Comparative Pharmacokinetics and Bioequivalence Studies of Three Oral Cephalexin Monohydrate Formulations

This paper aims at assessing the pharmacokinetics and bioequivalence of two locally manufactured cephalexin capsules in comparison with a reference product in Sudan. Bioequivalence of two locally produced cephalexin capsule formulations was investigated in 24 healthy volunteers following administration of a single dose (500 mg) of each product and a reference product in open randomized crossover studies within a one week washout period. Blood samples were drawn over a 6-hour interval and plasma concentrations of cephalexin were measured using HPLC-UV technique. Pharmacokinetic parameters and bioavailability measures were determined using non-compartmental analysis. Two one-sided t-test and ANOVA analysis showed no statistically significant differences in pharmacokinetic parameters between the two formulations and the reference product (P 0.05). The mean values of AUC∞, and Cmax, are 33.4, 35 and 32.5 µgh/ml; 19, 17.4 and 17.3 µg/ml for reference product A and test brands B and C, respectively. Tmax was about 1 hour for all three formulations. 90% Confidence Intervals (CI) of the ratios of means for the two formulations were 93.46 - 106.54 and 86.62 - 113.38% for AUC∞, 86.65 - 113.35 and 88.25 - 111.75% for Cmax, and 92 -107.9 and 89.9 . 110% for Tmax. Since the 90% CI values were within the interval proposed by the FDA (80 . 120%), the test products are deemed bioequivalent to the reference product. The three formulations are expected to give the same levels and the same therapeutic effect and therefore can be used interchangeably.