Comparative Potency and Dissolution Performance of Internationally Available Piroxicam Products

Summary

Generic drug products are marketed throughout the world and are generally regarded as being equivalent to the name brand product. Piroxicam is a widely prescribed nonsteroidal antiinflammatory drug and is marketed under the Pfizer tradename Feldene® or Felden®. In countries with no patent laws or where the Feldene® patent has expired, the drug is available under various trademarks by many different producers. Differences in formulations produced by different manufacturers can be assessed by measuring dissolution rate and potency. In this study, the United States Pharmacopeia (USP) dissolution and potency tests were applied to 85 generic piroxicam products obtained from 21 countries in an attempt to evaluate if the available formulations met standard quality assurance tests. The results show that of the 85 piroxicam products tested, 17 products met the USP dissolution standards and 68 products failed. Of the 85 products tested for potency as a percentage of label claim, 50 products failed the USP criteria. Overall, 91% of the generic piroxicam products evaluated failed to meet the routine in vitro USP quality assurance criteria for potency and/or dissolution. The substantial differences observed in this study regarding performance of piroxicam dosage forms available worldwide have possible implications in terms of product equivalency and standards at an international level. While these results cannot be used to draw clinical conclusions without bioavailability data, they should nonetheless be kept in mind by healthcare practitioners. These data should be evaluated along with other relevant considerations before physicians and pharmacists make decisions regarding the interchange of these products.