Evaluation of the Thermal Antinociceptive Effects of Buprenorphine Hydrochloride in American Kestrels (Falco sparverius)
Susanne M. Ceulemans2, BSc; David Sanchez-Migallon Guzman1, LV, MS, DECZM (Avian), DACZM; Glenn H. Olsen3, DVM, MS, PhD; Hugues Beaufrere4, DrMedVet, PhD, DABVP (Avian), DECZM (Avian); Joanne Paul-Murphy1, DVM, DACZM, DACAW
Recent studies have shown differences in the antinociceptive properties of opioid drugs in American kestrels.1,2 Hydromorphone, a pure mu-opioid agonist, had a dose responsive thermal antinociceptive effect suggestive of analgesic properties.1 In contrast, butorphanol, did not have a significant thermal antinociceptive effect at the dosages evaluated.2 The current study evaluated buprenorphine hydrochloride, known as a slow-onset, long-acting, partial mu agonist with poorly defined kappa receptor activity in American kestrels.3-7 A masked randomized complete crossover study using foot withdrawal threshold to a noxious thermal stimulus was performed to evaluate antinociceptive effects and duration of action of buprenorphine hydrochloride. Buprenorphine hydrochloride (0.1, 0.3 and 0.6 mg/kg IM, [Buprenex®, 0.3 mg/ml, Reckitt Benckiser Healthcare Ltd. Dansom Lane Hull, England]) and saline solution (0.9%NaCl, Hospira Inc., Lake Forest, IL, USA) were evaluated in 12 kestrels. Baseline thermal withdrawal threshold data were generated prior to drug administration followed by foot withdrawal threshold measurements at 0.5, 1.5, 3, and 6 hours after buprenorphine or saline administration. Kestrels were assigned an agitation-sedation score and monitored throughout the testing period for adverse effects. Buprenorphine hydrochloride caused a significant dose-dependent thermal antinociceptive response in American kestrels. The increase in mean withdrawal threshold was suggestive of analgesia. Further studies with other types of stimulations, formulations, dosages, and routes of administration in kestrels and other avian species are needed to fully evaluate the analgesic and adverse effects of buprenorphine and its clinical relevance.
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