Modified release dosage form refers to a measured delay on release of drug after it is consumed orally. It prolongs the effect of the drug so that multiple doses are not necessary. There are several terms available to describe “Timed Release Drugs” such as sustained release, prolonged release and delayed response and controlled release. Sustained forms are designed to release the drug at a specified rate to maintain concentration with minimum side effects. (Liposomes represents one form of such release control. For information on liposome measurements please see Microtrac.com Applications Note SL-AN-07 “High-Concentration Liposome and Micelle Suspensions: Measurement by Dynamic Light Scattering”.). The sustained release provides immediate release of drug for rapid effect and then is followed by slow release of the remaining dosage. Levels of drug are prolonged, but concentrations are not maintained constant. On the other hand, Controlled Release is designed to provide constant release and maintain concentrations over time and apply therapeutic action at a specific site. Sustained release can be considered Controlled release depending on the purpose and properties.
