Microencapsulation of phenobarbital by spray polycondensation.

A new method for the microencapsulation of solids is described. It is based on the polycondensation of amphiphilic and, thus, tensioactive precondensates on a melamine-formaldehyde base on the surface of suspended particles during spray drying. A film-forming agent, preferably one that reacts chemically with the resin, is indispensable for spray drying and also for the formation of an efficient membrane around the drug particles. The resulting microcapsules are essentially spherical and have, after appropriate curing, a sustained-release effect in vitro. The factors that most influence the formation and properties of the microcapsules are the composition (qualitative and quantitative), pH, and viscosity of the suspension.