[Which tocolytic drugs in case of preterm labor?]

Because criteria used for the prediction of preterm labor are poorly effective, many patients receive tocolytic therapy in excess during pregnancy. Beta-mimetic agonists are the reference tocolytic drugs in most countries. Their efficacy in prolonging pregnancy compared to a placebo is proven although no benefit in neonatal morbidity or mortality has been demonstrated. Beta-mimetics have many contraindications, and side-effects are frequent. Serious complications such as pulmonary edema and maternal deaths, though rare, have been reported. Recent research has focused on tocolytic drugs with similar efficacy to beta-mimetics but with less side effects. Calcium-channel-blockers and oxytocin antagonists have been compared with beta-agonists in randomized trials. Both have demonstrated similar efficacy in the prolongation of pregnancy for at least 48 hours. Contrary to beta-mimetics, very few interruptions of treatment have been observed with these treatments. Other tocolytic drugs such as cyclooxygenase inhibitors, although effective in prolonging pregnancy, have unacceptable fetal side effects. Progesterone, antispasmodic drugs and magnesium sulfate have been widely used but their efficacy has not been demonstrated. More recent treatments such as NO-donors and cyclooxygenase-II specific antagonists are not sufficiently evaluated. In conclusion, three main classes may be used as first line tocolytic therapy, beta-adrenergic agonists, calcium-channel-blockers, and oxytocin antagonists. The choice among these treatments may be based on contraindications to beta-mimetics, side-effects of the treatment, or even economic reasons.