Microparticle size control and glimepiride microencapsulation using spray congealing technology

Drug-free microparticles were prepared using a spray congealing process with the intention of studying the influence of processing parameters. By varying the atomizing pressure and liquid feed rate, microparticles with median sizes (d((0.5))) from 58 to 278 microm were produced, with total process yields ranging from 81% to 96%. An increased liquid feed rate was found to increase microparticle size, and higher atomizing pressures were found to decrease microparticle size. Greater change in microparticle size was achieved by varying atomizing pressure, which can be considered a dominant process parameter regarding microparticle size. In addition, microparticles with glimepiride, a model poorly water-soluble drug, were prepared by spray congealing using three different hydrophilic meltable carriers: Gelucire 50/13, poloxamer 188, and PEG 6000. Spherical microparticles with relatively smooth surfaces were obtained, with no drug crystals evident on the surfaces of drug-loaded microparticles. XRPD showed no change in crystallinity of the drug due to the technological process of microparticle production. All glimepiride-loaded microparticles showed enhanced solubility compared to pure drug; however, Gelucire 50/13 as a carrier represents the most promising approach to the dissolution rate enhancement of glimepiride. The influence of storage (30 degrees C/65% RH for 30 days) on the morphology of glimepiride/Gelucire 50/13 microparticles was studied, and the formation of leaf-like structures was observed (a "blooming" effect).