Studies of chitosan/Kollicoat SR 30D film-coated tablets for colonic drug delivery.

The aim of the study was to define in vitro and in vivo characteristics of chitosan/Kollicoat SR30D film-coated tablets of theophylline for colonic delivery. The tablet cores were coated to different film thicknesses with blends of Kollicoat SR30D and chitosan (2.5:1, 3.5:1, and 5:1, w/w). Swelling and drug release studies were carried out in simulated gastric fluid, simulated intestinal fluid and simulated colonic fluid, respectively. The mechanism of drug release was determined using the Korsmeyer-Peppas model. The in vivo degradation of the tablets was also studied in rats. The swelling behavior and drug release depended on the composition of the coating, as well as the ratio of Kollicoat SR30D to chitosan. The coating was susceptible to enzymatic action, and more accessible to bacterial enzymes than beta-glucosidase enzyme. The extent of swelling and digestion correlated with the amount of chitosan within the coating. The drug release data fit well into the Korsmeyer-Peppas equation, indicating that the drug release was controlled by polymer relaxation. The in vivo pharmacokinetic studies of the coated tablets showed delayed T(max), decreased C(max) and prolonged MRT. Chitosan/Kollicoat SR30D coated tablets could deliver the drug to the targeted site for local action.