[Application of synthetic retinoids and active vitamin D analogues to the skin disorders]

One of the synthetic retinoids Etretinate has been used in dermatology for the various inflammatory keratosis, congenital hyperkeratotic disorders and etc., and plays an important role in the treatment of these otherwise intractable skin diseases. But, it still has various side effects, the most serious among which being teratogenicity, and contraception for at least two years after cessation of the drug is recommended because of its very long half life. Acitretin, a nonesterified analogue with a much shorter half life and Isotretinoin are also used in the USA and Europe. The latter is reported to be very effective to severe cystic acne. Apparently, better compounds with less toxicity and a shorter half life are needed. A topical application of retinoid is under clinical evaluation. A topical application of active vitamin D3 and its analogues are shown to be effective for psoriasis, one of the most common intractable skin diseases. Calcitriol is already used in several European countries, and 1,24-dihydroxyvitamin D3 successfully completed aclinical studies in Japan. Topical vitamin D preparations will be important and useful in dermatology in the near future. Although an action of active vitamin D on the skin is not fully understood, we speculate that it plays an important role in the regulation of epidermal growth and differentiation.