Transdermal Patches: A Comprehensive Review

Transdermal drug delivery systems (TDDS) have emerged as a promising alternative to conventional drug administration methods due to their ability to deliver drugs in a controlled and sustained manner through the skin. These patches offer multiple advantages, including improved patient compliance, avoidance of gastrointestinal degradation and hepatic first-pass metabolism, and sustained plasma drug levels. This review comprehensively discusses the fundamentals of transdermal drug delivery, including skin structure and permeability, formulation strategies, mechanisms of drug transport, and types of transdermal patches such as reservoir, matrix, and drug-in-adhesive systems. The role of various formulation components—polymers, penetration enhancers, plasticizers, and adhesives—is critically analyzed for their impact on drug release and skin permeation. Recent advances in TDDS are also highlighted, focusing on microneedle arrays, nanoformulations, and iontophoresis, which are designed to overcome the limitations of traditional patches. Moreover, the review outlines evaluation parameters, regulatory considerations, and challenges like skin irritation, drug dose limitations, and inter-individual variability. With continuous innovation, TDDS are poised to play a significant role in future pharmaceutical care by enabling non-invasive, targeted, and patient-friendly drug delivery.