Pain management in avian patients (Proceedings)


Pain management in avian patients (Proceedings)

Aug 01, 2008

When one speaks of pain management in dogs they are discussing one species with research to back up their statements. Did you realize there are over 8000 species of birds? Even if we limit our discussion to the order Psittaciformes (parrots), that includes 353 different species and subspecies that are as diverse as a parakeet at 30 grams and a blue and gold macaw at 1000 grams. Not only are they different in size, but some parrots are from the rain forest and some are from the desert, some are New World species (from South America for example) and others are Old World species (from Australia or Africa for example). In addition, it is known that different species of psittacine birds metabolize several drugs differently than other psittacine birds. For example, macaws often regurgitate on "regular" avian doses of trimethoprim-sulfa, and African grey parrots often become profoundly depressed on "regular" avian doses of itraconazole. Another example is Old World Gyps Vultures developing visceral gout, renal necrosis and death a few days after exposure to small doses of diclofenac, an NSAID, (median lethal dose in this species is 0.1 – 0.2 mg/kg; low enough to be exposed to lethal doses by ingesting tissues of cattle given the drug), whereas turkey vultures receiving doses of up to 25 mg/kg had no ill effects recognized either clinically or histologically. This has led to the recent ban by the Indian, Nepali, and Pakistan governments on the use of diclofenac in cattle. Recent pharmacokinetic studies in several species of Gyps vultures showed meloxicam, another NSAID, to be safe for use. There are probably many unknowns in regards to the metablolism or action of pain relieving drugs in the many species of psittacine birds, or just even in the 10 most commonly kept psittacine species in captivity. Therefore, when assessing an avian patient for signs of pain, or deciding on which pain reliever to use, or what dose and how often to administer, it must be taken into account that there is NO GENERIC PARROT, and one must be familiar with the very limited scientific research that has been conducted regarding pain management in psittacine birds. Also, each patient must be evaluated and re-evaluated individually and constantly.

What research has been done in psittacine birds and what is known?

Most recent studies in psittacine birds have been performed by Dr. Joanne Paul-Murphy and her colleagues at the University of Wisconsin. They have shown the following:

1994 – butorphanol at 1.0 mg/kg IM had an isoflurane-sparing effect in cockatoos (11 of 3 different species of cockatoo)

1999 – developed a model for assessing analgesic effects in birds using a perch that was half electrified and half thermal; 31 African grey parrots (2 sub-species) lifted a foot or flinched their wings in response to a stimulus; the response to the thermal stimulus was variable, but the response to the electrified perch was predictable

1999 – using the above electrified perch model, 29 African grey parrots (2 sub-species) had a significantly increased threshold value after administration of butorphanol at 1.0 mg/kg IM, but not with buprenorphine at 0.1 mg/kg IM

2004 – pharmacokinetic (PK) study of buprenorphine at 0.1 mg/kg IM given once achieved plasma concentrations that would be analgesic in humans (0.5-1.0 ng/ml) for 2 hours, but the authors recommended that further PK and analgesic studies be performed with higher doses before using this dose

2006 – PK and analgesic study using the above model in 11 Hispaniolan Amazon parrots showed that liposomal encapsulated butorphanol tartarate (LEBT) (15 mg/kg SQ) had plasma levels and analgesic effects lasting 3-5 days compared to standard butorphanol tartarate (STDBT) (5 mg/kg IM) lasting less than 24 hours; unfortunately LEBT is not yet available commercially

Formulary doses and references (from Carpenter's formulary):
Future work may involve evaluating the percentage of types of opiate receptors in birds. It is thought that birds possess more kappa than mu opiate receptors.

In my experience, tramadol (an opiate) at 4 mg/kg orally once or twice daily worked well long term in a parrotlet with debilitating gout (since there were renal issues, an NSAID was not the best choice). Since that first bird, we have used tramadol in several other species and studies are currently being conducted.