Dosage Trials Using Medetomidine as an Oral Preanesthetic Agent in Chimpanzees (Pan troglodytes)
Karen S. Kearns1, DVM; Josephine Afema2, BVM; Ann Duncan3, DVM
Current techniques for restraint of chimpanzees (Pan troglodytes) require the use of remote injection delivery systems. This method can be difficult to execute on an intelligent, moving target, and it is inherently stressful to the animals and personnel involved. This study was undertaken to determine if medetomidine (Domitor, Pfizer, Exton, PA, USA) could be effectively used as an oral preanesthetic agent for chimpanzees immobilized with ketamine (Ketaset, Fort Dodge Laboratories, Inc., Fort Dodge, IA, USA). The study involved 14 animals at the Uganda Wildlife Education Centre (UWEC), two animals at the Detroit Zoo, and one animal at the Knoxville Zoo. Nine animals received 50–100 g/kg of medetomidine orally in marshmallow creme prior to immobilization by ketamine injection. A control group of eight animals received medetomidine with ketamine as a single intramuscular injection. Reversal of the medetomidine was performed at the end of the procedure, using 200 g/kg atipamezole (Antisedan, Pfizer, Exton, PA, USA). Animals who received oral medetomidine were monitored for depth of sedation every 5 minutes for 30 minutes prior to ketamine injection. Preliminary findings showed that chimps at UWEC receiving 75 g/kg medetomidine orally were noticeably sedate after 30 minutes. These chimps would move more slowly, lie down more, and sometimes close their eyes. None became completely immobilized by the premedicant alone. Increasing the dose to 100 g/kg did not show a noticeable increase in depth of sedation. The three chimps from U.S. zoos who received oral medetomidine showed little to no visible sedation, even at the 100 g/kg dosage. While the chimps from U.S. zoos had become accustomed throughout their lives to a yearly routine of fasting followed by a stressful encounter with a blowpipe, many of the UWEC chimps were young and had not required previous immobilization; only a few were adults with previous experience with blowdarting. It appears that medetomidine can be used as an effective oral premedicant in chimpanzees if the individual animals are not already stressed before the drug is administered.
This study was supported by a grant from the Columbus Zoo Conservation Fund. The authors would like to thank the staff of the Uganda Wildlife Education Centre, the Detroit Zoo, and the Knoxville Zoo for their assistance with this project.