Time-controlled pulsatile delivery systems for bioactive compounds.

In the body under physiological conditions, many vital functions are regulated by pulsed or transient release of bioactive substances at a specific time and site. Thus, to mimic the function of living systems, it is important to develop new drug delivery devices to achieve pulsed delivery of a certain amount of a bioactive compound at predetermined time intervals. The ability to deliver bioactive compounds and/or therapeutic agents to a patient in a pulsatile or staggered release profile has been a major goal in drug delivery research over the last two decades. The plasma peak is obtained at an optimal time by timing the drug administration. The number of doses per day can be reduced. Based on the relevance of potential therapeutic applications, a variety of design strategies have been formulated in the pursuit of pulsatile release. Overall, these systems can be categorized into reservoir, capsular and osmotic devices. In this review article, several types of dosage forms, including microparticles, coarse particulates, large solid implants, hydrogels, osmotic pumps and liposomes, for time-controlled pulsatile release are discussed. This review describes the recent patents related to pre-programmed delivery systems, such as systems with eroding, soluble or rupturable barrier coatings, and systems with capsular structures.