AN IN VITRO INVESTIGATION OF SUITABILITY OF PRESS-COATED TABLETS WITH HYDROXYPROPYLMETHYLCELLULOSE ACETATE SUCCINATE (HPMCAS) AND SODIUM ALGINATE IN OUTER SHELL FOR COLON TARGETING

The aim of present study was to develop a new colon targeting formulation, which can minimize the escape of Mesalazine completely in upper gastro-intestinal tract and ensure availability of maximum amount of drug to achieve the desired site i.e. distal colon. The use of press coated tablets with Hydroxypropylmethylcellulose acetate succinate (HPMCAS) and sodium alginate in outer shell was investigated. Two coats (upper and lower) were compressed onto the core tablets of Mesalazine using varying quantities of coating composition i.e. 100mg and 150mg each for lower and upper coat. The Mesalazine tablets coated by compressing 100 mg of HPMCAS each as upper and lower coat did not maintain integrity of the coats and released almost 100% of drug within 3 hrs. The tablets coated by compressing 150 mg of HPMCAS on the core tablets maintained good integrity during the dissolution test and prevented escape of Mesalazine totally in acid stage and buffer sage 1. However, the release of Mesalazine in subsequent buffer stage 2 was also affected. Mesalazine tablets coated with 1:1 blends of HPMCAS and sodium alginate could maintain good mechanical strength in acid stage and buffer stage 1 and released 81.65 % of drug within 5 hrs. While the tablets with higher proportion of Sodium alginate in coat although possessed good mechanical strength indicated slower release of drug. The amount of Mesalazine released from the tablets coated with higher proportion of HPMCAS alone was comparable to that released from the tablets coated with equal proportions of two pH sensitive polymers. These release indicating the usefulness of press coated tablets.