Pharmacokinetics of hydrocodone and hydromorphone after oral hydrocodone in healthy Greyhound dogs

The purpose of this study was to determine the pharmacokinetics of hydrocodone and its active metabolite hydromorphone in six healthy Greyhound dogs. Hydrocodone bitartrate was administered at a targeted dose of 0.5 mg/kg PO. Plasma concentrations of hydrocodone and hydromorphone were determined by liquid chromatography triple quadrupole mass spectrometry. The mean hydrocodone CMAX was 11.73 ng/mL at 0.74 h with a terminal half-life of 1.60 h. The mean hydromorphone CMAX was 5.2 ng/mL at 1.37 h with a terminal half-life of 3.07 h. Mean plasma hydromorphone concentrations exceeded 2 ng/mL from 0.5 to 8 h after hydrocodone administration. Further studies assessing the antinociceptive effects of oral hydrocodone are needed.