Organic acids as excipients in matrix granules for colon-specific drug delivery

Interest exists in developing site-specific systems for release of a drug i n the lower part of the small intestine or in the colon. The aim of this st udy was to investigate whether drug release rates from enteric matrix granu les could be influenced by using organic acids as excipients. Ibuprofen was used as a model drug and Eudragit(TM) S and Aqoat(TM) AS-HF as enteric pol ymers. The dissolution rates of the drug were investigated at different lev els of pH (5.8, 6.8 and 7.4). Drug absorption was studied in bioavailabilit y tests in healthy volunteers. In vitro/in vivo correlation was also invest igated. It was concluded that although inclusion of an organic acid in a fo rmulation retarded in vitro release of the model drug, no corresponding eff ect was evident in in vivo studies. Bioavailability tests are therefore imp ortant early on during development of new dosage forms or formulations. Alt hough no correlation between in vitro and in vivo results was generally evi dent correlation could be demonstrated for individual formulations followin g mathematical transformation of data. (C) 1999 Elsevier Science B.V. All r ights reserved.