Search PubMed⌕ Search

Biomedical subjects

R Gugler

Publications and source records attributed to R Gugler.

At least 127 records · Page 7Linked to original sources
PubMed1977

The bioavailability of phenytoin.

The bioavailability of three commercial products of phenytoin (Epanutin, sodium salt; Phenhydan, calcium salt; Zentropil, free acid) was studied relative to a standard solution of sodium phenytoin. Each preparation was given for 14 days in a daily dose of 300 mg according to a cross over design. The three brands tested were equivalent as to their bioavailability with respect to plasma concentrations during one dosing interval, the area under the plasma level time curve, the time of peak plasma concentration, and the urinary excretion of the primary metabolite. Therefore, these phenytoin brands are bioequivalent and exchangeable for antiepileptic treatment. The standard solution of sodium phenytoin had a higher bioavailability as compared to the commercial products.

Adult↗
PubMed1977

Interlaboratory variability of valproic acid determinations.

19 pooled plasma specimens were sent as unknowns to 13 participating research laboratories. The interlaboratory variability between the results was very high. Only 4 out of 13 laboratories had 6--12% of their results within the 95% confidence limit for each sample. The precision of repeated determinations was fairly good. 6 out of 10 participating laboratories had a coefficient of variation of less then 5%. The reproducibility and the agreement between the different procedures for quantitative analysis of dipropylacetate is similar to that reported for other major antiepileptic drugs.

Laboratories↗
PubMed1976

A rapid gas chromatographic method for the determination of chlorophenoxyisobutyric acid in plasma and urine.

A rapid gas chromatographic method is described for the determination of chlorophenoxyisobutyric acid (the active metabolite of clofibrate) in plasma and urine. The assay involves an extraction into toluene and back-extraction of the chlorophenoxyisobutyric acid and the internal standard (2-naphthoic acid) into the methylating reagent (trimethylanilinium hydroxide). Concentrations of 1 mug/ml in plasma and urine can easily be measured; the precision of the method is 3.3 +/- 0.7% for plasma and 2.7 +/- 0.4% for urine. There is no interference from endogenous compounds or from drugs commonly prescribed together with clofibrate.

Chromatography, Gas↗
PubMed1976

Phenytoin: pharmacokinetics and bioavailability.

The pharmacokinetics of a single 300-mg oral and intravenous and 14 daily 300-mg oral doses of phenytoin were studied in 6 healthy volunteers. The mean plasma elimination t1/2 was the same following intravenous (16.8 +/- 1.3 hr) and oral (17.1 +/- 1.5 hr) doses of phenytoin; however, following chronic oral administration, the t1/2 increased to 18.9 +/- 1.5 hr (p less than 0.05). The absolute bioavailability of an oral dosage form (Dilantin Kapseals) varied from 57.7 to 85.6% when based on the relationship between the corresponding single dose areas under the curve (AUCs). When based on the comparison of the AUC for multiple oral dosing with the single iv dose area, average bioavailability was 85.9% (71.8 to 106.3). Since the variation in the bioavailability and elimination of phenytoin does not allow accurate prediction of the steady-state plasma concentration, monitoring plasma levels may be of special importance.

Administration, Oral↗
PubMed1976

Pharmacokinetics of beta-receptor-blocking agents in relation to their anti-hypertensive effect.

1. Beta-Recptor-blocking drugs are rapidly and completely absorbed after oral administration. Systemic availability is nevertheless incomplete for propranolol, alprenolol and oxprenolol, owing to "first-pass' extraction by the liver. 2. Plasma half-life is between 2 and 4 h, except for sotalol (10-12 h). Plasma elimination of propranolol is reduced with decreased liver blood flow observed in congestive heart failure or during chronic propranolol therapy itself. 3. beta-Receptor blockade is usually achieved in these concentration ranges: propranolol and alprenolol, 50-100 ng/ml; oxprenolol, 500-1000 ng/ml; pindolol, 10-30 ng/ml; sotalol, 2-6 microng/ml. Higher concentrations are often found with high doses administered to hypertensive patients.

Administration, Oral↗
PubMed1976

Drug protein binding and the nephrotic syndrome.

