Fluidized bed film coating of an interactive powder mixture to produce microencapsulated 2-5 microns particles

Previous work has shown an interactive (ordered) powder mixture, formed from 2-5 microns salicylic acid and a coarse spray-dried sugar, is stable when fluidized. The micronized material adheres to the carrier during fluid bed air suspension and may be film coated with a polymer. This process offers a novel method of microencapsulating very fine particulates, providing a way of manufacturing enteric-coated and sustained release microdose drug delivery systems. Different processing conditions were used in an attempt to optimize the retention of micronized model drug beneath the film. The effect of altering the following variables was investigated; polymer spray rate, addition of a third component which adhered to the binary adhesion units, and different materials of construction for the mixer used to form the interactive mixture. The microencapsulated adhesion units retained 90-95% of the micronized model drug. A statistical evaluation of the content uniformity showed that a very uniform dispersion was formed (CV less than 5%, 99% confidence). Multilayer film-coated adhesion units were also produced using a sequence of mixing and coating operations. This process offers a method of film coating microdose quantities of a drug, to produce a free flowing product, possessing excellent content uniformity.