Evaluation of spray-drying as a method to prepare microparticles for controlled drug release

The possibility to obtain microcapsules or microspheres for controlled release by spray-drying is evaluated. Drugs of different solubilities like theophylline and sodium sulfamethazine, with Eudragit RS as coating polymer, are chosen. The polymer is used, either dissolved in an hydroalcoholic solution or suspended (pseudolatex) in water, in different weight ratios with the drug. The obtained solution or suspension is spray-dried. Scanning electron microscope analysis of the powders reveals no sign of microencapsulation. Moreover, only a fraction of the particles has a spherical shape. For each spray-dried powder, a part of the obtained particles is compressed into tablets, and the rest is stored. Dissolution studies in distilled water at 37 C are performed on powders and tablets. While the uncompressed microparticles do not give any controlled release, the tablets show an ability in slowing down drug delivery greater than the one obtained with the traditional methods.