FRIDAY, Mar. 6 (HealthDay News) -- Pregnant women who are treated with tocolytics to postpone preterm labor may be at high risk of a serious adverse reaction to the drugs, according to research published online Mar. 5 in BMJ.

Roel de Heus, M.D., of the University Medical Centre in Utrecht, the Netherlands, and colleagues conducted a study of 1,920 women in 28 hospitals in the Netherlands and Belgium who were given tocolytics for prevention of preterm labor. Of these women, 41.9 percent received atosiban, 34.3 percent received nifedipine, 13.8 percent were treated with ritodrine and fenoterol and 8 percent were treated with indometacin, either singly, combined or in sequence.

Two of the drugs -- indometacin and atosiban -- were not associated with adverse drug reactions, but compared with atosiban, β adrenoceptor agonists had a relative risk of serious adverse drug reactions of 22.0 and calcium antagonists had a relative risk of 12.0, the investigators found. Among the 311 patients who received combination treatments, 1.6 percent of them experienced serious adverse drug reactions, the researchers report.

"An ideal tocolytic should postpone delivery at low costs without maternal and fetal side effects. None of the tocolytics described in this study fulfills these criteria. We found that combined treatment or a single treatment using β adrenoceptor agonists led to a higher incidence of serious adverse drug reactions, and such treatments should be discouraged," the authors write.

This study was funded by Ferring Pharmaceuticals BV, Hoofddorp, the Netherlands, which manufactures atosiban, and one of the co-authors received a grant from Ferring to perform a study on tocolysis.

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