Dissolution of omeprazole from delayed-release solid oral dosage forms

The evaluation of the biopharmaceutical quality of omeprazole enteric-coated products (granules in capsules) with respect to its dissolution characteristics is not specifically regulated in any of the most common official pharmacopoeia. USP 23 includes a general monograph for enteric-coated products. This paper reports the evaluation of the medium pH effect on the dissolution rates of omeprazole from four omeprazole-containing products of different manufacturers. It is concluded that the USP 23 recommended dissolution procedure for enteric-coated products is not suitable due to the degradation of omeprazole under such conditions. Furthermore, the medium with pH 8.0 showed different dissolution rates not observed at pH 7.4, allowing discrimination between products of different manufacturers.