Comparative bioavailability of two formulations containing atenolol and chlortalidone associated in a 4:1 fixed combination

Atenolol quantification in human plasma by high-performance liquid chromatography: application to bioequivalence study

An accurate, precise, and sensitive high-performance liquid chromatography (HPLC) assay was developed for the determination of atenolol in human plasma samples to compare the bioavailability of 2 atenolol tablet (50 mg) formulations in 24 volunteers of both sexes. The study had an open, randomized, 2-period crossover design with a 1-week washout period. Plasma samples were obtained over a 24-hour interval. Atenolol concentrations were analyzed by combined reversed phase liquid chromatography and fluorescence detection (lambda(EX) = 258 nm, lambda(EM) = 300 nm). From the atenolol plasma concentration versus time curves, the following pharmacokinetic parameters were obtained: AUC(0-24h), AUC(0- infinity ), and C(max). The geometric mean of test/reference 50-mg tablets individual percent ratio was 102.2% for AUC(0-24h), and 101.6% for C(max). The 90% confidence intervals (CI) were 100.2% to 105.4% and 100.9% to 103.5%, respectively. Since the 90% CI for both C(max) and AUC(0-24h) were within the 80% to 125% interval proposed by the Food and Drug Administration, it was concluded that atenolol (50-mg tablets) test formulation was bioequivalent to the reference formulation, with regard to both the rate and extent of absorption.