Skin irritation by dithranol (anthralin) and its 10-acyl analogues in 3 animal models

The skin irritant properties of a single application of dithranol (anthralin), a typical "delayed irritant", and its 10-acyl analogues in acetone or white petrolatum were compared in 3 animals models. Maximal irritation was reached at about 24 h in mouse ear, 48 h in guinea pig back and 1 week in miniature swine back, the last-mentioned serving as a good model of human skin. In all animal species, butantrone was significantly less irritant than dithranol, 10-acetyl dithranol or 10-propionyl dithranol. 10-acetyl dithranol was the most irritant compound. Clinical trials with butantrone on psoriasis are justified.