Controlled-release drug delivery systems CrDDSs

Based on the technical sophistication of the controlled-release drug delivery systems (CrDDSs) that have been marketed so far, or that are under active development, the CrDDSs can be classified (Fig. 2) as follows ... 

The controlled-release drug delivery systems outlined here have been steadily introduced into the biomedical community since the middle of the 1970s. There is a growing belief that many more of the conventional drug delivery systems we have been using for decades will be gradually replaced in the coming years by these CrDDSs. 

In this group of CrDDSs, the release of drug molecules from the delivery systems has been preprogrammed at a specific rate profile. This is accomplished by system design, which controls the molecular diffusion of drug molecules in and/or across the barrier medium within or surrounding the delivery system. Pick s laws of diffusion are often followed. These CrDDSs can further be classified as follows ... 

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