Graft copolymers of ethyl methacrylate on waxy maize starch derivatives as novel excipients for matrix tablets: Drug release and fronts movement kinetics

The graphs show the drug release and fronts movement profiles for matrices prepared with freeze-dried (FD) graft copolymers of ethyl methacrylate (EMA) and waxy maize starch (MS) or hydroxypropylstarch (MHS), using as model drugs anhydrous theophylline (T) or diltiazem HCl (D). The drug release markedly depends on the drug solubility and the carbohydrate nature, decreasing with the reduction in the surface exposed to the dissolution medium (radial release studies). The fronts movement kinetic reveals a faster water uptake for the most hydrophilic copolymer (MHS derivative) and a nearly constant erosion movement typical of inert matrices.