Retinoic acid is a class of natural or synthetic derivatives of vitamin A. Vitamin A is necessary for normal epithelial proliferation and differentiation. But in the treatment of skin diseases, it has adverse reactions. Its molecular structure‘s improvement provides a variety of compounds with similar structures. They are collectively referred as tretinoin. Because it can not treat vitamin A deficiency, so it does not actually belong to the scope of the vitamins.

Retinoids were first started in 1962 and used in dermatology, has been a 40-year history. Represents the advent of a milestone in modern dermatology therapy for refractory skin disease provide new and effective therapeutic approach, known as the nearly half a century used in dermatology treatment in the three most important One of the findings (the other two penicillin and glucocorticoid hormones. It has been gradually used in local and systemic treatment of psoriasis, hyperkeratosis and parakeratosis skin the keratinizing genetic skin diseases, severe acne and acne-related skin diseases, but also treatment and prevention of skin aging and tumor formation; has become the treatment of psoriasis, ichthyosis and acne drugs indispensable.

The synthesis of retinoic acid compounds has been more than 1500 kinds. Its structure consists of three parts, namely, the ring structure of the polyene side chain and the polarity of the terminal groups. The transformation of the part can get a series of retinoic acid derivatives. However, in clinical practice less than ten kinds of practical value. Retinoids traditionally divided into three generations, first on behalf of non-aromatic, the earliest applications of all-trans retinoic acid, oral side effects, are now outside the main application of the most different
minoxidil and viaminate. Second generation single aromatic retinoic acid: acitretin ester and its major metabolite Avi A third behalf of multi-aromatic Retinoids aromatic retinoic acid ethyl ester and receptor selectivity, The three topical application of the retinoids adapalene, acetylene retinoid tazarotene and shellfish accounted for Lines of Flight, respectively, to treat acne, psoriasis and cutaneous lymphoma.

For comprehensive and objective assessment of a variety of retinoic acid, researchers have put forward the concept of retinoic acid treatment index. It refers to fasting minimum daily dose of vitamin polycythemia and cause 50% papilloma regression with retinoic acid amount. It mainly reflects the relationship between drug efficacy and adverse effects. Short-term treatment of retinoic can produces side effects on the skin, liver, blood lipids, and teratogenicity acid. And long-term use accumulation’s side effects are bone and ligament calcification, such as causing diffuse idiopathic bone hypertrophy, etc.Source: