TERBUTALINE INHIBITION OF MIDTRIMESTER UTERINE ACTIVITY INDUCED BY PROSTAGLANDIN F2αAND HYPERTONIC SALINE

Abstract

The effect of the beta receptor stimulator, terbutaline, on uterine activity induced by intra-amniotic injection of prostaglandin F2alpha or hypertonic saline was investigated in 20 patients undergoing therapeutic abortion in the second trimester. Intrauterine pressure was recorded, and the basal tone, intensity and frequency of contractions and "total" activity (expressed in Montevideo Units or MU), were measured. Uterine activity was higher in the prostaglandin group (mean value 393 MU) than in the hypertonic saline group (mean value 238 MU). However, terbutaline, infused at a rate of 5 to 20 mug/minute, decreased the activity by approximately the same absolute amount in the two groups to a mean value of 214 MU in the prostaglandin group and to 68 MU in the saline group. In some patients of the saline group, terbutaline completely inhibited uterine contractions. Basal tone, which was high in the prostaglandin group (mean value 28 mm Hg) decreased to a mean value of 17 mm Hg during terbutaline infusion. In the saline group the mean value for basal tone decreased from 10-5 to 7-5 mm Hg. It is concluded that uterine activity, induced by intra-amniotic injection of prostaglandin F2alpha or hypertonic saline, can be inhibited by terbutaline. The mechanisms of action for prostaglandins and hypertonic saline are discussed.