I. D. Bradbrook

Pharmacokinetics of intravenous cyclophosphamide in man, estimated by gas-liquid chromatography.

SummaryA simple gas chromatographic assay utilising alkali flame ionisation detection is described for the estimation of cyclophosphamide as its trifluoroacetate derivative from plasma. Examination of five patients following intravenous cyclophosphamide gave values of 8.9 h (SD 2.7) for the half-life and 0.061 liters/h/kg (SD 0.011) for whole-body clearance of the drug.

Pharmacokinetics of intravenous glibenclamide investigated by a high performance liquid chromatographic assay.

SummaryA simple high performance liquid Chromatographic assay for the determination of plasma glibenclamide concentrations is described. This resolved glibenclamide from normal plasma constituents. The calibration curve of the assay was linear over the range 10–500 μg/1 and the minimum level of detection was 2 μg/1. Within-assay coefficients of variation were 11.6% (20 μg/1); 5.3% (50 μg/1); 6.8% (100 μg/1); between-assay coefficients of variation were 8.4% (20 μg/1); 4.7% (50 μg/1) and 7.4% (100 μg/1). The assay was used to study the pharmacokinetics of a 1 mg intravenous dose of glibenclamide in eight normal subjects. The mean half-life was found to be 1.47±0.42 h (SD) and no evidence for a non-linear β-phase or slowly equilibrating ‘deep’ compartment was found although this could not be rigorously excluded. The mean systemic drug clearance was 78±29 ml·h-1·kg-1 and the apparent volume of distribution in the β-phase was 155±44 ml/kg. The median time of maximum response of plasma immunoreactive insulin was 25 min and the median time of maximum blood glucose response was 53 min. No correlation could be found between the pharmacokinetics of glibenclamide and these responses in fasted normal individuals.

Plasma mexiletine concentrations following combined oral and intramuscular administration

SummaryMexiletine in doses of 50, 100 and 400 mg was administered by intramuscular injection to a healthy subject and the resulting plasma concentrations were compared with those after 100 mg given intravenously. The bioavailability of mexiletine given by this route is complete and the kinetics are linear with dose. Plasma mexiletine concentrations resulting from 200 mg given orally with either two 4-ml intramuscular injections each containing 100 mg (Mexitil® — for intravenous use) or one 2-ml intramuscular injection of an experimental preparation containing 200 mg were compared in 3 and 6 normal subjects respectively. Plasma levels within the therapeutic range of 0.75–2 µg/ml were attained at mean times of 28.7 and 42.5 min respectively. Apart from raised plasma creatine phosphokinase levels (as would be expected following an intramuscular injection) the tolerability of intramuscular mexiletine injections was satisfactory. Further studies in patients will be required to determine whether the combined oral and intramuscular administration of mexiletine is of value in acute myocardial infarction.

The effects of domperidone on the absorption of levodopa in normal subjects

SummaryThe effect of simultaneous oral administration of 20, 40, or 80 mg domperidone on the pharmacokinetics of an oral 500 mg dose of levodopa was studied in eight normal women. No significant differences in maximum plasma levodopa concentration, the time of its attainment, or the area under the plasma levodopa concentration versus time profile occurred. Domperidone significantly reduced the incidence of adverse gastrointestinal effects due to levodopa administration.

High-performance liquid chromatographic assay for simultaneous estimation of aminoglutethimide and acethylamidoglutethimide in biological fluids

SummaryA simple rapid high-performance liquid chromatographic assay for simultaneous estimation of aminoglutethimide and its acetylated metabolite acetylamidoglutethimide in plasma, saliva, and urine is described. This assay is suitable for pharmacokinetic studies in normal subjects and patients receiving other medication in addition to aminoglutethimide.

Study of Repeated Administration of Fenbufen in Patients with Chronic Rheumatic Disorders and Renal Impairment

Male and female patients suffering from rheumatoid arthritis with normal renal function or with renal impairment were treated in hospital with 300 mg of fenbufen 8 hourly for fourteen days. Concentrations of fenbufen and its principal metabolites were measured by high pressure liquid chromatography on days 0, 7, 10 and 14 and also four days after discontinuation of the drug. Renal impairment does not produce cumulation of either fenbufen or its major metabolites in the plasma. The metabolite profile of the drug was similar to that observed in patients with normal renal function.