Pulsatile drug delivery system using core in cup approach: a review
Oral controlled drug delivery systems represent the most popular form of controlled drug delivery systems for the obvious advantages of oral route of drug administration. Such systems release the drug with constant or variable release rates. Pulsatile drug delivery system (PDDS) can be defined as a system where drug is released suddenly after a well defined lag time according to the circadian rhythm of the disease. PDDS can be classified according to the pulse regulation of drug release into three main classes; time controlled pulsatile release (single or multiple unit system) internal stimuli induced release and external stimuli induced pulsatile release systems. Pulsatile delivery is generally intended as a release of the active ingredient that is delayed for a programmable period of time to meet particular chronotherapeutic needs and, in the case of oral administration, also target distal intestinal regions, such as the colon. Most oral pulsatile delivery platforms consist in coated formulations wherein the applied polymer serves as the release controlling agent. When exposed to aqueous media, the coating initially performs as a protective barrier and, subsequently, undergoes a timely failure based on diverse mechanisms depending on its physico chemical and formulation characteristics.