Comparison of Different Formulations of Extended-Release Buprenorphine in Perioperative Pain Management in Common Marmosets (Callithrix jacchus)

Common marmosets (Callithrix jacchus) are increasingly used in biomedical research and often undergo surgery as part of IACUC-approved protocols. Therefore, pain control is essential to their clinical management and welfare. Extended-release buprenorphine is a valuable opioid analgesic option, as it can maintain plasma concentrations above therapeutic levels (0.1 ng/mL) for at least 72 h. However, no validated model is available to verify the analgesic effect of buprenorphine in marmosets. Therefore, this study compared the effects of buprenorphine-ER-LAB (Bup-ER-LAB) at 0.15 mg/kg and Ethiqa XR (EXR) at 0.15 and 0.1 mg/kg administered subcutaneously in marmosets undergoing surgical oocyte collection (n = 12 females) or vasectomy (n = 9 males). We hypothesized that these doses and formulations would provide similar analgesia during the 72-h postoperative period, determined with a marmoset composite measure pain scale designed for cage-side semiquantitative assessment of postoperative pain. The composite measure pain scale focused on animal appearance, activity, body posture/integument, respiration, surgical site, and social interactions, each with different subcategories and corresponding points to obtain a cumulative score. Animals were also assessed cage-side for locomotor activity and injection site reactions. No to minimal pain was scored, and no marmoset needed rescue analgesia. In total, 56% of the males and 25% of the females showed increased activity, which could last up to 48 h. Increased activity occurred in 57% of the BUP-ER-LAB group, 43% of the EXR 0.15 mg/kg group, and 14% of the EXR 0.1 mg/kg group (3 males and 4 females per group). Injection site reactions (erythema and/or swelling) occurred in 57% of the Bup-ER-LAB group, 29% of the EXR 0.15 mg/kg group, and 14% of the EXR 0.1 mg/kg group. Based on our results, we conclude that these formulations provide similar postoperative analgesia in marmosets, and an EXR dosage between 0.1 to 0.15 mg/kg provides adequate analgesia with less increase in activity and risk for injection site reaction.