The oxytocic effect of xylazine on the canine uterus

The effect of xylazine on intrauterine pressure was compared to that of prostaglandin and oxytocin in seven diestrual bitches. Microtipped pressure transducers were surgically implanted in the uteri of four bitches at 30 d diestrus and in three bitches at 60 d diestrus. Uterine contractile force was measured in the awake bitches on Day 1 and Day 2 following implantation. Uterine responses to intravenous prostaglandin (5 mug/kg), oxytocin (0.05 USP units/kg), and xylazine (0.22 mg/kg) were measured. In the 30-d diestrual bitches, prostaglandin and oxytocin increased intrauterine pressure to 67 and 69 mmHg, with the duration of action being 16 and 14 min, respectively. Xylazine increased intra-uterine pressure to 49 mmHg and had a duration of action of 8 min. All results were decreased but similar in the 60-d diestrual bitches. These findings indicate that xylazine, given intravenously, produces a transitory increase in intrauterine pressure in the diestrual bitch.