An Insight into delivery of drug through The Skin: Transdermal Drug Delivery system

In the recent days about 75% of the drugs taken orally are does not show the desired therapeutic effect. Oral conventional dosage forms have several disadvantages such as poor bioavailability due to hepatic first pass metabolism and tendency to produce rapid blood level spikes (Both high and low). Thus, rapid drug levels in the plasma leads to a need of high and/or frequent dosing, which can be both uneconomical and inconvenient. To overcome such disadvantages transdermal drug delivery system was developed. TDDS is such a delivery system which has been explored extensively over the last two decades, with therapeutic success. Transdermal drug delivery systems (TDDS) are the drug delivery systems which involves transportation of drug to epidermal and dermal tissues of the skin for local therapeutic action while major fraction of the drug is transported into the systemic blood circulation. Topical administration of therapeutic agents offers vast advantages over conventional oral and invasive methods of drug delivery. Some of the advantages of transdermal drug delivery include limitation of hepatic first pass metabolism, enhancement of therapeutic efficiency and maintenance of steady state plasma level concentration of the drug. This study includes a brief overview of TDDS, its advantages over conventional dosage forms, drug delivery routes across human skin, permeation enhancers, and classification, formulation, methods of preparation and evaluation of transdermal patches.