Oral Nicardipine versus Intravenous MgSO4 for the Treatment of Preterm Labor

Song, Tae Bok; Kim, Yoon Ha; Na, Jae Ho; Kim, Yong Sik; Kang, Woo Dai; Oh, Yoon Sang; Kang, Myoung Seon; Cho, Moon Kyoung

Abstract

This study was conducted to compare the efficacy and safety of oral nicardipine in acute therapy for preterm labor with those of parenteral magnesium sulfate. Patients between 24 and 34 weeks' gestation with documented preterm labor were randomly assigned to receive oral nicardipine (n=31) or intravenous MgSO4 (n=29) 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 MgSO4 group received a 4 g loading dose for 20 min and then maintenance dose of 2-3 g/hr until uterine contractions were inhibited or side effects became intolerable. Patients could be switched to another tocolytic regimen if they continued to have contractions after 6 hr of therapy. The main outcome variables examined were failure of tocolysis, time to uterine contractions equal or less than 5 times per hour, time to uterine quiescence, time gained in utero, and frequency of adverse medication effects. There were no significant differences in maternal demographic characteristics between the groups. Successful tocolysis, defined as cessation of uterine contractons less than 6 hr from initial dose, was observed in 58.1% in the nicardipine group and 41.4% in the MgSO4 group (p=0.194). Among patients with successful tocolysis who responded with uterine quiescence within 6 hr, there was no significant difference in the time to uterine quiescence in the MgSO4 group. Time to uterine contractions equal or less than 5 times per hour from initial treatment showed no significant difference between the two groups with successful tocolysis. The patients in the MgSO4 group had more adverse side effects, mainly nausea and/or vomiting (p=0.010) and chest pain and/or tightness (p=0.038). These results indicated that oral nicardipine is effective, safe, and well-tolerated tocolytic agent and patients who received MgSO4 were more likely to have adverse medication effects.