[Long-term controlled release of drugs]

The surveys of long-term controlled drugs supply systems have become recently one of more important branches of pharmacy. Many systems were elaborated. The systems differ from each other by the mechanism and time of drug release and the way of administering it. A large number of polymers have been developed with the capability of controlling the release rate over a long period of time (from 12 hr to 5 years). The programmed delivery of drugs offers advantages over conventional methods of administration. Controlled release drug delivery systems include oral, transdermal, injectable, implanted, intrauterine and intravaginal systems. In this paper different sustained-release systems in current use are reviewed.