ABSTRACT
Reservoir systems, widely used for oral-controlled or sustained drug release, consist of a polymer coating on solid substrates (reservoir), such as powders, beads, granules, capsules, or tablets. Latex or pseudolatex presentations of water-insoluble polymers have largely superseded the use of organic solvents for applying such coatings. Aqueous polymer dispersions are preferred on environmental and safety grounds as solvents are not used during the coating process. These dispersions or aqueous polymer emulsions may be prepared by emulsion polymerization of a monomer (latex) or by emulsication of a polymer (pseudolatex). Dispersions of biopolymer derivatives, such as the cellulosics, can only be prepared as pseudolatices.
