... that can be completely reversed. It is commonly used for anesthesia of carnivores and primates. The rapid onset and short duration of anesthesia induced by the sedative-hypnotic propofol renders it particularly attractive for use in zoo species. However, due to the necessity for IV administration, its use is limited to species such as reptiles, birds, and small mammals that can safely be manually restrained for drug administration. It is also useful as an adjunct anesthetic agent in large mammals first immobilized with another drug combination. The potent opioids etorphine and carfentanil, alone or in combination with other agents (eg, acepromazine, xylazine, detomidine ), have been used extensively for anesthesia of ungulates, elephants, and rhinoceros. The antagonist of choice for etorphine or carfentanil is naltrexone, a pure narcotic antagonist, which induces complete reversal when given at 100 mg of naltrexone per mg of carfentanil or etorphine. The reversal dosage of naltrexone can be given IV or IM, and in species prone to renarcotization after reversal, additional naltrexone may be administered SC. It can also be given IM 6-8 ...