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

Objective. To compare the efficacy and safety of atosiban and terbutaline f or the inhibition of preterm labor. Methods. Two hundred and forty-nine women diagnosed with preterm labor at 2 3-33 weeks of gestation were enrolled of whom 245 women received treatment, 116 with atosiban and 129 with terbutaline. At randomization, women were s tratified by gestational age (less than or equal to 28 weeks and > 28 weeks ). Atosiban (iv bolus dose of 6.75 mg, then 300 mug/min for 3 h and 100 mug / min thereafter) and terbutaline (5-20 mug/min) were administered by iv in fusion for 13-18 h. Re-treatment with study drug or an alternative tocolyti c agent was allowed. Tocolytic effectiveness was assessed in terms of the n umber of women undelivered after 48 hours and 7 days and efficacy and toler ability in terms of the number of women remaining undelivered and not requi ring alternative tocolytic therapy after 48 hours and 7 days of starting th erapy. Safety was assessed in terms of maternal side effects and neonatal m orbidity. Results. Tocolytic effectiveness at 48 hours was 86.1% vs 85.3%; p=0.783, a nd after 7 days it was 76.5% vs 67.4%; p=0.067, in the atosiban and terbuta line groups, respectively. Tocolytic efficacy and tolerability after 48 hou rs was 72.2% vs 68.2%; p=0.51 and after 7 days was 55.6% vs 43.4%; p=0.08 i n the atosiban and terbutaline groups, respectively. Overall, there were fe wer clinically important adverse events with atosiban than with terbutaline . Conclusions. The efficacy of atosiban in the inhibition of preterm labor wa s shown to be comparable to terbutaline. Atosiban had a superior safety pro file compared with terbutaline in terms of maternal and fetal adverse event s, and comparable infant outcomes.