ABSTRACT
The importance of controlled drug delivery systems that release bioactive components over an extended period of time has long been recognized in the pharmaceutical field. Of the many routes of drug delivery, oral administration remains the most convenient and commonly em ployed means for introducing drugs to the systemic circulation. Recent advances in controlled release technology have made it possible to release drugs at a constant rate for days to years. Application of such controlled release technology to oral drug delivery, however, has been lim ited because the actual time for effective drug delivery is restricted by the gastrointestinal tran sit time, which typically ranges from several hours to 12 h depending on various factors (1). Thus, unless a drug has a long half-life, it needs to be administered a few times a day.
