Transdermal Drug Delivery Systems: A Systematic Review

Abstract

Transdermal drug delivery systems (TDDS) have emerged as an effective and patient-friendly alternative to conventional oral and parenteral drug administration routes. By delivering drugs across the skin into systemic circulation, TDDS offer several advantages, including avoidance of first-pass hepatic metabolism, sustained and controlled drug release, improved bioavailability, and enhanced patient compliance. The stratum corneum, however, acts as a major barrier to drug permeation, limiting the transdermal delivery of many therapeutic agents. To overcome this challenge, various strategies such as chemical penetration enhancers, vesicular carriers (ethosomes, transfersomes, invasomes), microneedles, iontophoresis, sonophoresis, and advanced patch designs have been developed. Recent advances in materials science and nanotechnology have further expanded the scope of TDDS, enabling the delivery of macromolecules, peptides, and vaccines. This review provides a comprehensive overview of the principles of transdermal drug delivery, skin anatomy and permeation pathways, formulation components, and different generations of transdermal systems. Current commercial products, regulatory considerations, and recent innovations in TDDS are also discussed. Despite existing challenges related to skin irritation, dose limitations, and inter-individual variability, ongoing research continues to improve the efficacy and applicability of transdermal systems. Overall, TDDS represent a promising platform for controlled and targeted drug delivery in modern therapeutics.