Controlled release excipients have become major research components in the pharmaceutical industry. Controlled release excipients give the formulator the ability to carry APIRs to a specific site in the body. This benefit increases the drugs bioavailability and reduces side effects. Controlled-release behavior can be achieved using polymer coatings on solid dosage forms or by the incorporation of various types of polymer matrix systems, enzyme-activated systems, or systems that respond to changes in physical conditions within the formulation. Controlled release mechanisms can include dissolution, diffusion, osmotic pressure, maintaining a hydrologic or hydrodynamic balance, and ion exchange.