In vitro evaluation of calcium pectinate: a potential colon-specific drug delivery carrier

Calcium pectinate (CaP)--the insoluble salt of pectin--can potentially be used as a colon-specific drug delivery system. The use of CaP as a carrier was based on the assumption that, like pectin, it can be decomposed by specific pectinolytic enzymes in the colon but that it retains its integrity in the physiological environment of the small bowel. The biodegradation of the carrier was characterized by monitoring the percent cumulative release of the insoluble drug indomethacin, incorporated into pectin or CaP matrices. Compressed tablets of pectin and indomethacin were analyzed for degradation in the presence of Pectinex 3XL, a typical pectinolytic enzyme mixture, and in the presence of the human colonic bacterium Bacteroides ovatus. The degradation of CaP-indomethacin tablets was assessed in the presence of Pectinex 3XL and in rat cecal contents. The release of indomethacin was significantly increased (end-time percentage cumulative release vs control) in the presence of Pectinex 3XL (89 +/- 20 vs 16 +/- 2 for CaP tablets), Bacteroides ovatus (12 and 22 vs 5.2 for pectin tablets), and rat cecal contents (61 +/- 16 vs 4.9 +/- 1.1 for CaP tablets). The weight loss of tablet mass was significantly higher (end-time dry weight vs control) in the presence of Pectinex 3XL (0 vs 75 +/- 6% of initial weight for CaP tablets). These findings indicate the potential of CaP, compressed into tablets with insoluble drug, to serve as a specific drug delivery system to the colon.