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( Richard H Guy ) 한국피부장벽학회 2013 한국피부장벽학회지 Vol.15 No.2
The delivery of drugs into and through the skin either for dermatological therapy, or to treat local, subcutaneous inflammation, is challenging. The reliable prediction of a drug`s permeability through the skin is a topic of continuing interest. Just as Lipinski`s rules-of-5 have introduced physicochemical criteria for oral drug candidates to satisfy (in addition to being selectively active at a specific pharmacological target), similar feasibility properties must also be applied to the topical/transdermal route of administration. For dermatological medicines, the fraction of the drug placed on the skin surface that penetrates to the site of action is typically very small. To improve this situation suitable methodologies with which to quantify drug delivery to specific locations within the skin are required. Novel imaging technology, such as Raman scattering microscopy, is providing insight into the ‘metamorphosis’ of topical drug formulations post- application and mechanistic information about local drug disposition on and within the barrier. Finally, considerable attention currently focuses on the optimisation of topical delivery systems, and a variety of strategies have evolved to improve and enhance the rate and extent to which drugs reach their targets within the skin. As always, overcoming the stratum corneum`s impressive barrier function requires innovation and insight.
Effect of Enhancers on the Electrical Properties of Skin : The Effect of Azone and Ethanol
Oh,Seaung Youl,Richard H. Guy 한국약제학회 1994 Journal of Pharmaceutical Investigation Vol.24 No.3
The effect of Azone and ethanol on the electrical properties of human and hairless mouse skin was studied and the results were compared. The complex electrical impedance was measured as a function of frequency, and resistance and capacitance were determined from Nyquist plot. After the treatment of human-heat separated epidermis with Azone, contrary to the expectation, resistance increased about 60% and it did not change with time. Capacitance also increased; immediately after the treatment, it was about 110% of pretreatment value and it increased further with time. On the other hand, when hairless mouse skin was treated with Azone, marked changes occurred; resistance fell almost to the value of bathing medium itself and capacitance increased to about 200% of its pretreatment value. Similar result were obtained when hairless mouse skin was treated with 100% ethanol. The results suggest that there are differences in the strength of barrier properties of stratum corneum (SC) between human and hairless mouse skin. Overall, the results provide further mechanistic insight into ion conduction through the skin and into the role of SC lipids in skin capacitance.
The Effect of Oleic Acid and Propylene Glycol on the Electrical Properties of Skin
오승열,Oh, Seaung-Youl,Guy, Richard H. 한국약제학회 1994 Journal of Pharmaceutical Investigation Vol.24 No.4
The effects of oleic acid, propylene glycol and 5% (w/w) oleic acid in propylene glycol on the electrical properties of hairless mouse skin were studied and the results were compared. The complex electrical impedance was measured as a function of frequency, and resistance and capacitance were determined from the Nyquist plot. Immediately after the treatment with oleic acid, resistance was 145% of the pretreatment value. However it decreased with time and, after 20 hours, it was about 25% of its pretreatment value. Capacitance increased; immediately after the treatment, it was about 125% of pretreatment value and it seemed to increase slowly with time. When the skin was treated with propylene glycol, resistance decreased about 5O% and capacitance increased about 65%. Similar results were observed when the skin was treated with 5% (w/w) oleic acid in propylene glycol, except that the magnitude of resistance drop was much larger. Oleic acid acted synergistically with propylene glycol. Together with the flux data in the literature, the results obtained in this work indicate that electrical resistance is closely related to the permeability of drug molecules through the skin. The results are discussed in terms of the mechanism of action of these penetration enhancers. Overall, this work provided further mechanistic insight into the role of SC lipids in skin resistance and capacitance.