A randomized, double-blind trial of oral nifedipine and intravenous labetalol in hypertensive emergencies of pregnancy

Objective: We sought to compare the efficacies of oral nifedipine and intravenous labetalol in the acute management of hypertensive emergencies of pregnancy. Study Design: We performed a randomized double-blind trial of oral nifedipine (10 mg) and intravenous labetalol (20 mg) in 50 peripartum patients with sustained systolic blood pressure of ≥170 mm Hg or diastolic blood pressure of ≥105 mm Hg. Both agents were repeated at sequentially escalating dosages every 20 minutes until a therapeutic goal of systolic blood pressure of <160 mm Hg and diastolic blood pressure of <100 mm Hg was achieved. Crossover occurred if the treatment goal was not achieved after 5 doses. Primary outcome was time to achievement of the therapeutic goal. Secondary outcome variables were agent failure, urinary output, and adverse effects. Data were analyzed by unpaired t test, Mann-Whitney U test, and analysis of variance for repeated measures. Results: The time to achieve the blood pressure goal was significantly shorter with nifedipine (mean ± SD, 25 ± 13.6 minutes) than with labetalol (43.6 ± 25.4 minutes; P = .002). No patients required crossover therapy. Urine output was significantly increased (P< .001) at 1 hour after nifedipine dosing (99 ± 99 mL) compared with labetalol (44.8 ± 19.1 mL) and remained significantly increased at 2, 6, 12, 18, and 24 hours after initial administration. Adverse effects were infrequent. There were no differences in maternal age, gestational age, number of antepartum patients, or enrollment blood pressures between groups. Conclusions: Both oral nifedipine and intravenous labetalol are effective in the management of acute hypertensive emergencies of pregnancy; however, nifedipine controls hypertension more rapidly and is associated with a significant increase in urinary output. (Am J Obstet Gynecol 1999;181:858-61.)