Plasma enhanced chemical vapor depositions to encapsulate crystals in thin polymeric films: a new approach to controlling drug release rates.

An RF plasma discharge was employed to deposit thin polymeric films on drug particles. This study utilized acetylsalicylic acid (aspirin) crystals and allyl alcohol as polymerizable monomer for this new approach to controlling drug release rates. Release rates of coated and uncoated particles were measured in aqueous solution at a pH of 1.0. The drug release rates could be varied over wide ranges by appropriate control of the polymeric films. These controls included film composition, extent of polymer cross-linking and film thickness. A 360 degrees rotating plasma reactor was employed to provide effective agitation and mixing of the drug particles during the coating operation. The plasma discharge was operated in a pulsed mode to provide improved control of the polymer film compositions and, at the same time, minimize undesirable decomposition of drug molecules. Overall, the results obtained clearly indicate that the pulsed RF plasma coating process developed represents a viable, one-step, solventless route to controlled drug release.