Skin impedance and phoreographic index in psoriasis. Relationship with action kinetics of three treatments.

In a previous study, impedance measurements and phoreographic response were shown to quantify significant differences between involved and non-involved skin in psoriasis. The same techniques were used to objectivate the evolution on skin condition on patients treated with dioxyanthranol, difluprednate, and photochemotherapy associated with 8-methoxypsoralen. Each of these treatments was applied to four subjects. On patients treated with dioxyanthranol or difluprednate, impedance and phoreographic response return to "normal" values within 5--10 days and 1--2 days, respectively. It takes a longer time with photochemotherapy, and it is noteworthy that the treatment also alters the phoreographic response of non-involved skin. The changes observed in electrophysiological parameters are discussed in relation with recent ideas on pharmacology of antipsoriatic treatments and on dynamic properties of biological membranes. The results are in good correlation with clinical data and exemplify the usefulness of these methods in following the treatment kinetics.