Transdermal Drug Delivery System

A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into systemic circulation. Often, this promotes healing to an injured area of the body. 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, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. Transdermal drug delivery offers controlled release of the drug into the patient, it enables a steady blood level profile, resulting in reduced systemic side effects and, sometimes, improved efficacy over other dosage forms. The main objective of transdermal drug delivery system is to deliver drugs into systemic circulation through skin at predetermined rate with minimal inter and intrapatient variations. Transdermal drugs are self- contained, discrete dosage form. It delivers a drug through intact skin at a controlled rate into the systemic circulation. Delivery rate is controlled by the skin or membrane in the delivery system. It is a sophisticated complex drug delivery system which is difficult to formulate. It requires specialized manufacturing process/equipment. The materials of construction, configuration and combination of the drug with the proper cosolvent, excipient, penetration enhancer, and membrane are carefully selected and matched to optimize adhesive properties and drug delivery requirements. Several transdermal products and applications include hormone replacement therapy, management of pain, angina pectoris, smoking cessation and neurological disorders such as Parkinson's disease. Formulated to deliver the drug at optimized rate into the systemic circulation should adhere to the skin for the expected duration should not cause any skin irritation and/or sensitization, enhancing bioavailability via bypassing first pass metabolism, minimizing pharmacokinetic peaks and troughs, improving tolerability and dosing increasing patient compliance in continuous delivery. This review article provides an overview of TDDS, its advantages over conventional dosage forms, Limitations, various components of Transdermal patches, types of Transdermal patches, methods of preparation and Ideal requirements for TDDS, regulatory issues over transdermal drug delivery, its physicochemical methods of evaluation, therapeutic uses and recent advances in transdermal drug delivery system.1