Bioequivalence of two rabeprazole formulations and pharmacokinetic variability by CYP2C19 genotype and sex in healthy Korean participants: A four-period replicated crossover study.

Rabeprazole is a highly variable drug for which demonstration of bioequivalence is often challenging, and CYP2C19 genotype and sex have been suggested as potential contributors to pharmacokinetic variability. We evaluated the pharmacokinetics, bioequivalence (BE), and tolerability of a generic rabeprazole formulation compared with the reference product in healthy Korean participants using an open-label, randomized, single-dose, two-sequence, four-period replicated crossover design with a scaled average BE (SABE) approach. Exploratory subgroup analyses according to CYP2C19 genotype and sex were also performed. Fifty-two participants received single 20 mg doses under fasting conditions, and 46 completed the trial. BE was evaluated using SABE and conventional average BE (ABE), with subgroup analyses by genotype and sex. Geometric mean ratios (GMRs) of the test to reference formulations were within the BE acceptance range under ABE and SABE approaches. The reference formulation showed high intra-CV in maximum plasma concentration (Cmax; 67.9%), consistent with the classification of rabeprazole as a highly variable drug. These results demonstrated bioequivalence between the test and reference formulations under both conventional average bioequivalence and scaled bioequivalence approaches.