Evaluation of dextran-flufenamic acid ester as a polymeric colon-specific prodrug of flufenamic acid, an anti-inflammatory drug, for chronotherapy

Dextran-flufenamic acid ester (Dex-FFA) with varied degree of substitution (DS) was prepared by imidazolide method. Dex-FFA was stable in pH 1.2 or pH 6.8 buffer. The depolymerization degree of Dex-FFA by dextranase decreased as DS increased. Dex-FFA with DS of 13 or 20 released FFA up to 70% or 21% of the dose, respectively, on 24 h-incubation with the 10% cecal contents. FFA was liberated up to 29% of the dose on 24 h-incubation of dextranase pre-treated Dex-FFA with the homogenates of the upper intestine, whereas no FFA was detected devoid of dextranse-pretreatment. Upon oral administration of Dex-FFA (DS 13, 20 mg equivalent of FFA/kg) or FFA (10 mg/kg) to rats, tmax for FFA with Dex-FFA administration delayed approximately 6 h compared with that of free FFA administration, while Cmax for FFA was similar. The plasma level for FFA became greater around 6 h after administration of Dex-FFA than free FFA and it was maintained throughout the period of 24 h-experiment. Dex-FFA markedly attenuated gastric ulcerogenicity of FFA. Taken together, Dex-FFA could be useful as a colon-specific prodrug which possesses anti-inflammatory properties and offers opportunities as a chronotherapeutic approach for the treatment of arthritis.