The oxytocin antagonist atosiban versus the beta-agonist terbutaline in the treatment of preterm labor. A randomized, double-blind, controlled study

Abstract

Objective: To compare the efficacy and safety of atosiban and terbutaline for the inhibition of preterm labor.

Methods: Two hundred and forty-nine women diagnosed with preterm labor at 23-33 weeks of gestation were enrolled of whom 245 women received treatment, 116 with atosiban and 129 with terbutaline. At randomization, women were stratified by gestational age (< or =28 weeks and >28 weeks). Atosiban (iv bolus dose of 6.75 mg, then 300 microg/min for 3 h and 100 microg/min thereafter) and terbutaline (5-20 microg/min) were administered by iv infusion for 13-18 h. Re-treatment with study drug or an alternative tocolytic agent was allowed. Tocolytic effectiveness was assessed in terms of the number of women undelivered after 48 hours and 7 days and efficacy and tolerability in terms of the number of women remaining undelivered and not requiring alternative tocolytic therapy after 48 hours and 7 days of starting therapy. Safety was assessed in terms of maternal side effects and neonatal morbidity.

Results: Tocolytic effectiveness at 48 hours was 86.1% vs 85.3%; p=0.783, and after 7 days it was 76.5% vs 67.4%; p=0.067, in the atosiban and terbutaline groups, respectively. Tocolytic efficacy and tolerability after 48 hours was 72.2% vs 68.2%; p=0.51 and after 7 days was 55.6% vs 43.4%; p=0.08 in the atosiban and terbutaline groups, respectively. Overall, there were fewer clinically important adverse events with atosiban than with terbutaline.

Conclusions: The efficacy of atosiban in the inhibition of preterm labor was shown to be comparable to terbutaline. Atosiban had a superior safety profile compared with terbutaline in terms of maternal and fetal adverse events, and comparable infant outcomes.