Transdermal Drug Delivery

Transdermal drug delivery systems (TDDS), also known as “‘patches,”’ are dosage forms that provide a controlled release of therapeutically effective amount of drug across a patient’s skin. This chapter discusses the detailed aspects regarding concept of skin, drug penetration and drug kinetics, formulation and evaluation of TDDS, and its applications. From decades, TDDS has drawn deliberate consideration for either local or systemic drug delivery, owing to its unique advantages, like prolonged therapeutic effect, avoidance of first-pass metabolism, and easy termination of therapy. The stratum corneum poised the barrier; however, appendageal and transepidermal routes were identified for drug transport via skin. The basic components of TDDS are rate-controlling membrane, drug, penetration enhancers, adhesives, backing laminates, release liner, etc. Different architecture of TDDS classifies them as reservoir, matrix, and microreservoir system. Quality of prepared TDDS may be evaluated by evaluations that include physicochemical properties, in vitro drug release and skin permeation studies, and adhesive property evaluations, etc. Lastly, chapter furnishes information of various approaches to achieve transdermal drug delivery using novel formulation strategies like nanoparticles, lipid vesicles, and physical strategies such as iontophoresis, sonophoresis, and microneedles. Based on these approaches, numerous transdermal products are now available in the market for clinical applications.