Oral nicardipine versus intravenous magnesium sulfate for the treatment of preterm labor

Objective: The aim of this study was to compare the efficacy and safety of oral nicardipine in acute therapy for preterm labor with those of parenteral magnesium sulfate. Study Design: Patients between 24 and 34 weeks’ gestation with documented preterm labor were randomly assigned to receive oral nicardipine (n = 57) or intravenous magnesium sulfate (n = 65) as initial tocolytic therapy. Patients in the nicardipine group received a 40-mg loading dose and then 20 mg every 2 hours as needed to stop contractions (total 80 mg). Patients in the magnesium sulfate group received a 6-g bolus followed by 2 to 4 g/h to provide uterine quiescence. Patients could be switched to another tocolytic regimen if they continued to have contractions after 6 hours of therapy. The main outcome variables examined were time to uterine quiescence, time gained in utero, recurrence of preterm labor, failure of tocolysis, and pertinent maternal and neonatal outcomes. Results: There were no significant differences in maternal demographic characteristics between the groups. Among patients who responded with uterine quiescence within 6 hours, there was a significant decrease in the time to uterine quiescence in the nicardipine group (P< .01). Patients in the magnesium sulfate group were more likely to have recurrence of preterm labor necessitating further tocolytic attempts (P = .048). The patients in the magnesium sulfate group had more adverse side effects, mainly nausea and vomiting (P = .004). There were no differences in birth weight, estimated gestational age at delivery, or neonatal complications between the 2 groups. Conclusions: Oral nicardipine is an effective, safe, and well-tolerated tocolytic agent. In this prospective clinical trial patients randomly assigned to receive oral nicardipine had arrest of preterm labor more rapidly than did those randomly assigned to receive parenteral magnesium sulfate. Patients who received magnesium sulfate were more likely to have adverse medication effects and recurrent preterm labor. (Am J Obstet Gynecol 1999;181:1432-7.)