The conventional oral dosage forms have some drawbacks like poor bioavailability, first pass metabolism, of drug, frequent dosing which may leads to patient non compliance. The transdermal drug delivery system is one of the type novel drug delivery system which overcome the problems arises from conventional dosage forms. A transdermal patch is medicated adhesive patch these is place on the surface of skin and these deliver a specific dose of drug medicament through the skin and in to bloodstream. It also helps to healing to a mild injured surface of skin. An advantage of a transdermal drug delivery route over other types of medication delivery such as oral, topical, intravenous, intramuscular, etc. is that the patch provides a controlled release of the medication into the patient and it gives painless drug delivery to the patient over intravenous route of drug administration. Its having some disadvantage it permit only drug having smaller molecular size. This review gives valuable information about the TDDS like its advantages, disadvantages, types of TDDS, different methods for formulation of transdermal patches, different evaluation of transdermal patches. Different methods for preparation of transdermal patches. Skin permeation enhancement techniques have been developed to improve the bioavailability of drug.
