DETERMINATION OF PLASMA CONCENTRATION OF (-) CLAUSENAMIDE AND 6-HYDROXYL-CLAUSENAMIDE IN RATS BY HPLC AND THEIR PHARMACOKINETICS

AIM　To Determine the concentration of (-) clausenamide［(-)clau］ and its essential metabolite─6-Hydroxyl- clausenamide(6-OH-clau) in rat plasma and study their pharmacokinetics.METHODS　A reversed-phase high performance liquid chromatography with ultraviolet detection has been developed for determination of (-)clau and its metabolites in rat plasma using a column of Kromasil C₁₈(5 μm) and mobile phase of acetonitrile-methanol-water(21∶16.5∶62.5). DM-9384 was used as an internal standard. Rat plasma samples were extracted with chloroform. RESULTS　The mean relative recovery of (-)clau was 100.9%±4.4%(n=3) with within-day precision of 1.8%～6.2% and between-day precision of 1.06%～3.31%, and the limit of detection was 24 ng.mL^-1. At the range of 0.47～968 μg.mL^-1 for (-)clau, and 0.049～200 μg.mL^-1 for 6-OH-clau, there was a linear relationship with a value for γ=0.999. By the nonlinear least-squares regression and F test between different compartments using a computer program 3P87, the plasma concentration vs time course of (-) clau given iv 80 mg.kg^-1 to rats was found to fit a 2-compartments open model. The following pharmacokinetic parameters were obtained: for (-)clau, T_1/2α=(12.19±1.68) min, Vd=(1.19±0.31)　L.kg^-1, T_1/2β=(156.65±18.65)　min and AUC0～720=(1286.09±171.56)　min.μg.L^-1; for 6-OH(-)clau, T_1/2Kt=(9.61±3.56)　min,　T_1/2β=(238.81±48.66)　min, Tmax=(17.91±3.05)　min, Cmax=(1.29±0.11) μg*mL^-1 and AUC_0～480=(78.31±5.35)　min.μg.L^-1. CONCLUSION　(-)Clau exhibited a pharmacokinetic character that its distribution, transformation and elimination in rat plasma are all relatively rapid.