SIMULTANEOUS ABSORPTION OF COPPER AND ZINC THROUGH HUMAN SKIN IN-VITRO - INFLUENCE OF COUNTERION AND VEHICLE

Copper and zinc percutaneous absorptions were assessed in vitro using sliced human skin and both petrolatum and hydrophilic gels as vehicles . Applied quantities were largely in excess for the duration of the ex periment (72 h). The absorption of sulphates and chlorides was compare d. The cumulated amount recovered in receptor fluid was below 50 mu g/ cm(2). The apparent permeability constant values kept in the range of 10(-6) cm h(-1), except for ZnCl2 in gel vehicle(2.9 10(-5) cm h(-1)). With the exception of CuCl2 in gel vehicle, chlorides gave higher abs orption rates than sulphates. This can be related to the higher octano l-water partition coefficient of chlorides. Storage within the epiderm is was found to be equal to or greater than, and within the dermis equ al to or lower than the 72-hour cumulative amount in receptor fluid. N o difference was found in this respect between copper and zinc. This w ork confirms the poor absorption of electrolytes through normal human skin, whatever the vehicle used.