PECTIN CHITOSAN MIXTURES AS COATINGS FOR COLON-SPECIFIC DRUG-DELIVERY- AN IN-VITRO EVALUATION/

The ability of a multiple-unit dosage form to reach the colon intact h as been investigated, in vitro, using conditions chosen to simulate th e pH and times likely to be encountered during transit to the colon. S mall tablets were coated with either pectin USP or pectin in a 1:10 mi xture with chitosan. Indomethacin and paracetamol were used as model d rugs to represent poorly soluble and soluble compounds. Pectin alone w as able to protect the cores from premature release, but only when a s ubstantially thick coat was present. Pectin/chitosan mixtures achieved better protection at a lower coat weight. The use of pectinolytic enz ymes to simulate breakdown in the colon showed that the pectin/chitosa n mixture was susceptible to enzymic breakdown and allowed drug releas e to occur. The importance of pre-exposure of the tablets to condition s in the upper gastro-intestinal tract prior to exposure to the enzyme was noted. (C) 1998 Elsevier Science B.V. All rights reserved.