Treatment of preterm labor with the oxytocin antagonist atosiban.

The purpose of this study was to describe the course of preterm labor in patients receiving a standard intravenous infusion of the oxytocin antagonist atosiban. An open-labeled, non-randomized study was conducted at 4 sites. Successful tocolysis was defined as delay of delivery larger than 48 hours from starting atosiban and no need for an alternate tocolytic. Atosiban was administered by continuous intravenous infusion at a rate of 300 micrograms per minute until uterine contractions were absent for 6 hours, or up to a maximum infusion time of 12 hours. Sixty-two patients of between 20 and 36 weeks' gestation were enrolled over 6 months. One had rupture of membranes and was excluded. Successful tocolysis was noted in 43 of 61 (70.5%). Four delivered spontaneously within 48 hours and 14 (23.0%) required an alternate tocolytic agent. The chance of successful tocolysis was related to the degree of cervical dilation at the start of therapy. Cessation of uterine contractions was noted in 38 patients (62.3%). A decrease in uterine contraction frequency of 50% or more was noted in 50 of 61 patients (82.0%). Four patients reported side effects (nausea, vomiting, headache, dysguesia, chest pain), but in no case did side effects require discontinuation of the medication. Intravenous administration of atosiban is associated with a delay in delivery comparable to that seen with other tocolytics. If this effect is confirmed in planned placebo-controlled trials, its favorable side effect profile may give it a place in the armamentarium.