Permeability and swelling studies on free films containing inulin in combination with different polymethacrylates aimed for colonic drug delivery

The aim of this study was to assess some permeability and swelling characteristics of free films prepared by combination of inulin as a bacterially degradable system and time- or pH-dependent polymers as a coating formulation for colonic drug delivery. Different free films were prepared by casting and solvent evaporation method. Formulations containing inulin with Eudragit RS, Eudragit RL, Eudragit RS–Eudragit RL, Eudragit FS and Eudragit RS–Eudragit S with different ratios of inulin were prepared. After preparation, free films were evaluated by water vapor transmission test, swelling experiment and permeability to indomethacin and theophylline in different media. Formulations containing Eudragit FS had high resistance to water vapor permeation; but were unable to protect premature swelling and drug release in simulated small intestine media. Also, combination of Eudragit RS and Eudragit S had no suitable characteristics for colon delivery. However, Eudragit RS and Eudragit RL in combination with inulin made free films which had more swelling and permeation of drug in the colonic medium rather than the other media. It was shown that formulations containing sustained release polymethacrylates in combination with inulin have more potential as a coating system for specific colon delivery compared with pH-dependent polymers.