Topical and Transdermal Drug Delivery

Abstract

This chapter reviews numerous concepts relevant to drug delivery topically and transdermally. Topics covered include the skin's function barrier, mechanisms for drug transport through the skin, in vitro analytical techniques, and methods to increase drug permeation. Commonly used formulation approaches such as semi-solid dosage forms and transdermal patches are also discussed. Keywords Topical drug delivery · Transdermal drug delivery · Percutaneous absorption · Fick's law of diffusion · Permeation enhancement · Semisolid dosage forms · Transdermal patches Learning Objectives • Compare and contrast topical and transdermal drug delivery. • Describe how the anatomy of the skin contributes to its barrier function. • Describe how Fick's law of diffusion can be applied to drug diffusion through the skin. • Discuss the factors affecting drug absorption across the skin. • Compare and contrast the routes of passive diffusion of drugs through the skin. • Describe how percutaneous absorption is assessed in vitro. • Explain the different approaches to enhance percutaneous absorption of drugs. • Discuss the types and uses of percutaneous absorption enhancers including chemical and physical methods used for transdermal products. • Explain the differences between an ointment, cream, and gel as dosage forms intended for topical application. • Explain the use and properties of transdermal patches to deliver drugs into the systemic circulation. • Understand what general clinical information the pharmacist should advise the patient when using transdermal drug delivery systems. Key Concepts Students should know and be able to describe each of the following concepts as they review this chapter: