Role of partition coefficients in determining the percutaneous penetration of salicylic acid and formaldehyde under varying occlusion durations |
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Authors: | Farhaan Hafeez Audris Chiang Xiaoying Hui Howard Maibach |
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Affiliation: | Dermatology Department, University of CaliforniaSan Francisco, CAUSA |
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Abstract: | Context: Occlusion is widely utilized to enhance the percutaneous penetration of applied drugs in clinical practice; however, occlusion does not increase the penetration of all chemicals.Objective: This study determines: (1) whether occlusion enhances the percutaneous penetration of the lipophilic salicylic acid or the hydrophilic formaldehyde when compared to non-occlusion, (2) evaluate whether occlusion duration affects the penetration of compounds and (3) establish to what extent occlusive films in clinical practice interact with topically-applied chemicals and possibly hinder penetration.Materials and methods: Separately, single doses of [14C]-formaldehyde and [14C]-salicylic acid were applied onto human skin overlying diffusion cells under non-occlusion as well as various occlusive time periods (1, 4 and 8?h). The percent dose penetrating into each compartment as well the percent dose adhering to the plastic wrap were determined.Results: The radioactivity recovery as percent of applied dose of [14C]-salicylic acid was significantly higher under occlusion versus non-occlusion in the epidermis, dermis and receptor fluid after 24?h (p?0.05). For [14C]-formaldehyde, no significant statistical differences were observed between occlusion versus non-occlusion. The plastic wrap often used to enhance the penetration of topically applied drugs does not itself substantially adhere to the tested chemicals.Conclusion: Occlusion duration, previously undocumented for in vitro studies, impacted the percutaneous penetration of the lipophilic salicylic acid more so than the hydrophilic formaldehyde. A strong correlation between occlusion-enhanced penetration and partition coefficients was observed, but we do not wish to overgeneralize these results until more compounds of varying physical--chemical properties are studied. |
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Keywords: | Barrier function in vitro occlusion partition coefficient percutaneous penetration stratum corneum |
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