[Relation of the vehicle to urea penetration in human skin]

Prerequisite to any efficiency of urea in the skin is its penetration into the different skin layers. In addition to the differences in the reactivity of the skin, the ointment base is the most important factor for the intensity and the course of urea penetration. For the penetration of urea into the human skin a strong vehicle dependence can be proved. On the basis of a different penetration kinetics of urea from O/W and W/O emulsions, various efficiencies can be deduced with regard to the penetration promotion of drugs or the increase of the water-binding capacity of the horny layer. The significance of these findings for the use of urea in the external therapy is being discussed.