ORGANIC SOLVENT-FREE POLYMERIC MICROSPHERES PREPARED FROM AQUEOUS COLLOIDAL POLYMER DISPERSIONS BY A W O-EMULSION TECHNIQUE/

Polymeric microspheres were prepared from water-insoluble polymers by a novel technique without the use of organic solvents. Aqueous colloid al polymer dispersions (latexes or pseudolatexes) were emulsified into a heated external oil phase to form a w/o emulsion. The colloidal pol ymer particles fused (coalesced) into homogeneous polymeric microspher es at temperatures above the minimum him formation temperature upon re moval of water. The formation of the microspheres was affected by the glass transition temperature of the polymer, the type of oil and surfa ctant, the heating temperature and rime, and the addition of plasticiz ers. Plasticizers had to be added to colloidal dispersions with high m inimum film formation temperatures. The resulting microspheres were sp herical with a smooth surface and non-agglomerated. The particle size could be varied between 5 and 250 mu m. Water-soluble compounds such a s propranolol HCl could be entrapped with drug loadings up to 40% with in the microspheres by dissolving the drug in the aqueous polymer disp ersion prior to the emulsification step. The drug release was sustaine d over a 6-h period with microspheres prepared with the acrylic pseudo latex, Eudragit RS 30D.