lag time

In the recent years the pulsatile drug release systems are gaining growing interest. The pulsatile drug release where the drug is rapidly released after the well defined lag-time could be advantageous for many drugs or therapies. The sustained & controlled release devices are not applicable in some of the cases like the time-programmed administration of the hormones & many drugs. The living systems are the predictable dynamic resonating systems which require different amounts of drug at the expected times within the circadian cycle. The pulsatile drug delivery system has fulfilled this requirement. This system is such a system where the drug is released suddenly after the well-defined lag time or the time gap according to the circadian rhythm of the disease states. No drug is released from the device within this lag time. This method is good for the drugs with the extensive first pass metabolism & targeted to the specific site in the intestinal tract. The current article focuses on the necessities of pdds, diseases requiring PDDS, classification of pulsatile drug delivery system, current situation and future scope& marketed technologies of pulsatile drug delivery system.

The objective of present investigation was to prepare a chrono-modulated drug delivery system for Naproxen sodium to meet chrono pharmacological needs of Arthritis. Press coated tablets is a novel oral pulsatile release drug delivery system in which  the drug is released after certain period of lag time generally due to the erosion of barrier layers. Tablets were prepared by direct compression method. The core tablet was formulated using super-disintegrants like sodium starch glycolate, crosspovidone and crosscarmellose sodium. Whereas, the barrier layer contains polymers like carrageenan gum (Viscarin GP-209), xanthan gum in different concentrations and lactose anhydrous as channeling agent for maintaining lag time. The drug-excipient compatibility was confirmed by using FTIR, predicted that there was no chemical interactions between the drug and excipients. The tablets prepared were evaluated for micromeritic properties. In-vitro drug release studies were carried out using pH 1.2 buffer for initial 2hrs and in pH 7.4 phosphate buffer for remaining 10hrs. All the formulations followed first order release kinetics. From the obtained results it was found that the F9 formulation of immediate release core tablets (10% of Crosspovidone) showed optimized in vitro disintegration time and wetting time respectively. In case of press-coated tablets PCT 8 formulation with hydrophilic polymers 19.2% carrageenan gum, 19.2% xanthan gum and 7.69% lactose anhydrous as channeling agent has shown 6hrs of lag time is considered as optimum formulation and is successful in resisting different RPM pressures for designing into pulsatile delivery for treatment of Arthritis.

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.

The aim of present investigation was to develop press coated tablet for pulsatile drug delivery of lornoxicam using hydrophilic and hydrophobic polymers. The drug delivery system was designed to deliver the drug at such a time when it could be most needful to patient of rheumatoid arthritis. The press coated tablets containing lornoxicam in the inner core was formulated with an outer shell by different weight ratio of hydrophobic polymer (ethyl cellulose) and hydrophilic polymers (sodium alginate). The release profile of press coated tablet exhibited a lag time followed by burst release, in which outer shell ruptured into two halves. The effect of formulation composition on the barrier layer comprising both hydrophobic and hydrophilic excipients on the lag time of drug release was investigated. It was observed that lag time decreases with increasing concentration of sodium alginate. The optimized formulation (F5) comprised 10: 90%w/w concentration ratio of sodium alginate: Ethocel 10 cps with a 245 mg coating weight, and showed a desired lag time of 308 minutes, which mimics the fluctuating symptoms of rheumatoid arthritis, followed by rapid release of lornoxicam.