Controlled drug delivery systems

Controlled drug release technology has attracted increasing interest over recent years and already, devices incorporating this technology have been introduced into clinical use in several fields of medicine. Controlled release preparations can maintain the drug in the desired therapeutic range by means of a single dose; localize delivery of the drug to a particular body compartment, which lowers the systemic drug level; reduce the need for follow-up care; preserve medications that are rapidly destroyed by the body; and increase patient comfort and compliance. A useful classification of controlled-release system based on the mechanism controlling the drug release is as follows: diffusion controlled systems (membrane (reservoir) systems and matrix (monolithic) systems), chemically controlled systems (bioerodible systems and drug-polymer conjugates), solvent activated systems (osmotically controlled systems and swelling controlled systems), self and externally controlled systems (systems utilizing enzymes, and magnetically or ultrasonically triggered systems).