Pharmacokinetics of buprenorphine following intravenous and intramuscular administration in male rhesus macaques (Macaca mulatta )

This study reports the pharmacokinetics of buprenorphine in conscious rhesus macaques (Macaca mulatta) after intravenous (IV) and intramuscular (IM) administration. Four healthy, opioid-naïve, socially-housed, adult male macaques were used. Buprenorphine (0.03 mg/kg) was administered intravenously as a bolus or intramuscularly on separate occasions. Blood samples were collected prior to, and up to 24 h, post-administration. Serum buprenorphine concentrations were analyzed with liquid chromatography-mass spectrometry. Noncompartmental pharmacokinetic analysis was performed with commercially available software. Mean residence time in the IV study as compared to the IM study was 177 (159–189) minutes vs. 185 (174–214) minutes, respectively [median (range)]. In the IV study, concentration back extrapolated to time zero was found to be 33.0 (16.8–57.0) ng/mL [median (range)]. On the other hand, the maximum serum concentration found in the IM study was 11.8 (6.30–14.8) ng/mL [median (range)]. Rhesus macaques maintained concentrations greater than 0.10 ng/mL for over 24 h in the IV study and over 12 h in the IM study. Bioavailability was found to be 68.1 (59.3–71.2)% [median (range)]. No significant adverse effects were observed in the monkeys at the 0.03 mg/kg dose of buprenorphine during either study.