Comparative dissolution performance of internationally available piroxicam products

Piroxicam is a widely used nonsteroidal antiinflammatory drug available worldwide under various trade names by several manufacturers. Only one brand of piroxicam (Feldene) is currently marketed in the U.S., and the United States Pharmacopeial Convention established an official dissolution requirement for piroxicam in 1985. The purpose of this study was to evaluate and compare the dissolution performance of several internationally available piroxicam products using the United States Pharmacopeia (USP) dissolution test for piroxicam capsules. Of 25 brands of piroxicam capsules evaluated, 72 percent of the brands failed to meet the USP requirement, several by a wide margin. Although there is no specific USP dissolution test for tablets, the test for capsules was applied to five different brands of piroxicam tablets, and 80 percent of the tablet brands tested failed to meet the USP requirement. Although comparative bioavailability studies would be required to establish any definitive relationship between dissolution test performance and bioavailability, the failure of most of these products to meet the USP requirement for dissolution indicates formulation differences that could result in altered bioavailability. The substantial differences in dissolution performance observed among the piroxicam oral dosage forms tested have implications concerning the equivalency and standards of multisource products available on the international market, and should be taken into account by health care providers worldwide.