(105c) Supercritical Precipitation of Acyclovir

The therapeutic activity of pharmaceutical entities is related to chemical structure and physical factors such as crystallinity and particle size. In the pharmaceutical area, fine particles with narrow particle size distribution are required to obtain a high surface area. In general, the high surface area will influence the bioavailability and the dissolution rate of pharmaceuticals. Acyclovir is a synthetic analogue of purynic nucleosides with antiviral activity. It is active above all against herpes simplex virus type 1 (HSV1) and type 2 (HSV2) and against varicella-zoster virus and its activity is highly selective for infected cells. In recent years, great interest has been expressed in the field of SCFs technology in an attempt to find alternative and improved methods of pharmaceutical processing. Among the different possible techniques, Rapid Expansion from a Supercritcal Solution (RESS), Supercritical AntiSolvent precipitation (SAS) and supercritical assisted atomization (SAA) can be considered. Due to the low solubility of many drugs and in particular of acyclovir in supercritical carbon dioxide only antisolvent based techniques (both SAS and SAA) can be employed. Aim of this work is to investigate two different antisolvent techniques (SAS and SAA) in order to obtain the precipitation of acyclovir, from organic and aqueous solutions using CO2 as antisolvent. Phase equilibria behaviour of the system acyclovir ?liquid solvent ? carbon dioxide was studied using a high pressure variable volume cell in order to evidence the influence of the drug on the phase boundaries of the binary system liquid solvent ? carbon dioxide. The influence of different apparatus on morphology and particle size will be investigated.