Supersaturated controlled release matrix using amorphous dispersions of glipizide

Abstract

Spray dried dispersions (SDDs) of glipizide, a BCS Class II model drug, were prepared using various grades of hydroxypropyl methylcellulose acetate succinate (HPMCAS) and copovidone S-630 as carriers. The SDDs appeared as a single amorphous phase with up to 60% drug loading level as revealed by X-ray powder diffraction (XRPD), modulated differential scanning calorimetry (mDSC) and scanning electron microscopy (SEM). Supersaturated micro-dissolution testing of various SDDs in fasted state simulated intestinal fluid showed prolonged supersaturation state (up to 180min) with solubility increases of 5.2-13.9 fold relative to crystalline drug under similar conditions. Solubility and stability characteristics of the most desirable SDDs in terms of relative dissolution AUCs (AUC(SDD)/AUC(crystalline)) and supersaturated concentration ratios (C180/Cmax) were determined. Results show that HPMCAS-based SDDs achieve a higher degree of supersaturation compared to Copovidone S-630 and that SDDs comprising HPMCAS-M and HPMCAS-H maintained stable supersaturated concentration. Dissolution data showed that SDD-loaded CR tablets provide stable supersaturated concentration within the hydrated matrix with increased rate and extent of drug dissolution over 24h. Co-existence of HPMCAS and HPMC within the hydrating matrix showed strong suppression of drug crystallization and allowed achievement of zero-order and slow-first order release kinetics.

Keywords: Amorphous solid dispersion; Controlled-release matrix tablet; Copovidone; Glipizide; Hydroxypropyl methylcellulose acetate succinate (HPMCAS); Spray drying.