In-vivo evaluation in rats of colon-specific microspheres containing 5-fluorouracil

The aims of this investigation were to determine the distribution in the gastrointestinal (GI) tract of Eudragit S-100 encapsulated colon-specific sodium alginate microspheres containing 5-fluorouracil (5-FU) in rats, and to perform pharmacokinetic and pharmacodynamic studies. Comparisons were with a control immediate-release (IR) formulation of 5-FU. 5-FU was distributed predominantly in the upper GI tract from the IR formulation but was distributed primarily to the lower part of the GI tract from the microsphere formulation. No drug was released in the stomach and intestinal regions from the colon-specific microspheres. Significantly, a high concentration of the active drug was achieved in colonic tissues from the colon-specific microspheres (P < 0.001), which was higher than the IC50 required to halt the growth of and/or kill colon cancer cells. Colon cancer was induced in rats by subcutaneous injection of 1,2-dimethylhydrazine (40 mg kg (-1)) for 10 weeks. The tumours induced were non-invasive adenocarcinomas and were in Duke's stage A. The 5-FU formulations were administered for 4 weeks after tumour induction. Non-significant reductions in tumour volume and multiplicity were observed in animals given the colon-specific microspheres. Enhanced levels of liver enzymes (SGOT, SGPT and alkaline phosphatase) were found in animals given the IR formulation of 5-FU, and values differed significantly (P < 0.001) from those in animals treated with the colon-specific microspheres. Elevated levels of serum albumin and creatinine, and leucocytopenia and thrombocytopenia were observed in the animals given the IR formulation. In summary, Eudragit S-100 coated alginate microspheres delivered 5-FU to colonic tissues, with reduced systemic side-effects. A long-term dosing study is required to ascertain the therapeutic benefits.