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Biphasic drug release: permeability and swelling of pectin/ethylcellulose films, and in vitro and in vivo correlation of film-coated pellets in dogs.

The major objectives of this study were i) to evaluate the permeability and swelling characteristics of isolated films prepared by mixing of pectin with ethylcellulose; and ii) to assess the absorption and in vitro/in vivo correlation (IVIVC) of 5-FU film-coated colon-targeted pellets in dogs. Free films were prepared by casting and solvent evaporation method. These free films were evaluated by swelling experiment and permeability to 5-FU in different media. Pectin/ethylcellulose films had suitable characteristics for colonic delivery; and when the addition of pectin was up to the ratio of 30%, the swelling and permeability of the mixed films was significantly increased in the simulated colonic fluid (SCF). Pharmacokinetic study in dogs gave Tmax/Cmax of 14 h/1.6 microg/ml and 16 h/1.7 microg/ml for total weight gain (TWG)-22% and 18% coated pellets, respectively. The plasma 5-FU levels of the TWG-22% and 18% coated pellets were maintained at a much lower level with a mean residence time (MRT) of 18-20 h, longer than 2.1 h for 5-FU uncoated pellets, confirming delayed absorption. There was no statistically significant difference in the area under the plasma concentration vs. times curve (AUC) values between the uncoated pellets and the coated pellets. Moreover, a good linear regression relationship was observed between the percent in vitro dissolution in SCF and the percent absorption or percent AUC. It was concluded that i) pectin within the mixed films were susceptible to colonic enzymes, and the film-coated pellets are potentially useful for colonic drug delivery; and ii) in vitro dissolution testing in SCF could be used to establish certain IVIVC for the colon-specific drug delivery systems activated by microflora.