Vitamin D analogues in the treatment of psoriasis

Psoriasis is a chronic hyperproliferative skin disease in which inflammatory and immunologic processes may play important pathophysiologic roles. Recently the skin has been identified as a target tissue for vitamin D. Because 1,25‐dihydroxy vitamin D 3 inhibits epidermal proliferation and promotes epidermal differentiation, it has been introduced for the treatment of psoriasis vulgaris. In addition to 1,25‐(OH) 2 ‐D 3 , synthetic vitamin D 3 analogues have undergone clinical evaluation. Calcipotriol (INN) (calcipotriene [USAN]) has been studied most extensively. Compared with 1,25‐(OH) 2 ‐D 3 , calcipotriol is about 200 times less potent in its effects on calcium metabolism, although similar in receptor affinity. Topical calcipotriol 50 μg/g applied twice daily is efficacious and safe for the treatment of psoriasis. Because topical calcipotriol is slightly more efficacious than betamethasone 17‐valerate and dithranol, calcipotriol should be considered a first line drug in the management of psoriasis. These results illustrate that it is possible to separate the vitamin D effects on the cellular level from those on calcium metabolism not only in vitro, but also in a clinical setting.