Efavirenz dissolution enhancement V - A combined top down/bottom up approach on nanocrystals formulation

Efavirenz is one of the most commonly used drugs in HIV therapy. However the low water solubility tends to result in low bioavailability. Drug nanocrystals, should enhance the dissolution and consequently bioavailability. The aim of the present study was to obtain EFV nanocrystals prepared by an antisolvent technique and to further observe possible effect, on the resulting material, due to altering crystallization parameters. A solution containing EFV and a suitable solvent was added to an aqueous solution of particle stabilizers, under high shear agitation. Experimental conditions such as solvent/antisolvent ratio; drug load; solvent supersaturation; change of stabilizer; addition of milling step and solvents of different polarities were evaluated. Suspensions were characterized by particle size and zeta potential. After freeze- dried and the resulting powder was characterized by PXRD, infrared spectroscopy and SEM. Also dissolution profiles were obtained. Many alterations were not effective for enhancing EFV dissolution; some changes did not even produced nanosuspensions while other generated a different solid phase from the polymorph of raw material. Nevertheless reducing EFV load produced enhancement on dissolution profile. The most important modification was adding a milling step after precipitation. The resulting suspension was more uniform and the powder presented grater enhancement of dissolution efficacy.