Pharmacokinetics of oral tapentadol in cats

Abstract To evaluate pharmacokinetics of one dose of tapentadol hydrochloride orally administered to cats. Prospective experimental study. Five healthy adult mixed‐breed cats. Each cat received 18.8 ± 1.0 mg/kg tapentadol orally. Venous blood samples were collected at time 0 (immediately prior to administration of tapentadol) 1, 2, 5, 10, 15, 30, 45, 60, 90 min, and 2, 4, 8, 12 to 24 h after drug administration. Plasma tapentadol concentrations and its metabolites were determined using ultra‐performance liquid chromatography–tandem mass spectrometry. Geometric mean Tmax of tapentadol, desmethyltapentadol, tapentadol‐O‐glucuronide, and tapentadol‐O‐sulfate was 2.3, 7.0, 6.0, and 4.6 h, respectively. Mean Cmax of tapentadol, desmethyltapentadol, tapentadol‐O‐glucuronide, and tapentadol‐O‐sulfate was 637, 66, 1134, and 15,757 ng/mL, respectively, after administration. Mean half‐life of tapentadol, desmethyltapentadol, tapentadol‐O‐glucuronide, and tapentadol‐O‐sulfate was 2.4, 4.7, 2.9, and 10.8 h. The relative exposure of tapentadol and its metabolites were tapentadol 2.65%, desmethyltapentadol 0.54%, tapentadol‐O‐glucuronide 6.22%, and tapentadol‐O‐sulfate 90.6%. Tapentadol‐O‐sulfate was the predominant metabolite following the administration of oral tapentadol in cats. Further studies are warranted to evaluate the association of analgesia with plasma concentrations of tapentadol.