Bioequivalence study of two capsule formulations of omeprazole in healthy volunteers

The study was conducted in order to assess the bioequivalence of two capsule formulations (test and reference) containing 20 mg of omeprazole (5-methoxy2-[[4-methoxy-3,5-dimethyl-2-pyridinyl) methyl]sulfinyl]-1H-benzimidazole, CAS 73590-58-6). Fifty healthy male and female volunteers were treated in a single-centre, randomised, repeated-dose (once daily for six consecutive days), open-label, two-way crossover study, with a washout period of at least 9 days between treatments. Plasma samples were collected up to 12 h post-dosing for the determination of omeprazole by HPLC with photodiode array detector (DAD). The evaluation of bioequivalence was based on the following pharmacokinetic parameters that were calculated by standard non-compartmental methods: area under the plasma concentration-time curve from zero to the time of the last quantifiable concentration (AUC(t)) and that extrapolated to infinity (AUC) and the maximum observed concentration (C-max). The 90% confidence interval around the ratios (test/reference) (obtained by analysis of variance, ANOVA) were 0.92-1.04 for C-max, 0.88-1.05 for AUC(t), and 0.88-1.05 for AUC, i.e., within the predefined acceptable range for the conclusion of bioequivalence. The study indicated that the test and reference formulations containing 20 mg of omeprazole are bioequivalent in terms of both the rate and extent of bioavailability.