Pharmacokinetics and bioequivalance of five commercially available formulations of omeprazole: a preliminary report

Reasons for performing study:

The pharmacokinetics and bioequivalence of different formulations of omeprazole have not been published.

Objectives:

To compare the pharmacokinetics and bioavailability of 4 commercially available formulations of omeprazole to an existing reference formulation. Study design: A single dose cross-over bioequivalence study.

Methods:

Six 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.

Results:

The mean (± s.d.) area-under-thecurve (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.

Conclusions:

The 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