Effect of injection site on dexmedetomidine-ketamine induced sedation in leopard geckos (Eublepharis macularius)

OBJECTIVE To evaluate whether the sedative effects of a combination of dexmedetomidine and ketamine differed when it was administered IM in a hind limb versus a forelimb of leopard geckos (Eublepharis macularius). DESIGN Randomized crossover study. ANIMALS 9 healthy adult leopard geckos. PROCEDURES Each gecko received a combination of dexmedetomidine (0.1 mg/kg [0.045 mg/lb]) and ketamine (10 mg/kg [4.5 mg/lb]; DK), IM, in a forelimb and hind limb in a randomized order and with a 7-day interval between treatments. All geckos received atipamezole (1 mg/kg [0.45 mg/lb], SC) 45 minutes after DK administration. Palpebral and righting reflexes, jaw tone, and superficial pain and escape responses were each assessed on a 3-point scale, and the scores for those variables were summed to calculate a sedation score. Those variables and heart and respiratory rates were evaluated at predetermined times before and for 1 hour after DK administration. RESULTS For the forelimb treatment, mean sedation score was higher and mean heart rate was lower than the corresponding values for the hind limb treatment at most time points after DK administration. The righting reflex remained intact for all 9 geckos following the hind limb treatment but became absent in 7 geckos following the forelimb treatment. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the extent of DK-induced sedation was greater when the combination was injected IM in a forelimb versus a hind limb of leopard geckos, likely owing to a hepatic first-pass effect following hind limb injection. In reptiles, IM hind limb administration of drugs that undergo hepatic metabolism and excretion is not recommended.