Evaluation of the thermal antinociceptive effects of hydromorphone hydrochloride after intramuscular administration to orange-winged Amazon parrots (Amazona amazonica).

OBJECTIVE

To evaluate the thermal antinociceptive effects of hydromorphone hydrochloride after IM administration to orange-winged Amazon parrots (Amazona amazonica).

ANIMALS: 8 healthy adult parrots (4 males and 4 females).

PROCEDURES: In a randomized crossover study, each bird received hydromorphone (0.1, 1, and 2 mg/kg) and saline (0.9% NaCl) solution (1 mL/kg; control) IM, with a 7-day interval between treatments. Each bird was assigned an agitation-sedation score, and the thermal foot withdrawal threshold (TFWT) was measured at predetermined times before and after treatment administration. Adverse effects were also monitored. The TFWT, agitation-sedation score, and proportion of birds that developed adverse effects were compared among treatments over time.

RESULTS

Compared with the mean TFWT for the control treatment, the mean TFWT was significantly increased at 0.5, 1.5, and 3 hours and 1.5, 3, and 6 hours after administration of the 1- and 2-mg/kg hydromorphone doses, respectively. Significant agitation was observed at 0.5, 1.5, and 3 hours after administration of the 1 - and 2-mg/kg hydromorphone doses. Other adverse effects observed after administration of the 1- and 2-mg/kg doses included miosis, ataxia, and nausea-like behavior (opening the beak and moving the tongue back and forth).

CONCLUSIONS AND CLINICAL RELEVANCE: Although the 1- and 2-mg/kg hydromorphone doses appeared to have antinociceptive effects, they also caused agitation, signs of nausea, and ataxia. Further research is necessary to evaluate administration of lower doses of hydromorphone and other types of stimulation to better elucidate the analgesic and adverse effects of the drug in psittacine species.