A comparison of tocolysis with nifedipine and atosiban in preterm labor

Aim To compare the effectiveness and safety of nifedipine and atosiban in women with threatened preterm labor. Material and methods The study comprised 111 pregnant women presenting with threatened preterm labor between 30 and 34 weeks of gestation, who were assigned to receive tocolysis with either nifedipine (n=54) or atosiban (n=57). The effectiveness of tocolysis was determined by the duration of pregnancy prolongation (for 48 hours, 7 days, more than 14 days). The primary outcome was the rate of pregnancy prolongation for 48 hours. The safety of tocolytics was assessed by the rate of adverse events in mothers and the neonates. Results Tocolysis failed in eight women receiving nifedipine (14.8%) and two treated with atosiban (3.5%) (p <0.05), and labor occurred within thefirst 24 hours after beginning treatment. In 46 women receiving nifedipine (85.1%) and 55 treated with atosiban (96.5%) pregnancy was prolonged for more than 48 hours (p<0.05). Among them, all births occurred more than 7 days after the initiation of tocolysis. Two women of the atosiban group underwent a second complete treatment course. Full-term births occurred in 15 (27.8%) and 19 (33.3%) women in nifedipine and atosiban group, respectively (p> 0.05%). Mean duration of pregnancy prolongation after the tocolysis with atosiban was 9.2 days longer than after nifedipine (p <0.05). Women receiving nifedipine were more likely to have hot flushes, palpitations, dizziness and hypotension (p <0.01) requiring a dosage reduction and increasing the interval between doses in 14.8% of cases. Eight women in the nifedipine group did not complete the tocolysis protocol due to poor drug tolerance. Of them, in five women tocolysis was ineffective, and they progressed to delivery within 24 hours after admission. After exclusion from the analysis women failing to follow the treatment protocol, no differences were found in the effectiveness of tocolysis with nifedipine and atosiban. After adjusting the groups for multiple pregnancies, the rates of singleton pregnancy prolongation for 48 hours were 88.46% and 95.56% in the nifedipine and atosiban groups, respectively, and did not differ significantly (p> 0.05). However, the duration of pregnancy prolongation was significantly longer in women receiving atosiban (29.37 ± 14.95 days) than nifedipine (20.30 ± 11.95 days) (p <0.01). Conclusion The effectiveness of nifedipine and atosiban in pregnancy prolongation for 48 hours in threatened preterm labor is comparable. However, lower tolerability of nifedipine limits its applicability. Another advantage of atosiban is a longer period of pregnancy prolongation. Further studies are needed to clarify the effectiveness and safety of these drugs in the management of the threatened preterm labor in multiple pregnancies.

preterm labor, tocolytics, atosiban, nifedipine