Abstract
Opioids are frequently used in veterinary medicine and are the most effective class of analgesic drugs for peri-operative pain. Previous studies have validated the clinical use of opioids for birds, particularly those substances with kappa (κ)-opioid receptor affinities.3,4,8,10 Butorphanol, a κ-opioid receptor agonist and mu (µ)-opioid receptor antagonist, is currently considered the opioid of choice for pain management in birds.3,4,8,10 However, butorphanol has a short plasma half-life in birds and is a controlled substance in the United States.9 Nalbuphine, an opioid that is not controlled by the DEA, has the same mechanism of action as butorphanol. Nalbuphine has been used to treat humans with acute and chronic pain,2,5-7 and has been shown to have anti-nociceptive effects in rats1. Preliminary data from analgesimetry studies suggest that nalbuphine also produces analgesia in Hispaniolan Amazon parrots (Guzman, unpubl. data). The pharmacokinetic profile of nalbuphine (12.5 mg/kg) following intramuscular (IM) or intravenous (IV) administration was determined using eight birds in a complete cross-over experimental design. Serum samples were collected at 5, 15, 30, 60, 90, 180, 360, and 540 minutes for the IM dose and at 1, 5, 15, 30, 60, 90, 180, and 360 minutes for the IV dose. Nalbuphine concentrations in plasma were determined by high performance liquid chromatography/tandem mass spectrometry (LC/MS/MS) and pharmacokinetic values were determined by using mean plasma nalbuphine concentrations at each time point. Data suggest that there is high nalbuphine bioavailability following IM administration, and that peak plasma concentration of nalbuphine is approximately 3 µg/ml. The elimination half-life following both IV and IM administration is less than 60 minutes, suggesting that frequent dosing may be required with nalbuphine.
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