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A quite large number of drugs are characterized by a relatively slow dissolution kinetic and limited solubility in water. As a consequence different approaches have been proposed to improve their bioavailability. Supercritical fluid technology can be used in order to enhance the properties of the drugs. Among the different possible techniques, RESS and SAS can be considered. Due to the low solubility of many drugs in supercritical carbon dioxide, antisolvent techniques can be often employed. In this paper the results obtained with the precipitation of an anti inflammatory drug, nimesulide, from different organic solvents are presented. The characteristics of the precipitated drug are strongly influenced by the solvent. The interactions between solvent and drug are studied in order to understand their influences. The antisolvent precipitated drugs are compared with the drugs obtained from the same solvents but evaporating the solvents under vacuum. Dissolution rates determinations and physical characterizations of the particles obtained were also performed in order to better understand the influence of the solvent nature.

The impregnation of an anti-inflammatory drug, nimesulide, on chemically cross-linked PVP and on physically-linked PVP has been performed using supercritical carbon dioxide as solvent and operating at 313.15 and 333.15 K and pressures ranging from 130 to 220 bar. The experimental impregnation curves representing the impregnated quantity of drug versus time have been modelled using differential mass balances for the fluid and the solid phases. A simple model based on the assumptions of negligible axial dispersion and plug flow regime in the column was used to correlate the experimental data.