Pharmacokinetics of a Concentrated Buprenorphine Formulation in Red-Tailed Hawks (Buteo jamaicensis)
Opioid drugs are the cornerstone therapy for moderate to severe pain management, and recent studies have shown mu opioid agonists to be effective in some raptor species.1-3 The pharmacokinetics of two doses of a concentrated formulation of buprenorphine (Simbadol™, 0.3 mg/kg SC)a were evaluated in red-tailed hawks (Buteo jamaicensis, n=6). Blood samples were collected at 10 timepoints over a 24-hour period after drug administration to determine buprenorphine plasma concentrations using liquid chromatography-tandem mass spectrometry. After a 4-week washout period, the same birds were administered 1.8 mg/kg SC of the same formulation. Blood samples were collected at 13 timepoints over a 96-hour period after drug administration. The hawks were monitored for adverse effects and assigned a sedation/agitation score at each timepoint. Maximum buprenorphine concentration was achieved at 5 and 15 minutes for the 0.3 mg/kg and 1.8 mg/kg doses, and plasma concentrations were maintained above 1 ng/ml for at least 24 and 48 hours, respectively. The elimination half-life was 7.12 and 8.74 hours for the low and high doses. There were significantly higher sedation scores for both doses (p<0.001) at the timepoints evaluated between 15 minutes and 48 hours. No adverse effects were noted in any birds. In summary, the formulation evaluated results in rapid absorption of buprenorphine and plasma concentrations above 1 ng/ml for 24 and 48 hours following administration of 0.3 and 1.8 mg/kg SC, respectively, causing mild to moderate sedation in red-tailed hawks.
a. Simbadol™ 1.8 mg/ml buprenorphine, Zoetis, Parsippany, NJ, USA
The authors would like to thank the California Raptor Center for their dedicated care of the hawks used in this study and assistance with data collection.
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