Double-blind evaluation of ritodrine sustained release for oral maintenance of tocolysis after active preterm labour

Objective To evaluate the effect of ritodrine sustained release capsules for maintaining uterine quiescence after successful treatment of active preterm labour. Design Multicentre placebo-controlled trial. Setting Five teaching hospitals in the Netherlands. Participants Women (n = 95) at less than 35 weeks of gestation in whom active preterm labour had been stopped with intravenous ritodrine. Interventions Women received either two 40 mg ritodrine sustained release capsules (n = 50) or identical placebo capsules (n = 45) three times a day for seven days. Results The proportion of women who received another course of active treatment was significantly smaller with the sustained release than with placebo (1 of 50 versus 11 of 45: P = 0.003) as was the number delivering because of preterm labour during treatment (0 of 50 versus 4 of 45: P = 0.04). There were no other significant differences between the two groups. Conclusions Maintenance treatment with ritodrine sustained release capsules after arrest of preterm labour reduces the risk of recurrences of preterm labour that necessitate treatment or precipitate delivery.