A bioequivalence study of six brands of cephalexin

The bioequivalence of six brands of cephalexin capsules or tablets was studied in six healthy volunteers in a crossover design. Single oral doses (1 X 500 mg) of each product were administered at intervals of 1 week. Bioequivalence was assessed by a urinary excretion method in which the drug was assayed by a sensitive and precise high pressure liquid chromatographic (HPLC) method. Statistical analysis of the cumulative urinary amounts of cephalexin excreted after 7 h indicated no significant differences between brand A and the other brands. However, brand C was significantly different from brands F and B. The various brands did not differ from each other with respect to urinary excretion rate, time to reach the urinary peak height, elimination rate constant and absorption rate constant. The study demonstrated that the six products of cephalexin were bioequivalent.