Enteric polymers as binders and coating materials in multiple-unit site-specific drug delivery systems

The aim of this study was to develop a multiple-unit, site-specific drug fo rmulation allowing targeting of drug release in the colon. Initially, chara cteristics of matrix pellets containing various enteric polymers as binders were tested. An enteric coating was then added to the formulations. Ibupro fen and furosemide were used as model drugs. The former is absorbed through out the gastrointestinal tract, the latter only from upper parts. Methacryl ate copolymers, hydroxypropyl methylcellulose acetate succinates and cellul ose acetate phthalate were used as enteric polymers. The properties of the products were initially tested via dissolution studies at different pHs, th en via bioavailability studies in healthy volunteers. The main conclusion w as that drug release can be targeted on the distal past of the small intest ine and the colon by preparing film-coated matrix pellets in which enteric polymers dissolving at pH approximate to 7 have been used both as binders i n the pellets and as coating material. This conclusion is based on the find ing that absorption of ibuprofen from the formulations developed was adequa te, with a lag-time of about 2 h and t(max) values at 4-5 h, where as absor ption of furosemide from the analogous products was negligible. It was also found that uncoated pellets as such could represent a slow-release formula tion for furosemide, a problem drug as far as modified-release products are concerned. (C) 1999 Published by Elsevier Science S.A. All rights reserved .