Transdermal Drug Delivery Systems: A Focused Review of Physical Methods of Permeation Enhancement

The skin is the largest organ of the body and has been widely utilized as a route of drug delivery. Transdermal drug delivery systems (TDDS) offer numerous advantages over conventional routes such as bypassing hepatic first-pass metabolism, achieving controlled plasma levels, and improving patient compliance. This paper reviews the physical methods of permeation enhancement including iontophoresis, ultrasound, microneedles, and other device-assisted strategies. Schematic illustrations are included for better understanding.