Pragmatic comparison of beta2-agonist side effects within the Worldwide Atosiban versus Beta Agonists study.

Objective: While beta2-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 beta2-agonist tocolytics.

Study Design: Pragmatic comparison of ritodrine, salbutamol and terbutaline from re-analysis of data obtained within three comparator arms of three simultaneous comparable randomised controlled trials of beta2-agonists against atosiban in 742 women in preterm labour. The prevalence of categoric side effects between treatment groups was analysed using a chi2 test. The differences in continuous variables between treatment groups were analysed in analyses of covariance.

Results: The 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 < or =2.8 mmol/L, respectively) and clinically unimportant.

Conclusion: Side effects were common with all three drugs. Thus, choosing one beta2-agonist over the other to minimise side effects has little rationale, especially now that safer tocolytics are available.