Adjusting drug diffusivity using miscible polymer blends.

Tuning the release rates of drugs was accomplished with miscible polymer blends. Dexamethasone (DX) was formulated in a miscible polymer blend composed of two poly(ether urethane)s, one in which DX diffuses relatively quickly and the other in which DX diffuses relatively slowly. Matrices that provide drug diffusion coefficients from 7 x 10(-13) to 3 x 10(-19) cm2/s were obtained by adjusting the blend ratio. Tunable diffusion coefficients were also achieved with partially miscible blends, such as poly(vinyl acetate) (PVAC)/cellulose acetate butyrate (CAB). However, similar tunable diffusion was not observed with an immiscible polymer blend composed of poly(carbonate urethane) (PCU) and polysulfone (PSF).