Efficacy of Atosiban in Preterm Labor
Atosiban has comparable efficacy to other tocolytics in delaying preterm birth for 48-72 hours, but with a significantly better maternal safety profile, making it a preferred option for short-term tocolysis to allow for administration of antenatal corticosteroids and maternal transfer to appropriate facilities. 1, 2
Mechanism and Clinical Effectiveness
- Atosiban acts through selective, competitive inhibition of both oxytocin and vasopressin receptors, providing tocolytic effects with fewer maternal cardiovascular side effects compared to beta-mimetics like salbutamol and ritodrine 2, 3
- Clinical trials demonstrate that atosiban is as effective as beta-mimetics in delaying delivery for 48 hours (93.3% vs 95.0% for salbutamol) and 7 days (89.9% vs 90.1%) 2
- Tocolytic efficacy combined with tolerability (patients undelivered without requiring alternative tocolytic therapy) is significantly better with atosiban at 7 days (58.8% vs 46.3% compared to salbutamol, p=0.021) 2
Safety Profile
- Maternal cardiovascular side effects are substantially lower with atosiban compared to beta-mimetics (4.0% vs 84.3%, p<0.001) 3
- Treatment discontinuation due to maternal adverse events is significantly less common with atosiban (0.8%) compared to ritodrine (29.8%) 3
- The primary benefit of atosiban is its placebo-like maternal-fetal side effect profile while providing effective tocolysis 4
- Injection site reactions are more common with atosiban compared to placebo, but overall maternal-fetal adverse events are similar 4, 5
Clinical Applications
- The American College of Obstetricians and Gynecologists recommends tocolytic therapy primarily to delay delivery for 48-72 hours to allow for administration of antenatal corticosteroids and maternal transfer to tertiary care facilities 1
- Atosiban has demonstrated effectiveness in delaying preterm birth between 24-33 weeks of gestation, with evidence suggesting efficacy as early as 18-24 weeks of gestation 6
- Maintenance therapy with subcutaneous atosiban (30 μg/min) can prolong uterine quiescence after successful treatment of an acute episode of preterm labor (median time to recurrence: 32.6 days vs 27.6 days with placebo, p=0.02) 5
Limitations and Considerations
- Despite effectiveness in short-term delay of delivery, no tocolytic, including atosiban, has been consistently shown to improve overall neonatal outcomes or reduce the overall rate of preterm birth 1
- Caution is advised when using atosiban before 24 weeks of gestation, as limited data from one study suggested a higher incidence of fetal-infant deaths in this very early gestational age group 4
- The primary value of tocolysis with atosiban is to gain time for corticosteroid administration and maternal transfer to appropriate facilities 1
Comparison with Other Tocolytics
- When compared directly to beta-mimetics like salbutamol and ritodrine, atosiban shows similar efficacy but significantly fewer maternal side effects 2, 3
- The choice of tocolytic should consider gestational age, maternal comorbidities, and fetal status, with atosiban being particularly valuable when maternal cardiovascular side effects are a concern 1
- Neonatal outcomes appear similar between atosiban and other tocolytics, with morbidity related more to gestational age than to the specific tocolytic agent used 3