretion in this gland. The rough endoplasmic reticulum and the Golgi apparatus of the secretory cells are well developed, but secretory granules are absent. The only sign indicating release of secretory material is the appearance of blebs originating from the apical plasma membrane. Freeze-fracture replicas of the apical plasma membrane reveal that the blebs develop randomly from the bases of microvilli-like protrusions. In vitro pulse labeling of the proteins using 3H-leucine resulted in a labeling of the apical blebs. A post-castration period of three days was sufficient to reduce drastically the number and size of the apical blebs concomitant with regressive changes of the cell. Suppression of prolactin secretion for three weeks by application of lisuride, a synthetic ergot alkaloid, also induced regressive changes in the secretory cells. The apical blebs were still present, but they were shrunken and their content appeared condensed. These experimental conditions proved that the apical blebs are closely related to the functional activity of the cells and are interpreted as true apocrine secretion in the rat dorsal epithelium.
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  • 83
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    Cell & tissue research 203 (1979), S. 223-229 
    ISSN: 1432-0878
    Keywords: Nuclear inclusions ; Neurons ; Paraventricular nucleus ; Hypothalamus ; Rat
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    Topics: Biology , Medicine
    Notes: Summary This paper deals with the ultrastructure of two types of intranuclear inclusions, “microfilamentous spindle-shaped” and “crystalloid”, present in paraventricular nucleus neurons of adult normal rats. These inclusions appear occasionally in some non-secretory neurons of the parvocellular system, but have never been seen in neurosecretory cells of the magnocellular system. The microfilamentous spindle-shaped inclusions show a close spatial relationship with the granulofibrillar body and interchromatin granules. The distribution and functional significance of such structures are discussed in the light of recent ultrastructural and biochemical studies on nuclear inclusions.
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  • 84
    ISSN: 1432-0878
    Keywords: Median eminence ; Rat ; Catecholamines ; Quantitative light and electron microscopic radioautography
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    Topics: Biology , Medicine
    Notes: Summary By means of light and electron microscopic radioautography a quantitative study of the regional distribution of catecholamines in the median eminence of the rat was carried out. One hour after intraventricular injection of 3H-dopamine the highest radioautographic reaction was recorded in the external zone, especially in the lateral palisade zone where many neurosecretory terminals are separated from the basal lamina of the portal pericapillary space by a glial “cuff”. This area showed the highest percentage (52%) of labelled catecholamine containing neurosecretory terminals as well as the maximal silver grain density per one terminal. In the medial palisade zone where direct neurovascular contacts with the capillary loops prevail, only 27 per cent of neurosecretory terminals were found to harbour tritiated dopamine. On the average 35 per cent of neurosecretory terminals in the median eminence of the rat contain catecholamines (both dopamine and noradrenaline). Pretreatment of animals with reserpine strongly reduced the binding of the label. Per cent of labelled neurosecretory terminals as well as grain density over terminals were decreased in both the medial and lateral palisade zones, although to a lesser degree in the latter. The site of origin of catecholamine fibers as well as the mode of catecholamine action at the level of the median eminence are discussed.
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    Cell & tissue research 204 (1979), S. 127-140 
    ISSN: 1432-0878
    Keywords: Somatostatin-like activity ; Retina ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A somatostatin-like substance is demonstrated by light microscopic immunohistochemistry (PAP-method) in perikarya and cell processes of the retina of adult and infant rats. These perikarya are identified according to their size, arrangement and distribution. Each of the first two neuronal orders (receptors, bipolar cells, ganglionic cells) of the visual pathway can be associated with retinal cells reacting positively with anti-somatostatin. In the adult rat, perikarya and processes of (i) horizontal cells, (ii) amacrine cells and (iii) large neurons in the ganglionic layer are specifically labeled. The staining of middle-sized and small ganglion cells is probably caused by the close attachment of labeled fibers to non-reacting cells. Postnatally, the immunoreactive elements develop in parallel to the differentiation of the corresponding retinal layers. It is discussed whether the three types of retinal cells containing a somatostatin-like substance provide an inhibitory system to each of the two orders of retinal neurons.
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  • 86
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    Cell & tissue research 196 (1979), S. 147-151 
    ISSN: 1432-0878
    Keywords: Submaxillary salivary gland ; Secretory granules ; Glycoproteins ; Effect of heat ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Secretory granule area and glycoprotein concentration of the saliva in the submaxillary gland of rats were measured during various stages of acclimation to heat at 34±1° C. Granule size decreased by 18% during the first five days of heat acclimation (0.025〈p〈0.05) after which period it increased to reach 118% of the control levels after 28 days (p〈0.05). Glycoprotein concentration in the saliva of stimulated glands rose above control levels, reaching a maximum between the 2nd and 5th day of acclimation (p〈0.05). It was concluded that the initial decrease in granule size reflects a decrease in glycoprotein content following an increase in salivary flow known to occur at high ambient temperatures. The subsequent increase in granule size is considered an adaptation of the gland to continuous stimulation. The rise in salivary glycoprotein concentration suggests increased efficiency of the secretory mechanism.
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  • 87
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Median eminence ; Intraependymal cisternae ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Structure, three-dimensional arrangement and ontogeny of large intracellular cisternae located in the median eminence region of the rat hypothalamus were studied using toluidin-blue stained semithin sections and electron microscopy. The cisternae occur along the projections of ependymal cells lining the ventral portion of the third ventricle (infundibular recess). Small cisternae can be seen close to the ventricle, whereas larger ones, divided into smaller compartments by thin septa, cluster near the surface of the hypothalamus. The cisternae are encompassed by a thin layer of cytoplasm to which axon terminals containing synaptic and dense core vesicles are closely related. Cisternae are arranged around the median eminence in a characteristic pattern. They occupy the midline in the retrochiasmatic area, flank both margins of the median eminence and extend caudally behind the origin of the pituitary stalk. The cisternae appear first between the 15th and 17th postnatal days. At about the 30th day their size and distribution resemble the situation observed in adult animals. The ependymal cisternae are suggested to be closely related to the luteinizing-hormone releasing-hormone (LH-RH)-containing fibers.
