Controlled Release

Controlled-release technologies are developed to deliver drugs, proteins, pesticides, fragrances, and other bioactive agents at a controlled rate for a desired time period to maintain a constant and effective level of an active ingredient. Controlled-release formulations provide greater efficacy, convenience, and improved safety by maintaining optimal concentrations of the active ingredient. Many controlled-release technologies operate by diffusion of the active ingredient or water through a rate-controlling membrane and can be classified into four categories: (1) reservoir types, (2) matrix systems, (3) swelling-controlled systems, and (4) osmotic systems.

In reservoir (membrane) systems, the bioactive agent is either encapsulated by two semipermeable membranes or core containing the active ingredient is surrounded by a semipermeable membrane. Diffusivity and solubility of the active ingredient in the membrane are two key parameters that influence the rate of diffusion through the...