Validation of a liquid chromatographic-tandem mass spectrometric method for the measurement of (R)-1-[2,3-dihydro-2-oxo-1-pivaloylmethyl-5-(2-pyridyl)-1H-1,4-benzodiazepin-3-yl]-3-(3-methylaminophenyl)urea (YF476) in human plasma.

A sensitive and specific liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method has been validated for the measurement of YF476 in human plasma. The method involves a simple liquid-liquid extraction procedure, chromatography of the extracts on a C(18) column, atmospheric pressure chemical ionisation and detection in the multiple reaction monitoring mode. The calibration line was linear over the concentration range 0.1 ng/ml (the limit of quantification) to 25.0 ng/ml. Intra- and inter-batch precision was <14% and intra- and inter-batch accuracy was <11% over the entire calibration range. The bioanalytical method is robust and has been used for the analysis of many samples from human subjects involved in early clinical studies (Phase I).

The metabolic fate of 11-bromo[15-3H]vincamine in man.

During 5 days following a single oral dose of 3H-11-bromovincamine (40 mg) to two human subjects, means of 55% and 27% of the 3H dose were excreted in the urine and faeces respectively, mainly within 24 and 48 h. Mean plasma concentrations of 3H reached a peak (1900 ng equiv./ml) at 1 h after dosing and declined biphasically with half-lives of 5 h and 11 h which were similar to half-lives for urinary excretion of 3H. Parent drug and 11-bromovincaminic acid were the major dose-related components in plasma at 1.5 and 3 h. Mean plasma concentrations of 11-bromovincamine reached a peak (620 ng/ml) at 0.75 h and declined biphasically with half-lives of about 1 h and 5 h. The major urinary metabolite was 11-bromovincaminic acid (31% dose). Also present in urine were 11-bromovincamine (3%), 11-bromoapovincamine (1%) and 2 unknown metabolites (9% and 6%). Similar metabolites were detected in faecal extracts. If inadequately stored in biological samples, 11-bromovincamine could be hydrolysed to 11-bromovincaminic acid and be epimerised to 11-bromo-epivincamine.

Bioequivalence of a sustained-release isosorbide dinitrate formulation at steady-state.

Isosorbide 2,5-dinitrate and its pharmacologically active metabolites, isosorbide 2-nitrate and isosorbide 5-nitrate, in plasma accumulated to the predicted steady-state after five consecutive oral doses of sustained-release tablets containing 40 mg isosorbide dinitrate at 12-h intervals and after five consecutive oral doses of reference standard-release tablets containing 20 mg at 6-h intervals to 12 subjects in a crossover study. The comparative bioavailability of isosorbide dinitrate, isosorbide 2-nitrate and isosorbide 5-nitrate from the sustained-release tablet was 110 per cent (p greater than 0.05), 89 per cent (p greater than 0.05), and 89 per cent (p less than 0.05), respectively, of that from the reference standard-release tablet. The isosorbide dinitrate plasma level data were the more variable, as expected for a drug of low systemic availability subject to extensive first-pass elimination. The posterior probability that the true bioavailability of isosorbide dinitrate was included within the usually accepted limits of 80-120 per cent was 0.74, a value which is probably insufficient to justify claims of bioequivalence with the reference formulation in respect of extent of availability. In contrast, the posterior probability that the bioavailability of the metabolites isosorbide 2- and 5-nitrate was included within these limits was 0.90 and 0.98, respectively. On the basis of the mononitrate data, these two formulations may be judged bioequivalent in respect of extent of availability despite a formal statistically significant formulation-related effect in the analysis of variance of the isosorbide 5-nitrate bioavailability data. Claims of bioequivalence of isosorbide dinitrate sustained-release formulations may be more economically justified by analysis of the mononitrate plasma concentrations, although concentrations of the formulated parent dinitrate should also be known.

[Bioavailability of isosorbide-5-mononitrate from delayed-action formulations]. / Freisetzung von Isosorbid-5-mononitrat aus Retard-Formulierungen.

The relative bioavailability of isosorbide-5-mononitrate (IS-5-MN) has been determined after a 3-day period of dosing with 20 mg in standard-release reference tablets and sustained-release capsules at 12-h intervals, 40 mg in sustained-release capsules (Olicard 40 retard) at 24-h intervals and after single oral dose of 60 mg sustained-release capsules (Olicard 60 retard), in a cross-over study with 12 human subjects. Accumulation factors of 1.1-fold or 1.2-fold occurred during administration of 20 mg in standard- or sustained-release tablets and capsules respectively at 12-h intervals, and negligible accumulation of drug occurred after administration of 40 mg in sustained-release capsules at 24-h intervals or was calculated by the superposition principle to occur after doses of 60 mg in sustained-release capsules at 24-h intervals. The mean extent of bioavailability of IS-5-MN from the 20 mg, 40 mg and 60 mg sustained-release capsules was 79%, 67% and 70% respectively, of that from the standard-release reference tablets. The posterior probability that the bioavailability of IS-5-MN was included within the limits 60%-90% of the reference tablets was 97%, 86% and 95% for the 20 mg, 40 mg and 60 mg sustained-release capsules respectively. Means of peak plasma levels of IS-5-MN after administration of the sustained-released capsules were linearly related to the doses administered.(ABSTRACT TRUNCATED AT 250 WORDS)