Modelling of sustained release of water-soluble drugs from porous, hydrophobic polymers.

The release behaviour of water-soluble drugs from hydrophobic, porous polymeric matrices is complicated by the dissolution of the drug in the water-filled pores under quiescent conditions. Mathematical models are presented for drug release above and below the solubility limit of the drug in the dissolution medium, for constant void fraction (porosity). Experimental studies of KCl release from the porous ethyl cellulose tablets in water at 37 degrees C are explained in terms of dissolution-controlled and diffusion-controlled steps of the release mechanism.