Two dose regimens of nifedipine for management of preterm labor: a randomized controlled trial

We compared two dose regimens of tocolytic oral nifedipine. Women with singleton pregnancies admitted in preterm labor (24 to 34 weeks) were randomized to high-dose (HD) nifedipine ( N = 49; 20 mg loading dose, repeated in 30 minutes, daily 120 to 160 mg slow-release nifedipine for 48 hours followed by 80 to 120 mg daily until 36 weeks) or low-dose (LD) nifedipine ( N = 53; 10 mg, up to four doses every 15 minutes, daily 60 to 80 mg slow-release nifedipine for 48 hours followed by 60 mg daily until 36 weeks). Uterine quiescence at 48 hours (primary outcome); delivery at 48 hours, 34 and 37 weeks; and recurrent preterm labor were similar. Gestational age at delivery was higher in HD (36.0 +/- 2.8 versus 34.7 +/- 3.7 weeks, P = 0.049). Rescue treatment was needed more in LD (24.5 versus 50.9%, odds ratio = 0.3; 95% confidence interval 0.1 to 0.7). Maternal adverse effects, birth weight, intensive care nursery admission, and composite neonatal morbidity were similar. However, neonatal mechanical ventilation was needed less and nursery stay was shorter in HD. HD nifedipine does not seem to have an advantage over LD in achieving uterine quiescence at 48 hours. Further studies should address the optimal dose and formulation of tocolytic nifedipine.