Pharmacokinetics of Oxymorphone in Titi Monkeys (Callicebus spp.) and Rhesus Macaques (Macaca mulatta)

Oxymorphone is a pure p.-opioid receptor agonist that is commonly used in nonhuman primate medicine and surgery to minimize pain ranging in intensity from moderate to severe. We compared pharmacokinetic profiles and physiologic and behavioral responses to oxymorphone between titi monkeys (Callicebus spp.) and rhesus macaques (Macaca mulatta). Titi monkeys (n = 4) and rhesus macaques (n = 4) were injected intravenously with either a bolus of 0.075 mg/kg oxymorphone or placebo on multiple occasions, with a minimal washout period of 14 d between trials. Blood collection was limited to no more than 3 samples per trial, with samples collected at multiple time points until 10 h after injection. Collection periods, animal order, and testing day were randomized. In addition, macaques underwent a single serial collection at all time points to validate study design. A 2-compartment model best described the disposition of oxymorphone in both species. Clearance was faster in macaques than titi monkeys, in which terminal half-life was longer. Statistically significant physiologic differences were found between species and between treatments within species. Apart from these effects, oxymorphone did not significantly change physiologic parameters over time. After oxymorphone treatment, macaques demonstrated behaviors reflecting pruritis, whereas titi monkeys exhibited sedation. Despite its mild side effects, we recommend the consideration of oxymorphone for pain management protocols in both Old and New World nonhuman primates.