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  • 88
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    Cell & tissue research 197 (1979), S. 337-346 
    ISSN: 1432-0878
    Keywords: Development ; Median eminence ; Neurohypophysial hormones ; Corticotrophin releasing factor ; Immunoperoxidase histochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Transverse sections of the median eminence from fetal and neonatal rats were examined by the immunoperoxidase technique to detect the presence of oxytocin, vasopressin and neurophysin. Neurophysin was observed in the 18-day fetus. Vasopressin and oxytocin were not detected until after birth, on the 4th and 8th days respectively. There was an accumulation of material crossreactive with neurophysin and vasopressin antibodies in the palisade layer of the median eminence between the 4th and 9th days after birth. This distribution of immunoreactive material in the palisade layer was suggestive of neurosecretory substances localized in two fibre tracts on either side of the median eminence. The data are consistent with the accumulation of corticotropin releasing factor and an associated neurophysin in this area. It is suggested that the accumulation of material occurs because of the relative immaturity of the capillary loops that constitute the primary plexus of the hypophysial portal system.
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  • 89
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    Cell & tissue research 196 (1979), S. 237-247 
    ISSN: 1432-0878
    Keywords: Liver ; Kupffer cells ; G6PDH activity ; Histochemistry ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The aim of this study was to identify the G6PDH-active sinusoidal cells in the rat liver described by Rieder et al. (1978). Because of their number and distribution in the liver parenchyma, endothelial cells and pit cells could be excluded. Fat-storing cells were specifically marked by vital staining with vitamin A and identified by fluorescence microscopy. Kupffer cells could be detected after vital staining with carmine. Both staining methods allowed a subsequent incubation for the demonstration of G6PDH activity in the same unfixed cryostat section. Whereas more than 80% of the fluorescent particles were found outside the enzyme-positive cells, all G6PDH-active cells contained carmine particles. After counting the G6PDH-active cells, an estimation of 0.217 × 108 cells/g liver tissue was obtained. The results indicate that high G6PDH activity is common to all Kupffer cells, and is therefore a highly specific marker enzyme for this class of sinusoidal liver cells.
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  • 90
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Hypothalamo-hindbrain pathway ; Rat ; Blood pressure ; Milk ejection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. In lactating rats and in rats deprived of water, the amount of neurosecretory material in the fibres of the neurosecretory hypothalamohindbrain pathway exceeds that in untreated control animals. Under these experimental conditions the pathway and its target regions can be well analysed by means of fluorescence and electron microscopic methods. 2. The axons belonging to the hypothalamo-hindbrain pathway originate from perikarya located in the caudal portion of the nucleus paraventricularis and also from a small group of perikarya in the caudo-lateral hypothalamus. On the way to the hindbrain the neurosecretory fibres join other fibre bundles of the mid- and hindbrain. 3. In the hindbrain most of the neurosecretory fibres terminate in the area of the nucleus tractus solitarii and in the area of the dorsal column nuclei. The axon terminals form synapses with other neurones. 4. Using cytochemical methods at the ultrastructural level (Naumann and Sterba, 1976), the authors were able to prove that the vesicles in the exohypothalamic fibres and in their synaptic terminals contain the same sort of material as the neurophysin vesicles in the posterior lobe of the hypophysis. 5. The most distinct increase in neurophysin was observed in lactating females which were separated from their sucklings after a normal lactation period of 15 days and killed four days thereafter, and in rats deprived of water for different time periods. 6. The relationship of the neurosecretory hypothalamo-hindbrain pathway to the nucleus tractus solitarii and to the dorsal column nuclei suggests that, functionally, there may be a correlation between the system of blood-pressure control and the milk ejection reflex.
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  • 91
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    Calcified tissue international 25 (1978), S. 75-83 
    ISSN: 1432-0827
    Keywords: Rat ; Fluorosis ; Enamel ; Scanning electron microscopy ; Low temperature incineration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Sixteen 58-day-old male rats of Wistar strain, with a mean body weight of 179 g, were divided into two equal groups. Each group of eight animals was maintained for 70 days on drinking water, ad lib., containing no fluorine (control group) and 100 ppm of fluorine (experimental group). All specimens examined were obtained from the incisal portions of the incisors. The following types of enamel specimens were prepared for scanning electron microscopy: (1) acid-etched specimens; (2) acid-etched specimens followed by low temperature microincineration; and (3) fractured specimens. The enamel formed during high fluoride exposure showed marked hypocalcification, that is, the crystallite density in the prism core and interprismatic region was lower than that of control animals. The organic substances appeared to increase in these regions. These changes were prominent in the outer and middle enamel layers. Such changes following fluoride administration appear to indicate an inhibition of enamel maturation, that is, an inhibition of the mineral deposition and/or an inhibition of organic matrix withdrawal.
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  • 92
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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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  • 93
    ISSN: 1432-1041
    Keywords: p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    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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  • 94
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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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  • 95
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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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  • 96
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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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  • 97
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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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  • 98
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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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  • 99
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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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  • 100
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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
    Source: Springer Online Journal Archives 1860-2000
    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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