In situ coating of 5-fluorouracil pellets by ethylcellulose and pectin powder mixture (8:3 weight ratio) in capsule at simulated gastrointestinal media provides colon-specific drug release in vitro. This study probes into pharmacodynamic and pharmacokinetic profiles of intra-capsular pellets coated in vivo in rats with reference to their site-specific drug release outcomes. The pellets were prepared by extrusion-spheronization technique. In vitro drug content, drug release, in vivo pharmacokinetics, local colonic drug content, tumor, aberrant crypt foci, systemic hematology and clinical chemistry profiles of coated and uncoated pellets were examined against unprocessed drug. In vivo pellet coating led to reduced drug bioavailability and enhanced drug accumulation at colon (179.13 μg 5-FU/g rat colon content vs 4.66 μg/g of conventional in vitro film-coated pellets at 15 mg/kg dose). The in vivo coated pellets reduced tumor number and size, through reforming tubular epithelium with basement membrane and restricting expression of cancer from adenoma to adenocarcinoma. Unlike uncoated pellets and unprocessed drug, the coated pellets eliminated aberrant crypt foci which represented a putative preneoplastic lesion in colon cancer. They did not inflict additional systemic toxicity. In vivo pellet coating to orally target 5-fluorouracil delivery at cancerous colon is a feasible therapeutic treatment approach.
Conventional fluid-bed and immersion film coating of hydrophilic zinc pectinate pellets by hydrophobic ethylcellulose is met with fast drug release. This study explored in situ intracapsular pellet coating for colon-specific delivery of 5-fluorouracil (5-FU). The solid coating powder constituted ethylcellulose and pectin in weight ratios of 11:0 to 2:9. Its weight ratio to pellets varied between 2:3 and 3:2. Pectin was used as excipient of core pellets and coating powder in view of its potential use in colon cancer treatment. Delayed 5-FU release and core pectin dissolution were attainable when the weight ratio of solid coating powder to pellets was kept at 3:2, and weight ratio of ethylcellulose and pectin in coating powder was kept at 8:3 with particle size of ethylcellulose reduced to 22 μm. In situ intracapsular wetting of pectin coat by dissolution medium resulted in the formation of ethylcellulose plug interconnecting with pellets through the binding action of pectin. Less than 25% of drug was released at the upper gastrointestinal tract. The majority of drug was released upon prolonged dissolution and in response to colonic enzyme pectinase, which digested core pellets.