A pH-dependent colon targeted oral drug delivery system using methacrylic acid copolymers - I. Manipulation of drug release using Eudragit (R) L100-55 and Eudragit (R) S100 combinations

Lactose-based placebo tablets were coated using various combinations of two methacrylic acid copolymers, Eudragit (R) L100-55 and Eudragit (R) S100, b y spraying from aqueous systems. The Eudragit (R) L100-55-Eudragit (R) S100 combinations (w/w) 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 depen dent colon targeted oral drug delivery. The same coating formulations were then applied on tablets containing mesalazine as a model drug and evaluated for in vitro dissolution rates under various conditions. The disintegratio n data obtained from the placebo tablets demonstrate that disintegration ra te of the studied tablets is dependent on: (i) the polymers combination use d to coat the tablets, (ii) pH of the disintegration media, and (iii) the c oating level of the tablets. Dissolution studies performed on the mesalazin e tablets further confirmed that the release profiles of the drug could be manipulated by changing the Eudragit (R) L100-55 and Eudragit (R) S100 rati os within the pH range of 5.5 to 7.0 in which the individual polymers are s oluble respectively, and a coating formulation consisting of a combination of the two copolymers can overcome the issue of high gastrointestinal (GI) pH variability among individuals. The results also demonstrated that a comb ination of Eudragit (R) L100-55 and Eudragit (R) S100 can be successfully u sed from aqueous system to coat tablets for colon targeted delivery of drug s and the formulation can be adjusted to deliver drug at any other desirabl e site of the intestinal region of the GI tract on the basis of pH variabil ity. For colon targeted delivery of drugs the proposed combination system i s superior to tablets coated with either Eudragit (R) L100-55 or Eudragit ( R) S100 alone. (C) 1999 Elsevier Science B.V. All rights reserved.