Treatment of angina pectoris with nifedipine

Adverse drug reaction reporting and retrospective phenotyping for oxidation polymorphism

A genetically determined impairment in the ability to oxidase sparteine and debrisoquine also affects the oxidation of several other drugs. This impairment in oxidation may result in accumulation of the associated drugs and in an increased susceptibility to adverse reactions from these drugs. Dunedin houses the New Zealand national centre for the collation and study of adverse drug reactions. Included among the reporting schemes is an intensified monitoring system for newly released drugs, in which physicians report all clinical events occurring during treatment with the drugs under surveillance. The centre thus has available extensive records of names and addresses of prescribers and patients who have been reported as experiencing an adverse event while receiving drug therapy. We investigated the association between genetically poor oxidation of sparteine and adverse reactions to drugs selected as possibly sharing the sparteine/debrisoquine oxidation pathway; these included perhexiline, metoprolol, debrisoquine, piroxicam, mianserin and nifedipine. A kit containing instructions, a sparteine capsule and a container for urine collection was sent to physicians who reported adverse reactions or events to one of the above drugs for forwarding to the patient. It appeared possible, after assays of returned urine for sparteine and its metabolites, that adverse reactions to nifedipine were associated with genetically poor oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Twelve hour (trough) plasma nifedipine concentrations during chronic treatment with nifedipine retard

Variation in plasma nifedipine concentrations have been reported and one study has suggested the existence of a subpopulation of poor metabolisers of this drug. We have studied the variability of 12 h plasma nifedipine concentrations in 64 hypertensive patients on long-term nifedipine Retard 20 mg twice daily. A slightly skewed unimodal distribution with a modal concentration of 15 to 30 ng/ml was obtained. No relationship between 12-h plasma levels and debrisoquine hydroxylation phenotype was found.

Accumulation of nifedipine after multiple doses

The single and multiple dose pharmacokinetics of oral nifedipine capsules, 10 mg, have been examined in five patients with peripheral vasospasm. After a single dose, nifedipine was rapidly absorbed in three and slowly absorbed in two patients. Mean bioavailability parameters included a tmax of 2.9 h, a Cmax of 33.3 ng ml-1 and a AUC0-8 h of 113.3 ng h ml-1. After multiple dosing with either 10 or 20 mg every 8 h for 10 days the mean tmax at steady state was 2.1 h while the mean dose-corrected (to 10 mg) Cmax and AUC0-8 h were 51.9 ng ml-1 and 146.9 ng h ml-1, respectively. The mean elimination rate constant was 0.173 h-1 after both single and multiple doses. The mean extent of accumulation of nifedipine, defined as the ratio of AUC0-8 h (steady state)/AUC0-8 h (single dose), was 1.3; we concluded that nifedipine accumulates in the body when it is administered every 8 h. This should be taken into account when predicting steady state serum concentrations and haemodynamic effects of nifedipine from single dose kinetic data.