Cross-linked high amylose starch derivatives as matrices for controlled release of high drug loadings

Selection of hydrogels as excipients in controlled drug release systems dep ends on the characteristics of the gel and of the drug. Three types of deri vatives were synthesized from cross-linked high amylose starch (HASCL-6) by substitution of hydroxylic groups with cationic (carboxymethyl: CM), anion ic (aminoethyl: AE) and acetate (Ac) groups. These new polymeric excipients are able to control the release over 20 h from monolithic tablets loaded w ith 20 to 60% drug. Three drugs were used as model tracer: acetaminophen (u ncharged), acetylsalicylic acid (having an acidic group) and metformin (hav ing a basic group). It was found that the release of ionic drugs from CM-HA SCL-6 and AE-HASCL-6 matrices can be partially controlled by ionic interact ion between pendant groups of polymer and drugs. The substitution degree of HASCL-6 derivatives can also be varied to modulate the drug's release time . These derivatives represent a novel generation of pharmaceutical excipien ts, recommended for high loading dosage formulations. (C) 2001 Elsevier Sci ence B.V. All rights. reserved.