Efficacy and safety of subcutaneous methadone hydrochloride in four-toed hedgehogs (Atelerix albiventris)

To evaluate the efficacy and safety of SC methadone in four-toed hedgehogs. 9 to 12 healthy adult four-toed hedgehogs (7 to 9 males and 3 females). Hedgehogs underwent 3 randomized, blinded, placebo-controlled, complete crossover studies. Hind limb withdrawal latencies in response to an acute thermal noxious stimulus were measured to evaluate the antinociceptive efficacy of methadone. Single doses of SC methadone were evaluated at 0.5 and 1 mg/kg for dose-dependent effects. Additionally, methadone (1.5 mg/kg) was administered at different concentrations to assess the effect of injection volume on antinociceptive efficacy. Finally, the safety of multiple doses of methadone (1.5 mg/kg, SC, q 2 h, for 3 doses) was also evaluated. In addition to monitoring behavior during latency measurements, animals were assessed for overt sedation. Food intake, body weight, and running wheel activity were assessed daily for 6 days following methadone administration to evaluate for adverse effects. Methadone at 1 and 1.5 mg/kg provided antinociception lasting < 2 hours, and injection volume had no significant effect on efficacy. Methadone at 0.5 mg/kg did not induce antinociception. Methadone produced transient abnormal behaviors in all hedgehogs, with more animals affected at the 1.5-mg/kg dose. Behaviors included periods of standing motionless, vocalization, chewing motions, and paw raising. Single- or multiple-dose administration of methadone had no significant effect on total food intake, body weight, or running wheel activity. The results of this study provide additional information on providing analgesia to hedgehogs. Subcutaneous methadone (1 to 1.5 mg/kg) can be used for short-term antinociception in hedgehogs.