Clinical manifestations of overdose of ketamine-xylazine in the cat.

10 cats were anesthetized with high doses of Ketamine/Xylazine combination (50 mg/kg and 6 mg per cat respectively). 10 other cats were given Ketamine alone (100 mg/kg). The drugs were given i/m. Heart rate and respiratory rate were measured with regular intervals for 3 hours and certain reflexes were checked in the same period. Blood parameters (pH, pO2, pCO2) from arterial blood, were studied 10--15 min. after application. The values measured after application of these high doses never reached critical levels and no clinical signs of cyanosis were observed. Physostigmine has been reported to have an antagonistic effect on Ketamine in humans, but this could not be demonstrated in cats. The increase of dose levels did not improve or lengthen the anaesthetic effect of the drugs, but the period of recovery was highly extended. There were no clinical signs of acute toxicity and it is concluded that even severe misjudgements of the bodyweight should not lead to fatal results.