ABSTRACT
This chapter focuses on the mechanisms of solute release, factors influencing the release process, and pharmaceutical applications. It discusses plastic monolithic dispensers used in the agricultural and pesticide fields. Monolithic devices have been prepared using hydrophilic polymers, such as cross-linked Polyacrylamide and polyvinylpyrrolidone, hydroxyethylmethacrylate, polyvinyl alcohol, and ethylenevinyl acetate copolymers to release proteins and hormones. The recognition that drugs can be released from polymeric devices has resulted in a proliferation of research in the area of controlled delivery of bioactive agents. The size and shape of the diffusing molecule, the degree of polymer crystallinity, and polymer chain-chain interactions and flexibility will affect the polymers ability to form a hole large enough to accommodate the penetrating molecule. The polymer-water partition coefficient comes into play when transfer from the polymer phase to the eluting solvent occurs. In the case of membrane transport, the product of the partition coefficient and diffusion coefficient defines the permeability constant.
