ANTINOCICEPTIVE EFFICACY AND SAFETY OF SUBCUTANEOUS TRAMADOL IN CHINCHILLAS (CHINCHILLA LANIGERA)

Abstract

Tramadol has been demonstrated to provide analgesia in rats and mice and has been increasingly used in other small companion mammals for treatment of moderate to severe pain. Currently no evidence is available that supports the use of tramadol as an effective analgesic in chinchillas. The purpose of this study was to evaluate the antinociceptive efficacy and safety of subcutaneously administered tramadol in chinchillas. Initial dose-escalation studies were performed to determine if dose-dependent adverse effects occur in chinchillas. At 60 mg/kg subcutaneously (SC), but not at lower doses, tramadol induced clinically significant dose-limiting adverse effects, consisting of whole body tremors and facial muscle fasciculation. Therefore, in a subsequent analgesimetry experiment, tramadol was evaluated at a single dose of 10, 20, and 40 mg/kg SC in a randomized, blinded, controlled, complete crossover design. Thermal antinociceptive efficacy was determined by measuring hindlimb withdrawal latencies following a thermal noxious stimulus (Hargreaves’ method) at 0, 1, 2, 4, and 8 hours after drug administration. Changes in daily food intake and fecal output following tramadol administration were measured. At 10 to 40 mg/kg SC no thermal antinociceptive effects could be demonstrated. A self-limiting and transient significant reduction in food intake and fecal output occurred in a dose-dependent manner when tramadol was administered at 20 and 40 mg/kg. Based on the results of this study tramadol cannot be recommended as an analgesic drug in chinchillas.