Transdermal Drug Delivery: Innovations, Challenges, and Future Directions

Abstract

Transdermal drug delivery systems (TDDS) are increasingly utilized to administer drugs across the skin for systemic effects. This review discusses the skin structure and the mechanism of drug penetration through different skin layers, emphasizing the physicochemical properties required for effective transdermal permeation. We explore various types of TDDS, such as matrix, reservoir, and drug-in-adhesive systems, detailing their composition, operation, and the role of excipients like permeation enhancers. The kinetics of drug permeation and the impact of chemical enhancers on this process are analyzed. Additionally, the design and evaluation methods of TDDS, including physicochemical stability, in vitro, and in vivo performance assessments, are extensively reviewed. By enhancing the understanding of TDDS components and mechanisms, this article contributes to the development of more effective transdermal therapeutic solutions.