first pass metabolism

Release of drugs via the skin has been always a challenging part for research due to obstacle properties shown by the outermost layer of skin stratum corneum. In the previous two decades, the transdermal drug delivery system has turn into a established technology that offers important clinical repayment over additional dosage forms. Because transdermal drug delivery offers controlled as well as programmed rate of release of the drug into the patient, it is capable to maintain steady state blood concentration. It’s a advantageous form of drug delivery because of the apparent advantages e.g. suitable and pain-free self-administration for patients, prevention of hepatic first-pass metabolism and the GI tract for poorly bioavailable drugs than other routes of deliverance.Thepresent article reviews the choice of drug candidates and polymers, advantages, disadvantages of formulation, design and the methods of evaluation, augmentation techniques based on drug/vehicle optimization such as selection of drug, prodrugs and ion pairs, supersaturated drug solutions, vesicles, liposomes, particles and complexations. This review also emphases on the recent innovations in TDDS, which be able to used for the research and improvement of pharmaceutical dosage form intended for transdermal drug delivery.

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.