Processing of carbamazepine PEG 4000 solid dispersions with supercritical carbon dioxide: preparation, characterisation, and in vitro dissolution

The purpose of this study was to apply the attractive technique of the supe rcritical fluid to the preparation of solvent-free solid dispersions. In pa rticular, the gas antisolvent crystallisation technique (GAS), using superc ritical carbon dioxide as processing medium, has been considered to prepare an enhanced release dosage form for of the poorly soluble carbamazepine, e mploying PEG 4000 as a hydrophilic carrier. The physical characterisation o f the systems using laser granulometer, powder X-ray diffraction, thermal a nalyses, and scanning electron microscopy was carried out: in order to unde rstand the influence of this technological process on the physical status o f the drug. The results of the physical characterisation attested a substan tial correspondence of the solid stale of the drug before and after treatme nt with GAS technique, whereas a pronounced change in size and morphology o f the drug crystals was noticed. The dramatic reduction of the dimensions a nd the better crystal shape, together with the presence of the hydrophilic polymer determined a remarkable enhancement of the in vitro drug dissolutio n rate. (C) 2001 Elsevier Science B.V. All rights reserved.