Transcutaneous drug delivery: a practical review

To describe the advantages, disadvantages, practical considerations, and future developments of transcutaneous drug delivery.

The physiochemical properties of the drug preparation that are factors in the effectiveness of transcutaneous transport are drug stability or volatility, use of a solvent carrier or vehicle, use of a penetration enhancer, and type of delivery device. Because a drug should remain on the skin without evaporating or becoming otherwise inactive, it is suspended in a vehicle--any gel, lotion, or paste used to apply the drug to the skin. Penetration enhancers include several compounds that are mixed into vehicles to alter the molecular environment of the epidermis and facilitate absorption. The delivery system itself occasionally proves to be the ultimate determinant of transdermal drug flow.

The advantages of transcutaneous drug delivery are avoidance of the gastrointestinal tract and hepatic first-pass biotransformation and metabolism, control of absorption, availability of multiple skin sites to avoid local irritation and toxicity, and improved patient compliance. The disadvantages include the potential for localized irritant and allergic cutaneous reactions, systemic toxicity, and difficulties associated with the time necessary for a drug to diffuse through the skin.

Transdermal drug regimens are safe and effective. They provide clinicians the opportunity to offer more therapeutic options to their patients to optimize their care.