Efficacy and safety of nifedipine versus magnesium sulfate in the management of preterm labor: a randomized study.

Objective: Our purpose was to establish the efficacy and safety of nifedipine versus magnesium sulfate in arresting preterm labor and the efficacy of nifedipine versus terbutaline in preventing recurrent labor.
Study Design: Singleton pregnancies at < 34 weeks in preterm labor were randomized to either oral nifedipine or intravenous magnesium sulfate. In case of tocolysis failure ritodrine was added. After labor was arrested, the patients in the nifedipine group were maintained on oral nifedipine, and those in the magnesium sulfate group were treated with oral terbutaline until completing 34 weeks.
Results: Of 100 patients 80 were considered eligible, of whom 39 were randomized to the nifedipine group. Both groups were comparable in terms of a number of entry variables, including cervical examination, contraction frequency, and gestational age. Both drugs were equally effective in arresting labor and delaying delivery > 48 hours, 92% versus 93%. Both study groups had a similar incidence of side effects, although four (10%) of magnesium sulfate-treated patients required drug discontinuation because of severe symptoms. Nifedipine was as effective as terbutaline in preventing recurrent labor, 26% versus 24%, and in achieving a gestation > 34 weeks, 62% versus 68%.
Conclusions: Oral nifedipine is as effective as magnesium sulfate and terbutaline in arresting and preventing idiopathic preterm labor.