INHIBITION OF XYLAZINE INDUCED UTERINE CONTRACTILITY BY CLENBUTEROL AND NIFEDIPINE

A study was undertaken in order to determine the effects of xylazine o n uterine contractility in goats premedicated with clenbuterol or nife dipine. These drugs inhibit uterine activity by acting as potent tocol ytic or uterine relaxant agents. A balloon-tipped catheter was inserte d under sedation and local anaesthesia on to a uterine horn in 15 cycl ing goats in order to record intrauterine pressure changes. Three grou ps of five goats were used: group I was treated with an intravenous do se of 0.1 mg kg(-1) of xylazine. Groups II and III were pretreated wit h 4 mu g kg(-1) of clenbuterol and 80 mu g kg(-1) of nifedipine, respe ctively, before administrating the same dose of xylazine. Xylazine inc reased the frequency and intensity of uterine contractions significant ly and the value of the area under the contraction curves was signific antly higher than that observed under basal conditions i.e. before dru g treatment. In goats premedicated with clenbuterol or nifedipine, the uterotonic effects of xylazine (2858+/-217 versus basal contractility : 1241+/-173 mm(2).5 min(-1), P <0.05) were inhibited for the 30 minut es recording period. These data indicate that clenbuterol and nifedipi ne can be used as potent tocolytic agents in order to prevent the uter ine side effects of xylazine.