First report on orally administered methadone to multi-drug resistance (MDR1) gene normal horses

Corrêa Natalini, CláudioCrosignani, NadiaLehn Linardi, Renata

Opioids are potent analgesics and are believed to be the best choice for moderate and severe nociceptive pain. Investigating all the possible administration route options for pain management in the different animal species is warranted in horses as systemic administration of these drugs in horses is difficult. In this study the authors describe for the first time in the literature the administration of methadone orally to MDR1 genotipically normal horses. Twelve adult healthy horses (6 females and 6 males) were studied. Horses randomly received one of the doses of methadone (0.1, 0.2, and 0.4mg/kg) per os, which was administered using a 60cc syringe containing 30ml of corn syrup The results showed all doses produced plasma levels compatible to analgesic plasma levels in human beings. The authors conclude that methadone is absorbed when orally administered in horses at doses of 0.1, 0.2, and 0.4 mg.kg -1. It does not produce excitement, sedation, nor undesirable side effects in healthy horses. Further studies are necessary in order to establish clinical guidelines for oral methadone as an alternative for pain management in the horse.

1. Farmacocinética
2. Metadona
3. Cavalos
4. MDR1