Randomized trial of two beta-mimetic drugs (ritodrine and fenoterol) in acute intra-partum tocolysis.

The uterine inhibitory effect and potential maternal and fetal side effects of two beta-mimetic compounds, ritodrine hydrochloride and fenoterol hydrobromide, were compared in a randomized trial. The drugs were administered by intravenous infusion to 24 healthy term nulliparous women during effective first-stage labour; each of them received fenoterol (1, 2, or 4 microgram/min) or ritodrine (100, 200, or 400 microgram/min). There was no difference between the drugs in the intensity of the uterine inhibition. However, for a similar inhibitory effect, the duration of tocolysis was longer after ritodrine. During the intrapartum and neonatal periods, neither compound induced any change in the fetal parameters investigated, and their effects on maternal parameters were comparable.