Pharmacokinetic properties and bioequivalence of olmesartan medoxomil/hydrochlorothiazide in healthy Korean male subjects

Olmesartan medoxomil inhibits the vasoconstrictor effects of angiotensin II. Hydrochlorothiazide (HCTZ) promotes sodium excretion, resulting in a reduction of plasma volume and peripheral resistance. A combination of these agents is known to have a greater effect for the treatment of hypertension than monotherapy with either one of these components. Objective: To assess bioequivalence between fixed-dose combination of olmesartan medoxomil and hydrochlorothiazide (HCTZ) in healthy Korean subjects. Methods: 40 healthy Korean volunteers were randomized into two groups. After administration of a single dose of investigational products, blood samples were collected before study drug administration (baseline) and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, and 36 hours after study drug administration. The plasma concentrations of olmesartan and HCTZ were measured by LC-MS/MS. The pharmacokinetic parameters were calculated, and the 90% confidence intervals (CIs) of the geometric mean ratio (test/reference) of the parameters were obtained by analysis of variance (ANOVA) on logarithmically transformed data. Results: The corresponding 90% CIs for the geometric mean ratio of the test to reference drugs were 0.93 - 1.04, 0.93 - 1.04, and 0.95 - 1.10. For HCTZ treatments, the 90% CIs for the geometric mean ratio of test to reference drugs were 0.95 - 1.03 for AUC_last, 0.96 - 1.03 for AUC∞, and 0.89 - 1.04 for C_max. Conclusion: This study demonstrated that the test and reference products met the regulatory criteria assuming bioequivalence. Both formulations were safe and well tolerated, and there were no noteworthy differences in the safety profiles of the test and reference drugs.