Effects of terbutaline on human uterine motility at term.
The effects of the selective beta-2-receptor stimulator terbutaline on the activity of gravid, human myometrium were investigated in vitro and in vivo, before and after administration of different beta-receptor blockers. Terbutaline, 0.2-1.0 mu-g/ml, inhibited the spontaneous contractile activity of isolated strips of myometrium. This effect was unaffected by the selective beta-a-receptor blockers practolol, 1 mu-g/ml, and H 93/26, 1 mu-g/ml. However, the non-selective blocker propranolol, 0.1 mu-g/ml, completely inhibited the terbutaline effects. The in vitro effects of terbutaline could be correlated with findings in vivo. Intra-uterine pressure was recorded in 4 pregnant women at term. Infusion of terbutaline, 10-15 mu-g/min, for 20-40 min, effectively inhibited both spontaneous and oxytocin-stimulated uterine activity. There was a moderate increase in maternal heart rate, but no consistent effect on maternal blood pressure. Fetal heart rate was little affected. The uterine effects of terbuline were not influenced by practolol, 5-20 mg i.v., but completely inhibited by propranolol, 1-2 mg i.v. The results suggest that terbutaline inhibits uterine motility by effects on uterine beta-2-receptors and that it can be given in clinically effective doses without adverse circulatory effects on mother or fetus.
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D003864:Depression, Chemical; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D010121:Oxytocin / Q000494:pharmacology; D011217:Practolol / Q000494:pharmacology; D011247:Pregnancy; D011433:Propranolol / Q000494:pharmacology; D013726:Terbutaline / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects*
D010121:Oxytocin; D011433:Propranolol; D013726:Terbutaline; D011217:Practolol