The effect of penetration enhancers on the kinetics of percutaneous absorption

Richard H. Guy, Jonathan Hadgraft

Research output: Contribution to journalArticlepeer-review


The effect of penetration enhancers on the kinetics of percutaneous absorption and transdermal drug delivery has been examined theoretically. Using a physically based pharmacokinetic description of skin absorption, the action of model promoters has been investigated as a function of the physicochemical properties of the penetrant. The kinetic simulation permits both zero- and first-order input of the drug from the delivery system; diffusion through the skin is modelled by consecutive transport steps across the stratum corneum and viable epidermis and by a partitioning process at the lipophilic-aqueous phase boundary between those two tissue layers. Two model enhancers, whose effects occur specifically in skin, are considered: the first (PE1) increases the drug diffusion coefficient (Ds) across the stratum corneum by an order of magnitude; the second (PE2) again increases Ds ten-fold but also reduces the effective stratum corneum-viable tissue partition coefficient of the drug to 10% of its unperturbed value. The action of these promoters is shown to be sensitive to the oil-water distribution characteristics of the drug: PE1 is effective for relatively hydrophilic compounds but becomes increasingly ineffectual as a drug lipophilicity increases (log K (moctanol/H2O)≥2); PE2, on the other hand, provides little additional effect over PE1 for hydrophilic substances but significantly enhances the transdermal delivery of hydrophobic moieties. It appears, therefore, that the desirable properties of a penetration enhancer may change depending upon the physico-chemical nature of the drug being delivered.

Original languageEnglish
Pages (from-to)43-51
Number of pages9
JournalJournal of Controlled Release
Issue number1
Publication statusPublished - 30 Jun 1987

ASJC Scopus subject areas

  • Pharmaceutical Science


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