Bioavailability of omeprazole 20 mg capsules containing omeprazole 22.5% enteric coated pellets versus a reference product in healthy Bangladeshi male subjects: an open-label, single-dose, randomized-sequence, two-way crossover study.

OBJECTIVE: Omeprazole 20 mg enteric coated capsule formulation is generally prepared either with omeprazole 8.5% or omeprazole 7.5% enteric coated pellets to accommodate in capsule Shell 2, but the use of omeprazole 22.5% enteric coated pellets in capsule Shell 5 for the same amount of omeprazole is a new concept and for the first time in the Bangladesh market. This study was conducted to compare the relative bioavailability and pharmacokinetic properties of two omeprazole 20 mg capsule formulations namely Xeldrin®20 (ACI Ltd., Bangladesh) encapsulated with omeprazole 22.5% enteric coated pellets, as test product and Losec®20 (AstraZeneca, Wilmington, DE, USA) as reference product and to assess whether these formulations meet the FDA requirement for bioequivalence.

MATERIALS AND METHODS: 24 non-smoking healthy Bangladeshi male subjects participated in this open-label, randomized-sequence, single- dose, two-way crossover study. Subjects were randomly assigned to receive test formulation, followed by reference formulation or vice versa, as a single dose of 20 mg capsule after 12 h overnight fasting. A washout period of 1 week was maintained between the treatments. Blood samples were collected before study drug administration (baseline) and at 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 7.0, 9.0, and 12.0 h after study drug administration. Serum omeprazole concentrations were determined using a validated HPLC method with UV detection. The pharmacokinetic parameters were determined by the non-compartmental method. The two formulations were to be considered bioequivalent if the 90% confidence intervals (CI) for the ln-transformed ratios of pharmacokinetic parameters were within the predetermined equivalence range of 80 - 125% according to the guidelines of the US Food and Drug Administration (FDA). Tolerability was assessed on the basis of adverse effects, monitoring vital signs, ECG and laboratory tests at baseline and after completion of the study with the assistance of registered physicians.

RESULTS: All 24 subjects completed the study without any adverse effect reported. After administering a single dose of 20 mg of each omeprazole formulation, the obtained mean (SD) values for the test and reference products were 608.40 (116.37) and 588.56 (98.36) ng/ml for Cmax; 1.83 (0.25) and 2.00 (0.30) h for tmax; 1,635.77 (581.25) and 1,639.58 (652.54) h-ng/ml for AUC0-12; and 1,721.12 (572.07) and 1,805.58 (856.39) h-ng/ml for AUC(0-∞) respectively. The mean t(1/2) was 3.33 (1.61) and 3.57 (1.24) h for test and reference product respectively. From paired t-test, no significant differences were observed (p > 0.05) for any pharmacokinetic parameters. The point estimates (90% CI) for the test/reference ratios of the ln-transformed AUC(0-12), AUC(0-∞) and C(max) mean values were 100.73% (91.40 -111.01%), 98.29% (88.45 -109.24%) and 103.06% (99.05 - 07.24%) respectively, which fell within the predetermined FDA bioequivalence range of 80 - 125%.

CONCLUSION: This single-dose study found that the test (Xeldrin®20) and reference (Losec®20) 20 mg capsule formulations of omeprazole in these fasting healthy male Bangladeshi subjects met the FDA regulatory criteria for bioequivalence.