pH-sensitive polymeric physical-mixture for possible site-specific delivery of ibuprofen.

Delivery of drugs to the large bowel has been extensively investigated during the last decade. The aim of this work was to study polymethacrylic acid-co-methylmethacrylate substituted with fatty acids (lauric, myristic, palmitic and stearic) at 20% substitution degree (PMA-LAUR20, PMA-MIR20, PMA-PALM20 and PMA-STEA20) or 40% substitution degree (PMA-LAUR40, PMA-MIR40, PMA-PALM40 and PMA-STEA40) for preparing a pH-sensitive physical mixture for site-specific delivery of ibuprofen chosen as a model drug. The preparation and characterization of the substituted polymers were described. In vitro release studies were conducted at different pH levels (3 h at pH 2.0, 2 h at pH 5.5, 4 h at pH 7.4 and until 24 h at pH 7.0) and phase-solubility diagrams of ibuprofen with the different substituted polymers were obtained at pH 7.0 to obtain information on the influence of amphiphilic polymers in increasing drug solubility and drug availability in the colon. Copyright 2003 Elsevier Science B.V.