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Variability in human skin permeability in vitro: comparing penetrants with different physicochemical properties
Franklin K Akomeah1, Gary P Martin, Marc B Brown
1Pharmaceutical Sciences Research Division, Kings College London, Franklin-Wilkins Building, 150 Stamford Street, London, SE1 9NH, United Kingdom.
Journal of Pharmaceutical Sciences
|December 21, 2006
Summary
Understanding human skin variability is key for effective transdermal therapy. This study shows caffeine permeation varies more than parabens, impacting in vitro drug absorption studies.
Area of Science:
- Dermal and Transdermal Drug Delivery
- Pharmacokinetics and Drug Metabolism
- Biophysical Chemistry of Skin
Background:
- Percutaneous absorption variability necessitates careful consideration for optimizing transdermal drug delivery.
- Human skin exhibits inherent variability influencing drug penetration, impacting therapeutic efficacy.
Purpose of the Study:
- To investigate human skin permeability variability using model penetrants of varying lipophilicity: caffeine (CF), methyl paraben (MP), and butyl paraben (BP).
- To compare experimental permeability coefficients (K(P)) with predictions from Potts & Guy and Robinson (revised) models.
- To elucidate potential permeation pathways and validate the Franz diffusion method.
Main Methods:
- Standardized intra-laboratory study using Franz cell experiments with human epidermal tissue from multiple donors.
- Measurement of permeability coefficients (K(P)) for caffeine, methyl paraben, and butyl paraben.
- Comparison of experimental K(P) values with two established skin permeation models (Potts & Guy, Robinson revised).
Main Results:
- Intra-subject variability in skin permeation was generally lower than inter-subject variability.
- Experimental K(P) values were of the same order of magnitude as predicted by both models.
- Potts & Guy model accurately predicted paraben permeation; Robinson (revised) model was more effective for caffeine.
- Higher variability in caffeine permeation suggests increased sensitivity to skin lipid content, appendages, and imperfections for more hydrophilic solutes.
Conclusions:
- Variability in skin permeability, influenced by solute physicochemical properties, must be accounted for in in vitro drug permeation studies.
- Caffeine's permeation kinetics differ from parabens, highlighting the impact of lipophilicity on absorption variability.
- Mathematical models can predict skin permeability, but their accuracy varies depending on the solute's properties and the model used.
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