Tocolytic efficacy of nifedipine versus ritodrine in preterm labor

In India, the rate of preterm birth is high (9.5%) [1]. Adequate neonatal intensive care facilities are available but fairly skewed in their location. Various agents and different routes have been tried for the management of preterm labor. This study was conducted over a period of one year in a teaching hospital in Surat, India, to evaluate the safety and efficacy profile of nifedipine (Depin, Zydus Cadila, Zydus Tower, Satellite Cross Roads Ahmedabad 380015, India) and ritodrine (Ritopar, Mercury Labs Ltd., 2/13–14, GIDC Ind. Est., Vadodara, 390016, India) in the management of preterm labor. A randomized non-controlled trial design was used. Seventy consecutive women with symptoms of preterm labor and fulfilling designated inclusion criteria were recruited, with 35 women (odd numbers) being allocated to ritodrine group and 35 (even numbers) to nifedipine group. Informed consent was taken and the study was approved by the Hospital Ethics Committee. In group A, women received intravenous ritodrine, followed by oral ritodrine, for 72 h. In group B, nifedipine was administered orally for 72 h. Subjects with less than 34 weeks' gestation received injection betamethasone (Betnesol, Glaxo Smith Kline Pharmaceuticals Ltd., Worli, Mumbai, 400 030, India) 12 mg in 2 doses 12 h apart. Uterine activity cessation and maternal side effects were noted. The dosage schedules for nifedipine and ritodrine were based on the recommendations of King et al. [2] and Arias et al. respectively [3]. Both groups were comparable in terms of maternal age, gravidity and parity. Table 1 shows the tocolytic efficacy of the two drugs. Ten (28.6%) women in the ritodrine group delivered within 48 h. In 32 (91.5%) subjects on nifedipine and 22 (62.9%) subjects on ritodrine, labor was delayed by 2 weeks. This observation was statistically significant at p < 0.04. Table 2 shows that 2 neonates (5.7%) in the nifedipine group and 12 (34.2%) in the ritodrine group had one minute Apgar scores < 7. In the ritodrine group, 6 (17.2%) neonates required NICU admission compared to 2 (5.7%) in the nifedipine group. Eight neonates in ritodrine group and 4 in nifedipine group had hyperbilirubinemia. These observations were not statistically significant. Thirty (85.7%) subjects on ritodrine completed therapy, 3 (8.6%) had intolerable side-effects and 5 (14.3%) had failure to arrest progress of labor. No nifedipine-treated woman had side effects of such severity as to warrant discontinuation of treatment. Thus, nifedipine was found to have better tocolytic efficacy and tolerability compared to ritodrine. The limitation of this study is that this was a randomized non-controlled trial and therefore the possibility of a selection bias cannot be ruled out.