Review on Transdermal Drug Delivery System and Herbal Transdermal Patches

Abstract

Transdermal drug delivery system (TDDS) has emerged as one of the most reliable non-invasive routes of drug administration, offering an alternative to oral and parenteral dosage forms. By delivering therapeutic agents across intact skin directly into the systemic circulation, transdermal patches bypass hepatic first-pass metabolism, minimize gastrointestinal degradation, sustain plasma drug concentrations, reduce dosing frequency and improve patient compliance. This review presents a detailed account of the anatomy of skin as a delivery portal, the historical evolution of transdermal technology, the rationale, advantages and limitations of TDDS, the mechanisms and pathways of percutaneous absorption, the physicochemical and physiological factors that govern permeation, the essential components of a patch, the various design approaches (reservoir, matrix, drug-in-adhesive and micro-reservoir systems), chemical and physical permeation-enhancement strategies, methods of fabrication, pharmacopeial evaluation parameters and currently marketed transdermal products.

The second half of the review focuses specifically on herbal transdermal patches, an emerging green alternative in which standardized plant extracts and phytoconstituents are incorporated into a polymeric matrix instead of, or in combination with, synthetic drugs. Herbal transdermal systems combine the traditional therapeutic wisdom of medicinal plants with the controlled-release engineering of modern TDDS, offering reduced toxicity, wider patient acceptance and lower manufacturing cost. The review discusses commonly employed herbal drugs, natural polymers and permeation enhancers, formulation strategies unique to phytopharmaceuticals, evaluation protocols, current challenges such as standardization and stability, and recent advances including nanocarrier-based herbal patches. The review concludes that although considerable technological progress has been made, systematic pharmacokinetic and clinical validation of herbal transdermal systems remains an important area for future research.