Bioequivalence Study of Donepezil Hydrochloride Tablets in Healthy Male Volunteers

The objective of this study was to investigate the bioequivalence of two formulations of 5 mg donepezil HCL tablets: Tonizep as the test and Aricept as the reference. The two products were administered as a single oral dose according to a randomized two-phase crossover with a 3-week washout period in 20 healthy Thai Male volunteers. After drug administration, serial blood samples were collected over a period of 216 hours. Plasma donepezil concentrations were measured by high performance liquid chromatography with UV detection. Pharmacokinetic parameters were analyzed based on noncompartmental analysis. The logarithmically transformed data of AUC(0-∞) and C(max) were analyzed for 90% confidence intervals (CI) using ANOVA. The mean (90% CI) values for the ratio of AUC(0-∞) and C(max) values of the test product over those of the reference product were 1.08 (1.02-1.14) and 1.08 (0.99-1.17), respectively (within the bioequivalence range of 0.8-1.25). The median T(max) for the test product was similar to that of the reference product (2.0 hr), and the 90% CI for the T(max) difference between the two preparations was -0.19 to 0.29 hr and within the bioequivalence range of ± 20% of the T(max) of the reference formulation. Our study demonstrated the bioequivalence of the two preparations.