Cyclosporin A does not inhibit epidermal cell growth at therapeutic levels.

The direct effect of cyclosporin A on epidermal cells was examined by using a pig skin explant culture system. A dose-response study using cyclosporin concentration from one-tenth the expected serum level to 100 times the expected serum level was done, and epidermal outgrowth and the number of mitotic figures were measured. Cyclosporin inhibited epidermal cell outgrowth at concentrations of 60 and 100 times the expected serum level, but it did not inhibit epidermal cell outgrowth at the serum level or even at 30 times the serum level. Cyclosporin did not inhibit mitotic figures significantly. These results suggest that cyclosporin does not inhibit epidermal cells directly.