Steady-state kinetics of bezafibrate and clofibrate in healthy female volunteers

The steady-state kinetics of chlorophenoxyisobuytric acid (CPIB) and of bezafibrate were investigated in a strictly controlled, randomised cross-over study in 10 female volunteers, after the conventional oral doses of clofibrate 0.5 g and bezafibrate f0.2 g at 8-h intervals. The mean steady-state concentration of CPIB in serum was 34 times higher than that of bezafibrate, which was due to the considerable cumulation of CPIB, whereas no cumulation of bezafibrate was observed. This is supported by comparison of the AUCs, and of the maximum and mean concentrations of bezafibrate after the first and last doses. beta (0.44 and 0.49 h(-1)) and the half-lives (1.6 and 1.4h) were almost identical after the first and last doses of bezafibrate. The median total clearances of CPIB and bezafibrate amounted to 10.5 and 142.5ml/min, respectively, if complete absorption of both drugs is assumed. Since the apparent volumes of distribution were in the same range for both drugs, the amount of drug present in the organism in steady-state also differed by a factor of approximately 30 under the usual dosage regimen.