OBJECTIVE This study had a single-dose, randomized, open-label, 2-period, and 2-sequence crossover design to evaluate pharmacokinetic (PK) bioequivalence between the test and reference formulations. METHODS Of the 34 healthy male volunteers enrolled, 4 were excluded owing to consent withdrawal before drug administration and the remaining 30 subjects were administered 20 mg each of the test and reference formulations of omeprazole. The blood samples for PK analysis were collected at the scheduled time-points, prior to dosing to 10 hours after dosing. Plasma concentrations of omeprazole were quantified by a liquid chromatography-tandem mass spectrometry method. Bioequivalence was assessed according to current guidelines issued by regulatory authorities. RESULTS The plasma concentration-time profiles of omeprazole were similar between the reference and test drugs. The geometric mean ratios (90% confidence interval: CI) of test to reference were 0.9104 (0.8538 - 0.9708) for peak plasma concentration (Cmax) and 0.9304 (0.8836 - 0.9796) for area under the plasma concentration-time curve from time zero to time of last measureable concentration (AUC0-t). CONCLUSIONS The results from the PK analysis suggested that the reference and test formulations of 20 mg omeprazole capsules were bioequivalent in healthy male subjects.