preparation and evaluation of a liquid sustained-release drug delivery system for theophylline using spray-drying technique

in recent years, great efforts have been devoted to the design of drug delivery systems. many polymeric excipients have been studied in order to make drug release fit the desired profiles. the aim of this work was to design a theophylline oral suspension, as sustained release pharmaceutical preparation in order to decrease the plasma level fluctuations and adverse effects of theophylline. microspheres were prepared by a spray-drying technique using theophylline and two polymers, ethyl cellulose and hydroxy propyl methyl cellulose phthalate (hpmcp) in different solvents and ratios of polymer to drug. the spray-dried microparticles were characterized in terms of shape and drug release. they were formulated in suspensions and evaluated by dissolution and stability studies. the type of polymer and spray dryer feed solution had a major impact on the in vitro performance and release of theophylline from microcapsules and suspensions. only in the case of the microcapsules derived from hpmcp in acetone (as a solution feed) and ethyl cellulose in methylene chloride (as a suspension feed) in all of polymer to drug ratios, perfect spherical microcapsules with sustained release behavior were observed. suspensions prepared from hpmcp microcapsules derived in acetone and ethyl cellulose microcapsules in methylene chloride met the requirements of usp for sustained release drug delivery systems. this report documents the suitability of these polymeric suspensions for encapsulated theophylline with a controlled release rate.