Treatment of preterm labor with the oxytocin antagonist atosiban: a double-bind, randomized, controlled comparison with salbutamol

Abstract

Objective: To compare the efficacy and safety of atosiban and salbutamol in the treatment of preterm labor. Study design: A multicenter, double-blind, double-placebo, randomized, controlled trial. Women (n=241) diagnosed with preterm labor at 23–33 gestational weeks were enrolled and received either atosiban (n=119) or salbutamol (n=122). At randomization, women were stratified by gestational age (≤28 weeks and >28 weeks). Atosiban (i.v. bolus dose of 6.75 mg, then 300 μg/min for 3 h and 100 μg/min for up to 48 h) and salbutamol (2.5–45 μg/min) were administered by i.v. infusion for up to 48 h. Retreatment with study drug or an alternative tocolytic agent was allowed. Main outcome measures included tocolytic effectiveness which was assessed in terms of the number of women undelivered after 48 h and 7 days. Tocolytic efficacy and tolerability were assessed in terms of the proportion of women undelivered and who did not require alternative tocolytic therapy at 48 h and 7 days of starting treatment. Safety was assessed in terms of maternal side effects and neonatal morbidity. Results: Tocolytic effectiveness at 48 h was 93.3 versus 95.0% (P=0.67) and after 7 days was 89.9 versus 90.1% (P=0.93) in the atosiban and salbutamol groups, respectively. Tocolytic efficacy and tolerability within 48 h was 79.8 versus 75.2% (P=0.15), and after 7 days was 58.8 versus 46.3% (P=0.021) in the atosiban and salbutamol groups, respectively. Maternal adverse events, including serious events, occurred more frequently in the salbutamol group. Neonatal outcomes were comparable between the study groups. Conclusions: The oxytocin antagonist atosiban was found to be better tolerated by both mother and fetus than salbutamol, with a comparable neonatal and infant safety profile, and atosiban was as effective as salbutamol in delaying threatened preterm birth. This study supports the clinical use of atosiban in the treatment of preterm labor.