Tablets containing mesalazine as a model drug were coated using various combinations of two methacrylic acid copolymers, (Eudragit L100 and Eudragit S100) by spraying from aqueous systems. The Eudragit L100-Eudragit S100 (w/w) combinations studied were 1:0, 4:1, 3:2, 1:1, 2:3, 1:4, 1:5, and 0:1. The coated tablets were tested in vitro for their suitability for pH-dependent colon-targeted oral drug delivery. The dissolution profiles of the drug obtained from the studied tablets demonstrate that the release of the drug could be manipulated by changing the Eudragit L100-Eudragit S100 ratios in the combinations within the pH range between 6.0 and 7.0 in which the individual polymers are soluble, and a coating formulation consisting of a combination of the two polymers can overcome the issue of high gastrointestinal (GI) pH variability among individuals. The results also demonstrate the feasibility of using aqueous dispersions of Eudragit L100-Eudragit S100 combinations for coating tablets for colon-targeted delivery of drugs, and that the formulation can be adjusted to deliver drug(s) at any other desirable site of the intestinal region of the GI tract in which pH of the fluid is within the range 6.0 to 7.0. For colon-targeted delivery of drugs, the proposed combination system is superior to tablets coated with either Eudragit L100 or Eudragit S100 alone.

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