V3I10P64

Transdermal Drug Delivery Systems: A Review of Skin Permeation, Formulation Approaches and Current Challenges

Shaik Moulali¹*, Shabana Parveen Begum²

Abstract

Delivering a drug through the skin and into the systemic circulation is an attractive alternative to swallowing a tablet or receiving an injection. A transdermal patch avoids first-pass metabolism, keeps plasma levels fairly steady, and can be removed if side effects appear. Even so, only a modest number of molecules have reached the market in this form, mainly because the outermost skin layer, the stratum corneum, is an excellent barrier. This review summarises the structure of the skin and the routes by which molecules cross it, the physicochemical limits on suitable drug candidates, and the main patch designs in use today. Strategies for improving permeation are discussed under three headings: chemical enhancers, physical methods (iontophoresis, sonophoresis, microneedles) and vesicular carriers. We also outline the standard evaluation tests for patches, list representative marketed products, and discuss the problems that still hold back wider use, including skin irritation, dose limits and manufacturing cost. Recent progress in microneedle technology suggests that large molecules such as peptides and vaccines may become feasible candidates in the coming years.

Keywords:

Transdermal patch; stratum corneum; skin permeation; penetration enhancers; microneedles; iontophoresis