Enantioselective pharmacokinetics of racemic carprofen in New Zealand white rabbits.

The enantioselective pharmacokinetics of single dose (2 mg/kg) racemic carprofen (CPF) were evaluated in adult New Zealand white rabbits after intravenous (i.v.) and subcutaneous (s.c.) dose. Six rabbits were utilized in a two-way randomized crossover study and serial blood samples were collected. Plasma CPF concentrations were determined by high-performance liquid chromatography. After i.v. and s.c. racemic CPF administration, plasma concentration-time curves were best described by a two-compartment open model and a one-compartment model, respectively. The S(+) CPF enantiomer predominated in plasma following both routes of administration. Mean observed clearance of R(-)-CPF (82.17 +/- 13.70 mL/h.kg) was more rapid than for S(+)-CPF (27.92 +/- 7.07 mL/h.kg; P < 0.001). T(1/2)lambda z was shorter for R(-)-CPF than S(+)-CPF after both i.v. (1.03 and 2.99 h, respectively) and s.c. (1.94 and 4.14 h, respectively) dosing. Mean AUC(0-->infinity) ratios for R(-):S(+)-CPF were approximately 1:3 for both routes of administration. Mean residence time of R(-)-CPF was shorter than of S(+)-CPF (1.06 +/- 0.29 h, 3.45 +/- 0.50 h; P < 0.001) and R(-)- and S(+)-CPF volumes of distribution at steady state were 85.00 +/- 14.42 and 94.39 +/- 18.66 mL/kg, respectively after i.v. administration. The mean s.c. bioavailability [F (%)] for both R(-)- and S(+)-CPF was high, 94.4 +/- 22.8 and 91.0 +/- 35.7%, respectively.