Effect of cocaine administration on halothane MAC in dogs.

Intravenous cocaine (2 mg/kg or 4 mg/kg) was associated with a dose-dependent increase of halothane MAC in the dog. The largest increase in halothane MAC was from 1.06 plus or minus 0.03 to 1.35 plus or minus 0.04 vol/100 ml 3 hours after 4 mg/kg of cocaine. Halothane MAC 24 hours following a single administration of either 2 mg/kg or 4 mg/kg of cocaine or after 10 daily doses of 4 mg/kg of cocaine was near control MAC. These data support the speculation that increased central nervous system catecholamine concentrations, as may occur with cocaine, increase halothane anesthetic requirements.