Topical forms of vitamin S (retinoids) have been used widewly in the USA for many years. The first retinoid to be used topically was all-trans retinoic acid developed by Dr. Albert Kingmnan. It was brought to market in the 1970s . Vitamin A is required for normal growth of many tissues. Excessive quantities can adversely affect the embyro and fetus in pregnancy

The topical retinoid drug mechanisms


 All trans retinol     Gene transcription comedolysis, epidermal thickening, dermal regeneration, pigment lightening Irritation, red skin, skin peeling

 All trans retinoic acid Gene transcription Comedolysis, palliative effects on fine wrinkling and reducing mottled hyperpigmentation and tactile roughness of facial skin,  Irritation, red skin, skin peeling

 Adapalene normalizes differentiation of epithelial cells Comedolysis Irritation, red skin, skin peeling, skin burning, itching

 Tazarotene Blocks induction of ornithine decarboxylase activity Normalizes differentiation and proliferation of the epidermalkeratinocytes in psoriasis, also comedolysis in acne Irritation, red skin, skin peeling, skin burning, itching, photosensitvity, dry skin, fissuring, bleeding, teratogenic

 Alitretinoin Activates RXR and RAR receptors Inhibits growth of Kaposi's sarcoma cells in vitro Irritant contact dermatitis, redness, scaling, itching, teratogenic

 Bexarotene modulation of RXR receptors  Central Hypothyroidism, redness, irritation to skin, itching, teratogenic