Atosiban

Atosiban (Tractocile® or Antocin®, RWJ 22164) is an inhibitor of the hormones oxytocin and vasopressin, and is used intravenously in premature labor. Although initial studies suggested it could be used as a nasal spray and hence would not require hospital admission, it is not used in that form. It was developed by Ferring Pharmaceuticals in Sweden and first reported in the literature in 1985.

Chemically, it is a modified form of oxytocin that inhibits the action of this hormone on the uterus, leading to a cessation of contractions. It is therefore a tocolytic.

A 2005 systematic review by the Cochrane Collaboration showed that while atosiban had less side-effects than alternative drugs (such as ritodrine), it was no better than placebo in the major outcomes, and in one study showed worse neonatal outcomes. The reviewers suggest nifedipine may be more promising.