RESUMO
To perform in vitro release-dissolution studies of sustained release theophylline forms commercialized in Chile, 5 sustained release products were studied according to the specifications of the 7th supplement of the United States Pharmacopoeia Convention. Release and dissolution rates were compared with a rapid release aminophylline form. The identity, validation and active principle content of each product was also studied. All the studied forms complied with the quality requirements of the USP XII. The dissolution rate constants of the products at pH 6 ranged from 0.0583 to 0.2130, compared with 7.1 for the rapid release form. The dissolution of all products, except one, was pH dependent. These results underscore the need to systematically study the quality of pharmaceutical products considered similar, whose differences could have potential risks for patients