Controlled release of drug via methylcellulose-carboxyvinylpolymer interpolymer complex solid dispersion.

The purpose of this research was to examine the controlled release of phenacetin (PHE) from solid dispersion by the formation of an interpolymer complex between methylcellulose (MC) and carboxyvinylpolymer (CP). The PHE/polymer composition ratio was fixed at 20:80 (w/w) in the solid dispersion. The effect of the MC/CP ratio and molecular weight of MC on the PHE release was studied. The release of PHE from the solid-dispersion granules depended on the MC/CP ratio, with a ratio of 50:50 giving the lowest rate of release. In aqueous solution, this MC/CP ratio resulted in the lowest transmittance, suggesting a maximal extent of interpolymer complex formation between MC and CP. Furthermore, at a MC/CP ratio of 50:50, the release of PHE from the solid dispersion granules decreased as the molecular weight of the MC increased, reaching a plateau at molecular weights >or=180,000. The contributions of diffusion and polymer relaxation to PHE release increased as the molecular weight of the MC increased. This study shows that it is feasible to control the release of PHE from MC-CP solid dispersion granules by modulating complex formation between MC and CP, which can be accomplished by altering the MC/CP ratio and the molecular weight of MC.