Muscle necrosis in Syrian hamsters resulting from intramuscular injections of ketamine and xylazine.

To assess tissue damage resulting from intramuscular injection of mixtures of ketamine and xylazine, 48 hamsters were given 100, 150 or 200 mg/kg ketamine and 10 mg/kg xylazine in one hind leg and an equal volume of sterile physiologic saline in the other leg. Four hamsters from each group were killed 1, 3, 7 and 14 days after injection and the tissues at the injection sites were examined. There was grossly apparent muscle necrosis in most of the ketamine-xylazine injected legs. By light microscopy, 47 of 48 legs injected with ketamine-xylazine had moderate to extensive muscle necrosis with an acute to chronic inflammatory response, depending on the time elapsed since injection. Microscopic slides of the injection sites were coded, randomized and scored for severity of muscle lesions. Lesion scores for ketamine-xylazine injected legs were significantly higher than controls at all post-injection times. These findings indicate that intramuscular injection of ketamine with xylazine can cause extensive muscle necrosis in hamsters and should not be used for anesthesia in survival procedures.