Analgesic Efficacy and Safety of Hydromorphone in Chinchillas ( Chinchilla lanigera ).

Limited information is available regarding the efficacy of opioid analgesics in chinchillas. Here we sought to evaluate the analgesic efficacy and safety of hydromorphone in chinchillas. In a randomized, controlled, blind, complete crossover design, hydromorphone was administered at 0.5, 1, and 2 mg/kg SC to 16 chinchillas. Analgesic efficacy was determined by measuring hindlimb withdrawal latencies after a thermal noxious stimulus (Hargreaves method) at 0, 1, 2, 4, and 8 h after drug administration. Changes in daily food intake and fecal output after hydromorphone administration were recorded. At 2 mg/kg SC, but not at lower dosages, hydromorphone increased withdrawal latencies for less than 4 h. Food intake was reduced after all 3 dosages, and fecal output decreased in the 1- and 2-mg/kg groups. The decreases in these parameters were dose-dependent, with the greatest reduction measured over the first 24 h. Our current results indicate that hydromorphone at 2 mg/kg SC is an effective, short-acting analgesic drug in chinchillas that transiently reduces food intake and fecal output. Further studies are needed to evaluate the safety of hydromorphone in animals undergoing surgical procedures and general anesthesia and to determine whether lower doses provide analgesia in different nociceptive models.