Drug release from starch-acetate films

The aim of the present work was to compare the drug release rates from the native and acetylated starches. The average degree of acetyl substitution per glucose residue of potato starch was either 1.9 (SA DS 1.9) or 2.6 (SA DS 2.6). Bovine serum albumin (BSA) (mol. wt. 68,000), FITC-dextran (mol. wt. 4400), timolol (mol. wt. 332, log P=1.91) and sotalol–HCl (mol. wt. 308, log P=−0.62) were used as model drugs. All of the model drugs were released rapidly from the potato starch film in PBS pH 7.4 with and without α-amylase in the dissolution medium (t_50% varied from 0.17 to 3.37 h). When compared to the potato starch film, all of the studied drugs were released at a substantially slower rate from the SA films in the corresponding mediums. The release of the smaller drugs (sotalol, timolol) from the SA films was faster than that of the macromolecules (FITC-dextran, BSA). Furthermore, sotalol was released faster than the more lipohilic timolol from the SA films. Release of macromolecules from the SA films was biphasic with and without α-amylase in the dissolution medium: an initial fast release phase was followed by a slower release phase (SA DS 1.9) or no release occurred after the initial phase (SA DS 2.6). All of the drugs were released faster from the SA DS 1.9 film than the weight loss of the film itself. When compared to the SA DS 1.9 film, the model drugs (except sotalol) were released slower from the SA DS 2.6 film. The macromolecule release from the SA DS 2.6 film was erosion-controlled. The weight loss of the SA DS 2.6 film was slow with and without α-amylase in the incubation medium. The present results show that acetylation of potato starch can substantially retard drug release. The drug release profiles may be controlled by the degree of substitution, since drug release from the SA DS 1.9 film was faster than the corresponding release from the SA DS 2.6 film.