Oral nifedipine pharmacokinetics in pregnancy-induced hypertension.

The pharmacokinetics of oral nifedipine were studied in 15 women with pregnancy-induced hypertension in the third trimester of pregnancy to determine if the drug's disposition was different from that in nonpregnant patients. Peak serum concentrations of 38.6 +/- 18 ng/ml occurred at approximately 40 minutes after ingestion of nifedipine 10 mg. The terminal elimination half-life (mean 1.3 +/- 0.5 hrs) was shorter than that reported for normotensive volunteers and nonpregnant hypertensives after oral dosing. Mean +/- SD apparent elimination clearance of 2.0 +/- 0.8 L/hr/kg was more rapid than that in healthy volunteers (mean 0.49 +/- 0.09 L/hr/kg). Random serum concentrations were progressively higher in patients receiving larger daily doses. Nifedipine was detected in samples of fetal cord blood and amniotic fluid at concentrations approximately 93% and 53% those of simultaneous maternal vein samples, respectively. The findings indicate that nifedipine may achieve greater antihypertensive efficacy in pregnant women if administered at shorter intervals.