Pharmacokinetics and Bioequivalance of Five Commercially Available Formulations of Omeprazole: A Preliminary Report

Abstract

Reasons for performing studyThe pharmacokinetics and bioequivalence of different formulations of omeprazole have not been published.ObjectivesTo compare the pharmacokinetics and bioavailability of 4 commercially available formulations of omeprazole to an existing reference formulation.Study designA single dose cross‐over bioequivalence study.MethodsSix adult Thoroughbred horses were used. Two generic buffered formulations (OG and AG), one commercial enteric coated formulation (GZ) and one compounded enteric coated formulation (BO) were compared to the reference buffered formulation (GG). Each formulation was administered at a total dose of 2 g (equivalent to 4 mg/kg bwt for a 500 kg horse) in a cross‐over design. Blood samples were collected at 0, 15, 30, 45, 60, 75, 90, 105, 120, 150, 180, 210, 240, 300 and 360 min, the plasma was separated and frozen. Plasma omeprazole concentrations were determined by UPLC‐MS. Noncompartmental pharmacokinetic analyses were performed using PK Solver.ResultsThe mean (± s.d.) area‐under‐the‐curve (AUC0‐t/0‐inf_obs) (μg/ml*min), Cmax (μg) and Tmax (min) for each formulation was; OG – 59.4 ± 20.1, 0.37 ± 0.12, 87.5 ± 38.4; AG – 77.3 ± 53.7, 0.34 ± 0.24, 170.0 ± 62.0; GZ – 102.9 ± 51.1, 0.86 ± 0.68, 67.5 ± 29.6; BO – 88.0 ± 37.4, 0.59 ± 0.39, 95.0 ± 47.1; GG – 57.5 ± 35.3, 0.41 ± 0.22, 57.5 ± 19.9.ConclusionsThe results of this study suggest that differences are present between commercially available formulations of omeprazole. Caution should be exercised in extrapolating results of clinical studies from one formulation to another.Ethical animal research: This study was performed under an ethics permit issued by the NSW Department of Primary Industries and in accordance with relevant state laws and legislation. Explicit owner informed consent for participation in this study was not stated. Sources of funding: This study was funded by a grant from the Grayson‐Jockey Club Research Foundation. Competing interests: The manufacturers of Gastrozol (GZ), Abgard (AG) and BOVA (BO) have previously funded research by B.W. Sykes. None of the companies contributed to the present study.