Cross-linked amylose as matrix for drug controlled release. X-ray and FT-IR structural analysis

Far cross-linked amylose (CLA) tablets prepared by direct compression, a Li near increase in cross-linking degree (cld) defined as percentage of epichl orohydrin cross-linker/polymer, generates non-monotonous variation of drug release time. Controlled release (up to 20-24 h) properties were obtained o nly for tablets from CLA (Contramid(TM)) with relatively low cld (CLA-2 up to CLA-6). Moderate increase in cld (CLA-15) generates a sharp decrease in the release time (2-6 h). This is a particular characteristic of the CLA ma trix. The controlled release properties were related to the X-ray pattern o f the dry CLA network. The increase in dd induces a transition from B-type (double helix) to a predominat V-type (single helix) and to more amorphous conformation of CLA powders. Furthermore, FT-IR data indicated low free wat er content at low cld. For low cross-linked CLA, chains are closely located and stabilized by HO groups involved in hydrogen bonding and thus more res istant to hydration and more appropriate for the control of drug release. ( C) 1998 Elsevier Science Ltd. AU rights reserved.