HYDROGEL DEVICE FOR SLOW RELEASE OF ACTIVE AGENTS

An active agent containing controlled release diffusion jevice comprising a swellable hydrogel matrix in the non-swollen state, interpenetrated with an active agent solute laving a stable concentration distribution increasing in a gradient normal to the surface of the device and between the surface and the core thereof, said gradient being in the form of a substantially continuous, inflection point containing, sigmoidal curve, such that the device, when placed in an aqueous hydrogel swelling environment, releases said active agent in a controlled continuous manner by diffusion for a predetermined period of time, a method of preparing such a device, and the use thereof to release an active agent into the intended environment of use.