PREPARATION, CHARACTERIZATION AND APPLICATION OF LINEAR DEXTRINS .6. GENERAL APPLICABILITY AND MECHANISM OF PROGRAMMED RELEASE FROM AMYLODEXTRIN TABLETS

This study reports the successful application of amylodextrin as a uni que excipient in the design of programmed release systems. Physical mi xtures of amylodextrin with the model compounds theophylline, paraceta mol, methyl-PABA, prednisolone, atrazine, procaine HCl and potassium d ichromate, respectively, were compressed into almost non-porous tablet s and tested on their release profile, determined at pH 6.8 in the USP XXI paddle apparatus. All tablets did not disintegrate and showed alm ost constant release rates. Zero-order release of paracetamol was not affected by pH and ionic strength of the dissolution medium. Lubricati on with magnesium stearate was found not to impair the release profile of potassium dichromate-amylodextrin tablets. Zero-order release from the amylodextrin tablets is explained by the mechanism of water penet ration into the polymer associated with polymeric relaxations controll ing the drug diffusional release. Immersion in phosphate buffer of tab lets, compressed from a physical mixture of amylodextrin with neutral red, indeed demonstrated movement with an almost constant rate of a co loured front into the delivery system.