Modified release dosage forms have acquired a great importance in the current pharmaceutical research. It denotes a formulation of a medicinal agent that releases the active ingredients over several hours, in order to maintain a relatively constant plasma concentration of the drug. In addition, sustained and controlled release devices are not applicable in some cases like time-programmed administration of hormones and many drugs. The living systems are predictable dynamic resonating systems which require different amounts of drug at expected times within the circadian cycle.  Pulsatile drug delivery system has fulfilled this requirement. This system is such a system where drug is released suddenly after well-defined lag time or time gap according to circadian rhythm of disease states. No drug is released from the device within this lag time. This method is good for the drugs with extensive first pass metabolism and targeted to specific site in the intestinal tract. Pulsatile drug delivery system classified as time controlled pulsatile release, stimuli induced, chemical stimuli induced pulsatile systems, external stimuli pulsatile release etc.

Keywords – lag time, pulsatile, time controlled, first pass metabolism, stimuli induced