Abstract
A mother–daughter pair of black and white colobus monkeys (Colobus guereza) aged 17 and 14 yr, respectively, at the Topeka Zoological Park were immobilized for annual examinations and dental work. Butorphanol tartrate (Fort Dodge 10 mg/ml) was given intramuscularly at a dose of 0.2 mg/kg for pain caused by tooth extraction. Both animals became apneic. The first animal was ventilated until spontaneous respiration had resumed. The second was induced to resume respiring by administration of naltrexone HCl to antagonize the butorphanol.
Case Report
On 6 October 1997, two black and white colobus monkeys were immobilized for physical examination and dental work with 75 and 50 mg Telazol (tiletamine HCl-zolazepam HCl, Fort Dodge Laboratories, Inc. Fort Dodge, Iowa, USA)1,2, respectively. They were transported to the Animal Health Center, intubated and maintained on isoflurane gas anesthesia (Iso Flo, Abbott Laboratories, North Chicago, Illinois, USA). Blood was drawn from the femoral vein for CBC, chemistry panel and serum banking. Whole body and skull radiographs were taken. Treatments in addition to the Telazol included Baytril (Bayer Corporation, Shawnee Mission, Kansas, USA). 4.3 mg/kg, palpebral tuberculosis testing with mammalian tuberculin (Human Isolates Intradermic Coopers Animal Health, Inc., Kansas City, Kansas, USA) 0.1 ml intradermally and Torbugesic (butorphanol tartrate, Fort Dodge Laboratories, Inc. Fort Dodge, Iowa, USA; 10 mg/ml) 0.2 mg/kg i.m.1
Both animals have had a history of dental disease of unknown origin. They have both had multiple extractions in the past. The older animal required all of its remaining teeth to be pulled. The younger was left with five teeth. The daughter was immobilized first. The animal was immobilized with 75 mg Telazol i.m., transported to the zoo’s hospital, intubated and maintained on isoflurane. Additional treatments included 35 mg Baytril, 1.4 mg butorphanol, and a tuberculin test. During the procedure, the animal stopped breathing. Intermittent positive pressure ventilation was initiated and the isoflurane flow rate was decreased and then stopped, maintaining the animal on oxygen alone. The animal was treated numerous times with Dopram (Fort Dodge), soon after which it would take a few breaths and then stop. Even presumed pain would not induce the animal to breathe as there was no respiration associated with the extraction of teeth. The heart rate continued to be stable despite the continued apnea. The procedure was completed, yet the animal was still not breathing on its own. IPPV was continued. At one point approximately 2.5 hr later, mucus membranes turned gray, pupils dilated, and the animal appeared to being dying. IPPV was increased to a rapid rate, more Dopram was given and the animal suddenly began breathing and rapidly returned to a normal, stable plane. From that point on, the animal seemed fine. Mucus membrane color became pink and CRT improved to less than 2 sec.
Before sedating the second animal, a quick literature search revealed that Telazol can have some depressive effects on respiration. These effects were mainly post induction apnea and were transient but could be treated, if necessary, with 5.5 mg/kg Dopram.3 The decision was made to continue with the second procedure in the hope that the previous incident was an individual idiosyncrasy with regards to the Telazol as both of these animals had been sedated with Telazol in the past.
The second procedure was identical to the first except for a reduced Telazol dose of 50 mg in case the previous apnea had been due to Telazol. Throughout the induction and the initial procedure, the animal continued to breathe normally. Breathing continued normally until the point of giving the additional medications which included 34 mg Baytril, 800 mg Pipracillin (Pipracil, Abbott Laboratories), 1.5 mg butorphanol, and the tuberculin test. Within 1 min, the animal also stopped breathing. Dopram was given and just like the first animal, this animal would take one breath immediately after the administration, then go apneic again. At this point the assumption was made that it was not the Telazol that was causing the apnea but the butorphanol. The animal was treated with 25 mg naltrexone to reverse the effects of the butorphanol. Within a few minutes it resumed breathing and respiratory rate remained normal for the duration of the procedure.
Conclusion
The reversal of the apnea after administration of naltrexone suggests that the butorphanol was the culprit. Other drug combinations such as Telazol followed by isoflurane can probably be ruled out because of the timing involved when the apnea occurred. Butorphanol, on a weight basis, is four to seven times as potent of an analgesic as morphine. Its analgesic action occurs at sites in the limbic system. Overdosage may cause respiratory depression and should be treated with Naloxone and appropriate supportive therapy.3 A chance for overdosage with this particular product includes mistaking the 10 mg/ml product for the 0.5 mg/ml. Having only one size on hand will eliminate that possible error. I have used butorphanol successfully in other primates at the same published doses. These two individuals may have a genetically related sensitivity to the drug. Whether or not it is dose related is unknown as it has not been used again on these animals.
Literature Cited
1. Carpenter, J.W., T.Y. Mashima, and D.J. Rupiper. 1996. Exotic Animal Formulary, 1st ed. Greystone Publications, Manhattan, Kansas.
2. Lumb, W.V. and E.W. Jones. 1996. Veterinary Anesthesia, 3rd ed. Williams and Wilkins, Baltimore, Maryland.
3. Plumb, D.C.1995. Veterinary Drug Handbook, 2nd ed. Pharma Vet Publishing, White Bear Lake, Minnesota.