Oral dosage forms are known to provide a zero order or first order release in which the drug is released at a substantially steady rate of release per unit of time. However, there are instances where maintaining a constant blood level of a drug is not desirable. In such cases a pulsatile drug delivery may be more advantageous. Pulsatile drug delivery systems can be classified into site-specific systems in which the drug is released at the desired site within the intestinal tract (e.g., the colon), or time-controlled devices in which the drug is released after a well-defined time period. Environmental factors like pH or enzymes present in the intestinal tract control the release of a site-controlled system whereas the drug release from time-controlled systems is controlled primarily by the delivery system and not by the environment. The delayed liberation of orally administered drugs has been achieved through a range of formulation approaches, including single or multiple unit systems provided with release-controlling coatings, capsular devices and osmotic pumps. Our aim in this review is to outline the rational and prominent design strategies behind site-specific oral pulsatile delivery. The present article provides a good patent review regarding the Site Specific Chronotherapeutic Drug Delivery Systems.
Keywords: Pulsatile release, colon specific systems, lag time, burst release, enteric coating, methylmethaacrylate copolymers
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