PREPARATION AND STUDY OF THE CHARACTERISTICS OF DITHRANOL-POLYVINYLPYRROLIDONE COEVAPORATES

Dithranol:polyvinylpyrrolidone (Di:PVP) 1:2, 1.4, 1:9, 1:14, 1:25 and 1:40 coevaporates were prepared to increase the aqueous dispersibility of this hydrophobic and water insoluble drug, used for the topical tr eatment of psoriasis. The coevaporates contained small crystals of Di as well as nanoparticles of Di, embedded in the PVP matrix. This submi cron fraction increased with increasing PVP, up to a DI:PVP ratio of 1 :25. The coevaporates exhibited a hydrophilic character, allowing easy dispersion in water. This dispersion contained very small particles o f submicron size (average diameter 0.1 mu m) and an insoluble part con sisting of small Di crystals. When the insoluble fraction nias elimina ted by filtration, an aqueous stable colloidal dispersion of Di was ob tained. This extreme particle size reduction, combined with an enhance d hydrophilic character should provide Di with interesting characteris tics for topical treatment of psoriasis. (C) 1998 Elsevier Science B.V . All rights reserved.