Pharmacokinetics of the novel atypical opioid tapentadol after intravenous, intramuscular and subcutaneous administration in cats

Drugs that provide effective analgesia in cats are limited. The aim of the present study was to investigate the pharmacokinetics of the novel atypical drug tapentadol (TAP) after intravenous (IV), intramuscular (IM) and subcutaneous (SC) injection in six healthy cats using a 3 × 3 Latin square crossover study design. The dose rate used was 5 mg/kg and the concentrations of TAP in plasma were evaluated using high-performance liquid chromatography.Some adverse effects including salivation, agitation and panting, were noted, especially following IV administration. In all three administration groups, TAP concentrations were detectable in plasma for up to 8 h. Bioavailability for each route was almost complete, accounting for 94% and 90% after IM and SC administrations, respectively. Drug absorption was faster after IM than SC administration (0.25 h vs. 0.63 h). The half-life of the terminal portion of the plasma concentration curve was not significantly different between the three routes of administrations (2-3 h). TAP appears to have some variation in its pharmacokinetic features in cats compared to other animal species. Further studies are needed to evaluate whether TAP would be suitable for use in cats that are experiencing moderate to severe pain, but are sensitive to the adverse effects of commonly prescribed opioids.