Pragmatic comparison of β2-agonist side effects within the Worldwide Atosiban versus Beta Agonists Study

ObjectiveWhile β2-agonists for the acute treatment of preterm labour unequivocally reduce the odds of delivery within 48 h and 7 days, they have been associated with substantial maternal and fetal side effects. We aimed to compare side effect profiles of β2-agonist tocolytics.Study designPragmatic comparison of ritodrine, salbutamol and terbutaline from re-analysis of data obtained within three comparator arms of three simultaneous comparable randomised controlled trials of β2-agonists against atosiban in 742 women in preterm labour. The prevalence of categoric side effects between treatment groups was analysed using a χ2 test. The differences in continuous variables between treatment groups were analysed in analyses of covariance.ResultsThe prevalence of categoric side effects was similar with the three drugs, with the exception of the subjective symptom of palpitations (ritodrine 24.0%, terbutaline 9.3% and salbutamol 12.3%, P = 0.003). There were also some differences in maternal diastolic blood pressure (P < 0.001) and serum glucose levels (P < 0.001), although these were small (<3 mmHg and ≤2.8 mmol/L, respectively) and clinically unimportant.ConclusionSide effects were common with all three drugs. Thus, choosing one β2-agonist over the other to minimise side effects has little rationale, especially now that safer tocolytics are available.