Urea and derivatives as penetration enhancers

Abstract

Urea has long been used in topical and transdermal preparations and is variously described for its moisturising, keratolytic and penetration-enhancing activities. This chapter describes the historical use of urea in dermal products, describes the use of urea as an emollient in managing skin disorders such as atopic dermatitis and considers the literature reports of urea as a permeation enhancer. In attempts to increase the penetration enhancement activity of the molecule, several studies have reported chemical modifications of urea and the consequent accelerant activities towards permeants. Finally, considering the keratolytic properties of urea and, in several products, its long-term use, the chapter closes with a discussion of the safety of the molecule and its regulatory status.