ABSTRACT
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Among the myriad strategies employed to increase both the amount of a therapeutic agent
traversing the skin and the range of drugs that can be effectively delivered through this route,
lies in the application of chemical penetration enhancers. These agents interact with stratum
corneum constituents to promote drug flux. Such materials have been used empirically in
topical and transdermal preparations for as long as pastes, poultices, creams, and ointments
have been applied to skin, though it is only over the last four decades that enhancers have
been employed deliberately for this specific purpose. To date, nearly 400 chemicals have been
evaluated as penetration enhancers (accelerants, absorption promoters), yet their inclusion
into topical or transdermal formulations is limited because the underlying mechanisms of
action of these agents are seldom clearly defined and regulatory approval is costly and
difficult. Here, we review some applications of the more widely investigated chemical pene-
tration enhancers and consider some of the complex mechanisms by which they may exert
their activities.
