US Patent 6960357 Chemical delivery device

The invention provides a controlled release dissolution and diffusion devices which can deliver an active ingredient at a constant or controlled-variable rate comprising an active ingredient and dissolution modifiers and/or an insoluble matrix. The compressed core is coated, except for at least one exposed face, with a coating containing an insoluble polymer or a mixture of an insoluble polymer and pore-forming elements said pore-forming elements having a dissolution rate slower that the release rate so that the pore formation is completed after release of the active ingredients and the residual inert structures disintegrate.