Characterization of carbamazepine-Gelucire 50/13 microparticles prepared by a spray-congealing process using ultrasounds.

In this work, the utilization of a spray-congealing technique using a new ultrasonic atomizer to prepare enhanced-release, solvent-free microspheres of carbamazepine (CBZ)-Gelucire 50/13 in different drug-to-polymer ratios was considered. Scanning electron microscopy analysis showed that it was possible to obtain spherically shaped and nonaggregated microparticles; the prevalent particle size was in the range 150-250 microm and the microspheres had a good encapsulation efficiency (> 90% in the prevalent size fraction). The in vitro dissolution tests displayed a significant increase of the CBZ dissolution rate from microspheres compared with pure drug and to drug-Gelucire 50/13 physical mixture. Differential scanning calorimetry, hot stage microscopy, X-ray powder diffractometry, and diffuse reflectance Fourier transform infrared spectroscopy demonstrated phase stability of the original polymorph of CBZ in all the systems; moreover, no interactions between the drug and Gelucire 50/13 were found. The results of this study suggested that the spray-congealing technique using the ultrasonic atomizer could be considered as a new and interesting method to enhance the dissolution rate of a poorly water-soluble drug as CBZ. Copyright 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association.