Oxybutynin influence on autonomic measures in dogs

In the conscious dog, the most apparent oxybutynin effect was a dose-related tachycardia. Associated with this heart rate increase were a very slight, sometimes significant, elevation in diastolic pressure and an insignificant increase in systolic pressure. Under pentobarbital anesthesia, the systolic/diastolic arterial pressure oxybutynin responses were reversed and showed a dose-related systolic and diastolic hypotension. However, the tachycardic response to oxybutynin still appeared. The arterial pressure and heart rate responses produced by the autonomic agents were altered by the oxybutynin treatment in a pattern indicative of an anticholinergic mechanism of action. Differences in many response profiles were observed with either conscious or anesthetized dogs, but the statistically significant inhibition of the acetylcholine-induced systolic and diastolic arterial pressure and bradycardic responses were constant in both conditions. Oxybutynin is an anticholinergic agent with mild to moderate cardiovascular activity.