A NEW-GENERATION OF STARCH PRODUCTS AS EXCIPIENT IN PHARMACEUTICAL TABLETS .2. HIGH-SURFACE-AREA RETROGRADED PREGELATINIZED POTATO STARCH PRODUCTS IN SUSTAINED-RELEASE TABLETS

A new linear short-chain starch product was prepared by gelatinization of potato starch followed by enzymatic degradation, precipitation (re trogradation) and filtration. A high specific surface area was subsequ ently created by washing with ethanol or acetone or freeze-drying. Tab lets compressed from a mixture containing the starch product and 30% t heophylline at a force of at least 15 kN showed no disintegration and an almost constant (zero-order) sustained drug release. The delivery f rom these non-porous tablets proved to be a swelling-controlled solven t-activated mechanism, as was confirmed by the slow penetration of a s olvent front into the tablet. Drug release proved to be not affected b y the incorporation of magnesium stearate into the tablet or the prese nce of alpha-amylase in the dissolution medium, both features in contr ast to similar tablets compressed from conventional pregelatinized sta rches, which were prepared by gelatinization followed directly by ther mic dehydration. A specific surface area of 1.5 m(2)/g proved to be a prerequisite for the starch product to control drug release. A high su rface area (linear long-chain) amylose product showed a sustained but less linear release profile. Branched short and long-chain products wi th a high surface area produced disintegrating tablets and are therefo re not able to control drug release.