Drugs 2004; 64 (4): 375-382

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 1. Pathophysiology of Preterm Labour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376 2. Pharmacology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 2.1 Pharmacokinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 3. Clinical Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 3.1 Preliminary Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 3.2 Clinical Evaluation of Atosiban . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 3.2.1 Atosiban versus Placebo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 3.2.2 Atosiban versus β-Adrenoceptor Agonists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 3.2.3 Maintenance Treatment of Preterm Labour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 3.2.4 Atosiban versus Other Tocolytic Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 4. Dosage and Administration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381 Oxytocin antagonists are synthetic analogues that have the nonapeptide strucAbstract ture of oxytocin. They act by competing with oxytocin for receptors in the myometrium. Animal experiments and pilot clinical studies have examined several agents and, of these, atosiban has been the object of extensive clinical trials. In a large placebo-controlled trial with >500 patients, atosiban reduced the number of premature deliveries over 7 days compared with placebo with no more adverse effects than placebo. In large multicentre studies comparing atosiban with β-adrenoceptor agonists, the efficacy of the two medications was similar for pregnancy prolongation for 48 hours and for 7 days. The adverse effects, particularly cardiovascular, were considerably more frequent in the patients receiving β-adrenoceptor agonists, who had to stop treatment significantly more often than the atosiban recipients. No fetal adverse effects were seen with atosiban and, in particular, no effect on baseline fetal heart rate, unlike with the β-adrenoceptor agonists. Neonatal outcome did not differ significantly according to the treatment. The usefulness of maintenance treatment after the initial 48 hours has not been