Maintenance treatment of preterm labor with the oxytocin antagonist atosiban

administered tocolysis remain at risk of having subsequent episodes of pret erm labor and preterm delivery. Several pharmacologic agents have been used in an attempt to reduce subsequent episodes of preterm labor, and all are associated with significant side effects. Atosiban, an oxytocin receptor an tagonist, is effective in the treatment of an acute episode of preterm labo r. This study was designed to compare the efficacy and safety of atosiban w ith those of placebo maintenance therapy in women with preterm labor who ac hieved uterine quiescence with intravenous atosiban. STUDY DESIGN: A multicenter, double-blind, placebo-controlled trial was des igned for patients in preterm labor who responded to early intravenous trea tment with atosiban. Five hundred thirteen patients were randomly assigned to receive maintenance therapy, 252 to receive atosiban, and 251 to receive matching placebo. Maintenance therapy was administered as a continuous sub cutaneous infusion, via pump, of 30 mu g/min to the end of 36 weeks' gestat ion. The primary end point was the number of days from the start of mainten ance therapy until the first recurrence of labor. A secondary end point was the percentage of patients receiving subsequent intravenous atosiban thera py. RESULTS: The time (median) from the start of maintenance treatment to the f irst recurrence of labor was 32.6 days with atosiban and 27.6 days with pla cebo (P=.02). At least one subsequent intravenous atosiban treatment was ne eded by 61 atosiban patients (23%) and 77 placebo patients (31%). Except fo r injection site reactions, adverse event profiles of atosiban and placebo were comparable. There were 4 neonatal deaths reported in the atosiban grou p and 5 in the placebo group after the start of maintenance therapy. Infant outcomes (including birth weight) were comparable between maintenance and treatment groups. CONCLUSIONS: Maintenance therapy with the oxytocin receptor antagonist atos iban can prolong uterine quiescence after successful treatment of an acute episode of preterm labor with atosiban. Treatment was well tolerated.