[On interactions of drugs on and in the skin/comparative studies on the mutual influences of ethyleneglycol-monosalicylate and benzylnicotinate (author's transl)].

A Zesch, H Schaefer

Index: Derm. Beruf Umwelt. 29(6) , 161-7, (1981)

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Abstract

Three radioactively marked substances (on the basis of a carbopol gel, 80% water - isopropanol) were analyzed comparatively in regard to the penetration of ethyleneglycolmonosalicylate and benzylnicotinate to intact and impaired human skin. The objective of the in-vitro study was to gain evidence on possible interaction of the locally applied substances upon skin penetration. Only 5 h after application ethyleneglycolmonosalicylate reaches a steady state of concentration in the corium of approximately 700-800 mumol/l tissue which is maintained (in contrast to nicotinate) even after 16 h exposure time. Benzylnicotinate reaches its maximum concentration (100-200 mumol/l tissue in all living layers of the skin) 100-300 min after application. After simultaneous local application of both substances the penetration of ethyleneglycolmonosalicylate in corium and subcutis is clearly intensified by benzylnicotinate. Substance distribution in skin cross section and kinetics do not change. Penetration of benzylnicotinate however, is delayed by the salicylate (especially at exposure time of 100-300 min). Results of comparative penetration studies with inverted skin (inverse penetration), intact and impaired (stripped) skin allow the following conclusion: penetration limiting of salicylate occurs in the horny layer only due to the optimal liberation. Penetration of nicotinate on the other hand, is already prevented "before" the skin because of insufficient liberation from the vehicle.