ABSTRACT
Microencapsulated and particulate systems for drug delivery have found wide application in pharmaceutics; initially for external use as creams and ointments, later for subcutaneous drug delivery, and in oral and intravenous administration (1). The release of drugs from microencapsulated systems, including micro-and nanocapsules, micro-and nanospheres, micro-and nanoparticles, and emulsion droplets, has been extensively reviewed (1-4). Release mechanisms are commonly inferred from kinetic measurement data of microencapsulated drug delivery systems by indirect methods based on the effects of solvent, buffer, agitation rate, or other variables. Drug-release data have a number of potential applications. At the simplest level, the data can be used for quality control purposes to ensure the constancy of behavior of a manufactured product. It can further be used to try to understand the physicochemical structure of the delivery system and the drug-release mechanism; however, this normally requires the applying of the data to that computed for a model of the drug delivery system (5-16). Finally, such data can be used in an attempt to predict the likely behavior of the system in vivo (17-29). Drug release or dissolution testing is an essential requirement for the development, establishment of in vitro dissolution and in vivo correlation (IVIVC), and registration and quality control of dosage forms. Under certain conditions, in vitro drug release can be used as a surrogate for the assessment of bioequivalence (30).
