Osmotic pumping mechanism, drug-release from

Jensen JL, Appel LE, Clair JH, Zentner GM. Variables that affect the mechanism of drug release from osmotic pumps coated with acrylate/methacrylate copolymer latexes. / Pharm Sci 1995 84 530-533. 

The driving force for drag release from a pump is a pressure difference that causes the bulk flow of a drag, or drug solution, from the device at a controlled rate. This is in contrast to the polymeric controlled release systems described above, where the driving force is due to the concentration difference of the drag between the formulation and the surrounding environment. Pressure differences in an implantable pump can be created by osmotic or mechanical action, as described below. 

The controlled release of drugs can be realised with many types of active devices, such as mechanical and osmotic pumps, systems of controlled diffusion, chemically-controlled systems composed from bio- or non-biodegradable polymers, magnetically-controlled systems, and not in the last instance chemomechanical systems. Figure 4.39 [136, 137]. 

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