Ritodrine in oral maintenance of tocolysis after active preterm labor: randomized controlled trial.

AIM To assess the efficacy of oral ritodrine in the form of sustained-release capsules for maintenance of uterine quiescence after successful treatment of threatened preterm labor. METHODS We randomized 120 women with singleton pregnancy who were successfully treated for threatened preterm labor before 34 completed weeks to receive either maintenance tocolysis with two 40 mg ritodrine sustained release capsules three times a day (study group, n=62) or no treatment (control group, n=58) for three days. The primary outcome measure was the recurrent episode of threatened preterm labor within 72 hours, which was defined as regular palpable uterine contractions and change in cervical effacement or cervical dilatation on clinical examination. Secondary outcome measures included the incidence of preterm birth, neonatal adverse outcomes, and maternal side effects. RESULTS There was no difference in the frequency of recurrent episodes of threatened preterm labor requiring another course of intravenous treatment between the study (8/62) and control (6/58) group of women (P=0.879). No differences were found between the study and control groups in any of the predefined secondary outcome measures, ie, delivery before 37 weeks (13/62 vs 7/58, respectively; P=0.288), delivery before 34 weeks (3/62 vs 1/58, respectively; P=0.682) and birth weight (3037-/+573 g vs 3223-/+423 g, respectively, P=0.862). There were more reported maternal side effects in the study group than in control group (47/62 vs 23/58, respectively; P(<0.001). CONCLUSIONS Additional maintenance ritodrine therapy was unnecessary in women with singleton pregnancy who had an episode of threatened preterm labor successfully treated with intravenous tocolytic therapy. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT00290173.