Labetalol pharmacokinetics in pregnancy-induced hypertension.

Pharmacokinetic parameters of oral labetalol were studied in eight women with pregnancy-induced hypertension in the third trimester of pregnancy. Labetalol exhibited rapid absorption; peak serum concentrations of 881 +/- 219 ng/ml occurred at 20 minutes after labetalol ingestion. The terminal elimination half-life (mean, 1.7 +/- 0.27 hours) was found to be shorter than that reported for normotensive volunteers or nonpregnant hypertensive patients (mean, 6 to 8 hours). A mean apparent oral elimination clearance of 21.8 ml/min/kg compared favorably with that seen in other pregnant and nonpregnant populations. Food delayed the time to peak serum concentration to approximately 60 minutes. Labetalol was detected in fetal cord samples and amniotic fluid samples at concentrations approximately 50% and 16% that of simultaneous maternal vein samples, respectively.