Papers of the Week

Tapentadol is an analgesic agent that acts as both a µ-opioid receptor agonist and a norepinephrine reuptake inhibitor. It is a common therapeutic agent in human medicine for management of acute and chronic pain, and it is currently being investigated for use in veterinary medicine. Tapentadol was evaluated in Hispaniolan Amazon parrots () because there is only 1 other oral opioid-like analgesic agent, tramadol, which has been evaluated in an avian species. The effectiveness of tramadol after administration to a patient involves a complex physiologic metabolism and has been found to have variable pharmacokinetics between species. Because of the lack of active metabolites from tapentadol, less interspecific variation was expected. Seven Hispaniolan Amazon parrots were used to evaluate the pharmacokinetics of tapentadol after a single 30 mg/kg PO administration of a compounded 5 mg/mL tapentadol suspension. Blood samples were collected before (time 0) and 0.25, 0.5, 0.75, 1, 1.5, 3, and 6 hours after administration, following a balanced, incomplete-block design. Plasma tapentadol concentrations were measured by high-pressure liquid chromatography with mass spectrometry. Results revealed detectable plasma concentrations in only 2 of 7 birds (29%), and the bird with the highest plasma levels had a peak concentration () of 143 ng/mL and a half-life () of 24.8 minutes. The variable plasma concentrations and short half-life of this drug in Hispaniolan Amazon parrots suggests that this drug would be of limited clinical use in this species; however, it is possible that this drug will be more bioavailable in other avian species.