A reduction in plasma albumin concentration, as seen in patients with the nephrotic syndrome, is usually associated with a decrease in plasma protein binding of highly bound drugs. Therefore, the fraction of the unbound drug increases, but the absolute free concentration remains essentially unchanged due to a compensatory reduction in the steady state total plasma concentration. With phenytoin, protein binding and plasma albumin concentration are closely related, so that the degree of binding can be estimated without specific binding techniques. To be able to correctly interprete plasma levels the degree of protein binding should be known, since a reduced total concentration may be fully effective, if the free drug fraction is increased in hypoalbuminaemic patients. Although the mean steady state plasma concentration of highly bound drugs is not affected in the nephrotic syndrome, a greater fluctuation of the unbound level is observed between doses, offering a possible explanation for the increased incidence of toxicity in hypoalbuminaemic patients. As a consequence, shorter dosing intervals of these drugs seems to be advisable, rather than a reduction in the total daily dose. Reduced protein binding is accompanied by an increase in the total plasma clearance which is a function of the elimination rate constant and the volume of distribution.

Antipyrine↗
PubMed1975

Disposition of quercetin in man after single oral and intravenous doses.

The pharmacokinetics of quercetin, a flavonoid, have been studied in 6 volunteers after single intravenous (100 mg) and oral (4 g) doses. The data after iv administration were analyzed according to a two compartment open model with half lives of 8.8 +/- 1.2 min for the alpha phase and 2.4 +/- 0.2 h for the beta phase (predominant half life), respectively. Protein binding was greater than 98%. The apparent volume of distribution was small at 0.34 +/- 0.03 1/kg. Of the intravenous dose 7.4 +/- 1.2% was excreted in urine as a conjugated metabolite, and 0.65 +/- 0.1% was excreted unchanged. After oral administration no measurable plasma concentrations could be detected, nor was any quercetin found in urine, either unchanged or in a metabolized form. These results exclude absorption of more than 1% of unchanged drug. Recovery in faeces after the oral dose was 53 +/- 5%, which suggests extensive degradation by microorganisms in the gut. The data obtained show that oral administration of flavonoids may be of questionable value.

Administration, Oral↗
PubMed1975

Diphenylhydantoin: correlation between protein binding and albumin concentration.

The unbound fraction of diphenylhydantoin is inversely correlated with the patient's serum albumin concentration and can be accurately estimated graphically without binding analyses. The data for this relationship was obtained from a study in which we observed that the unbound fraction of diphenylhydantoin was two times higher in patients with the nephrotic syndrome. However, in these patients it was not necessary to diminish the dosage since the absolute concentration of unbond drug was unchanged due to a compensatory increase in the apparent volume of distribution and plasma clearance.

Half-Life↗
PubMed1975

The effect of pindolol on exercise-induced cardiac acceleration in relation to plasma levels in man.

The correlation between the beta receptor blocking activity of pindolol and plasma level was studied in 8 subjects after a 10-mg oral dose. Exercise tachycardia was markedly reduced over a period of at least 6 hr. Significant effects were recorded 30 min after the drug. For each individual there was a close correlation between log plasma level and beta blockade. The regression lines were parallel as shown by analysis of covariance; the intercepts, however, were significantly different. It can be concluded that there is a correlation between plasma level and beta adrenergic blockade by pindolol, but the data failed to establish in different individuals the blood levels necessary to achieve effective adrenergic blockade.

Adult↗
PubMed1975

Pharmacokinetics of drugs in patients with the nephrotic syndrome.

Since the binding of drugs to plasma proteins can significantly after the intensity of pharmacological and toxicological effects of drugs, we studied the pharmacokinetics of three drugs in patients with hypoalbuminemia secondary to the nephrotic syndrome, but with relatively normal renal function. No significant differences were seen in the pharmacokinetic parameters observed for antipyrine, a drug which is less than 10% bound to plasms proteins. The percentage of unbound diphenylhydantoin, a highly plasms protein-bound drug, was found in patients with the nephrotic syndrome to be twice that of healthy individuals (19,2 vs. 10.1%, P smaller than 0.001). However, there was also a lower steady-state plasma concentration of diphenylhydantoin (2.9 plus or minus 0.6 vs. 6.8 plus or minus 0.6 mug/ml, P smaller than 0.001) secondary to an increase in the plasms clearance (0.048 plus or minus 0.019 vs. 0.022 plus or minus 0.006 liter/kg.h, P smaller than 0.001) in the nephrotic patients. The net effect is no difference in the absolute concentration of unbound diphenylhydantoin in healthy individuals (0.69 plus or minus 0.05 mug/ml) and patients with the nephrotic syndrome (0.59 plus or minus 0.06 mug/ml). Qualitatively, similar differences were observed with clofibrate. The dose of these drugs need not be routinely reduced in patients with the nephrotic syndrome as long as they have reasonably normal renal function (creatinine clearance greater than 50 ml/min). With all highly bound acidic drugs, knowledge of the concentration of unbound drug is essential to the proper interpretation of total blood levels and subsequent treatment of the patient.

Adult↗