Leaching of pectin from mixed pectin insoluble polymer films intended for colonic drug delivery

Investigations intended to combine pectin HM of calcium pectinates with commercially available aqueous polymer dispersions for colon-specific drug delivery have been conducted on isolated films. The mixed films were prepared from Aquacoat(R) ECD 30, Surelease(R) clear, Eudragit(R) RS30D or Eudragit(R) NE30D containing 5, 10 or 15% w/w (related to insoluble polymer content) of pectin HM or 10% w/w of calcium pectinates. The kinetics of pectin leaching from the mixed films, incubated in 0.05 M acetate-phosphate buffer (pH 4.5, 37 degrees C) in the absence of pectinolytic enzymes, showed that pectin HM or calcium pectinates were quickly released from the different films except from the mixed pectin/Eudragit(R) RS films. Moreover, in these cases, the leaching of pectin from Eudragit(R) RS films containing up to 10% w/w (related to Eudragit(R) RS polymer content) of pectin HM or pectin LM, was significantly faster in the presence of enzymes than in absence. These results indicate that the associations of pectin HM or LM and Eudragit RS are likely to give more suitable coating materials for colon-specific drug delivery than the other combinations. (C) 1998 Elsevier Science B.V. All rights reserved.