Pharmacokinetics of a Single Subcutaneous Dose of Sustained Release Buprenorphine in Northern Elephant Seals (Mirounga angustirostris)
Sustained-release buprenorphine represents a novel method to improve animal health by providing a potentially long-lasting analgesic up to 72 hours. This study aimed to establish the pharmacokinetic parameters of a single subcutaneous dose of sustained-release buprenorphine in a population of healthy juvenile northern elephant seals (Mirounga angustirostris), evaluate for adverse clinical effects, and compare plasma concentrations achieved to known therapeutic concentrations in other species. A single dose of sustained-release buprenorphine (Buprenorphine-SR®, Zoo Pharm, Windsor, CO, USA, 10 mg/mL) at 0.12 mg/kg was administered subcutaneously over the right caudal pelvis in healthy juvenile northern elephant seals (n = 26). Blood samples were collected from the dorsal intervertebral sinus at 0 hours and at 3 or 4 of the following time points: 0.5, 1, 2, 6, 12, 24, 36, 48, 60, 96, 120, and 144 hours. Seals were examined daily for systemic and local injection-site adverse reactions. Plasma was analyzed by mass spectrometry for buprenorphine and norbuprenorphine concentration. A non-compartmental analysis for pharmacokinetic parameters was calculated using standard methods and equations. The average maximum concentration of 1.21 ng/mL was detected 12 hours post-drug administration. Quantifiable plasma concentrations were observed up to 144 hours post-administration, but at concentrations less than 1.0 ng/mL after 24 hours. Firm swellings or abscesses were observed at the injection site in 6 (23.1%) seals between 24–168 hours post-administration, suggesting that this drug should be used with caution in northern elephant seals.
The authors wish to thank the Sacramento Zoo Conservation Fund, the Oiled Wildlife Care Network, and Zoo Pharm for their support of this project. Additionally, the authors would like to acknowledge the dedication and contributions of The Marine Mammal Center staff and volunteers.
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