An in vitro investigation into the potential for bimodal drug release from pectin/chitosan/HPMC-coated tablets

The influence of disintegrant on the water uptake and subsequent disintegration force developed was investigated in a simple tablet formulation. The results indicated that a reasonable correlation existed between water uptake and disintegration force for the disintegrants screened with cross linked polyvinyl pyrrolidone (PVP XL) showing a proportionally higher disintegration force for the amount of water imbibed. Two tablet formulations, intended to promote accelerated drug release in the colon, were prepared, with and without PVP XL, and film coated with a mixture of pectin, chitosan and HPMC. The two systems showed different drug release rates which were influenced by the pH of the dissolution medium. In the presence of pectinolytic enzyme, drug release was faster when compared to release in buffer alone for both systems although the mechanism differed for each. Drug release in simulated gastrointestinal conditions showed a bimodal profile with the increased drug release rate being triggered by the action of pectinolytic enzymes.