Pharmacokinetic and pharmacodynamic parameters of oral nifedipine were studied in the immediate postpartum period in eight women with preeclampsia. Peak serum concentrations of 18 +/- 2.1 micrograms/L occurred 40 minutes after ingestion of nifedipine (10 mg). The terminal elimination half-life (mean = 1.35 +/- 0.3 hours) was found to be shorter than that reported for normotensive volunteers or nonpregnant hypertensive women (mean, 3.4 +/- 0.4 hours). A mean apparent oral elimination clearance of 3.3 +/- 1.3 L/hr/kg was more rapid than that found in normal volunteers (mean, 0.49 +/- 0.09 L/hr/kg) or in women with pregnancy-induced hypertension in the third trimester (mean, 2.0 +/- 0.8 L/hr/kg). Initial nadirs in mean arterial pressure were noted at 50 minutes after ingestion of nifedipine, with an average reduction in mean arterial pressure of 13.8 mm Hg. A dosing interval of every 3 to 4 hours is suggested when rapid-release nifedipine is used in the postpartum patient with preeclampsia.