Nifedipine as an antihypertensive drug in patients with renal failure--pharmacokinetics and effects.

Pharmacokinetics and pharmacodynamics of nifedipine were studied in 12 patients with renal failure and hypertension, after a single dose and during an 18-week treatment period. The plasma concentrations of nifedipine and its first pyridine metabolite were measured by gas chromatography mass spectrometry. The oral plasma clearance of nifedipine was 1189 +/- 876 ml min-1, and the mean plasma half-life (t1/2) was 5.99 +/- 3.05 h. The pyridine metabolite was not retained. Plasma concentrations of nifedipine were found to be significantly correlated with the effects on blood pressure, forearm blood flow and peripheral resistance, and these effects did not vary with the degree of renal failure. Normotension was achieved in eight of the nine patients observed over a period of 4 months with doses in the range 20-40 mg, administered twice daily. The mean Cr-EDTA clearance remained unchanged during the study (initial value 31.4 +/- 12.3 ml min-1; final value 32.7 +/- 14.4 ml min-1), and in three patients it increased. Nifedipine induces a slight increase in metabolic rate in patients with renal failure, but it is not necessary to modify the dose. It is effective in lowering blood pressure, has mild side-effects and may improve renal function in some patients.