Randomised comparison between a loading and incremental dose model for ritodrine administration in preterm labour

Objective To compare a new loading dose regimen for intravenous ritodrine administration in preterm labour with the conventional dose regimen. Design Multicentre randomised trial using numbered opaque sealed envelopes. Setting Five teaching hospitals in the Netherlands. Participants Women (n = 203) in preterm labour at less than 34 weeks of gestation. Interventions Women received either a loading dose ritodrine infusion followed, tocolysis was reached, by a decrease in infusion rate or the conventional schedule of increasing doses until uterine quiescence was achieved. Results Frequency of successful tocolysis (71%) and duration of treatment (55 h) were similar in both groups, but the loading dose schedule was better tolerated with fewer adverse events. Also the number of dose adjustments was smaller than in the incremental dose group (P < 0.001). Overall, the differences between the two regimens were unexpectedly small. Conclusions Despite the small differences, the loading model is easier to apply, requires fewer dose adjustments, is better tolerated with less side effects, and reduces the likelihood of clinical error.