Dermatology, retinoids

Vitamin A constitutes the most significant sector of the commercial retinoid market and is used primarily in the feed area. In the pharmaceutical area, there are several important therapeutic dermatologic agents which stmcturaHy resemble vitamin A and they are depicted in Figure 2 (see Pharmaceuticals). The carotenoids as provitamin A compounds also represent an important commercial class of compounds with P-carotene [7235-40-7] (10) occupying the central role (Fig. 3) (9). 

Future generations of such receptor subtype-selective retinoids or also retinobenzoic acids [3] may provide clinicians with more specific and less toxic diugs for dermatologic therapy. 

Retinoids. Table 1 Indications and mode of administration of commercially available retinoids in dermatological therapy... 

ShalitaAR, Fritsch PO (eds) (1992) Retinoids Present and Future. Proceedings of a Symposium Held at the 18th World Congress of Dermatology Supplement to J Am Acad Dermatol 27 part 2... 

There are many retinol containing preparations to treat vitamin deficiency states. Retinoids are also used to treat dermatological diseases like acne, psoriasis, Darier s disease, and ichthyosis. Tretinoin, all-trans-retinoic acid, is a topical preparation while isotretinoin or 13-cis-retinoic acid, and etretinate are available for oral administration. 

Retinoids are a family of naturally occurring and synthetic analogues of vitamin A. The skin of subjects deficient in vitamin A becomes hyperplastic and keratotic (phrynoderma, or toad skin). While natural vitamin A is occasionally employed therapeutically, synthetic retinoids are more effective and represent a major advance in dermatological pharmacotherapy. Retinoids have myriad effects on cellular differentiation and proliferation it is likely that nuclear retinoic acid receptors mediate these effects by activating gene expression in a manner analogous to receptors for steroid hormones and thyroid hormones. Despite a common mechanism of action, however, retinoids vary widely in their physiological effects. 

Vitamin A and its retinoid analogues have gained popularity in the treatment of acne and other dermatological diseases (see Chapter 41). 

Retinoid acid is a transcription factor. Retinoids play significant roles in dermatology, in the prevention of some cancers, and in the chemistry of vision. Consequently, many works have been dedicated to fluorinated analogues of retinoids. 

Dermatological reactions to lithium include acne, follicular eruptions, and psoriasis. Hair loss and thinning also have been reported. Except for cases of exacerbation of psoriasis, these reactions are usually benign and may not warrant discontinuation of lithium treatment. Lithium-induced acne responds to topical treatment with retinoid acid, such as tretinoin (Retin-A). 

The UV radiation causes premature skin aging. This photo-aging is characterized by wrinkles, mottled pigmentation, dry and rough skin, and loss of skin tone. Use of topical vitamin A derivatives like tretinoin can improve photo-aged skin mainly by changing epidermal differentiation.52 However, skin dryness does not improve and even worsens with retinoid therapy, as well known from its systemic and topical use in several diseases in clinical dermatology. 

For dermatological treatment the main focus has been on vitamins A and D. Retinoids have been used systemically and topically for the treatment of acne and a variety of hyperkeratotic disorders including psoriasis, ichthyoses, and lichenoid dermatoses as well as skin cancer.1 Vitamin D-analogs are of great importance for the topical treatment in psoriasis. 

Zouboulis, C.C., Retinoids — which dermatological indications will benefit in the near future Skin Pharmacol. Appl. Skin Physiol., 14, 303, 2001. 

Retinoids in Dermatology 13-Qs-retinoic acid (isotretinoin, Accutane ) is used orally, and all-trans-retinoic acid (Tretinoin ) topically, for treatment of severely disfiguring cystic acne. Etretinate (the trimethoxyphenyl analog of retinoic acid) and tazarotene (a receptor-specific retinoid) are used topically for the treatment of psoriasis. They are effective in cases in which other therapy has failed, and at lower levels than are required for the control of tumor development in experimental animals, although they have heen associated with hirth defects (Section 2.5.1.1 fohnson and Chandrarama, 1999). 

Johnson A and Chandraratna RA (1999) Novel retinoids with receptor selectivity and functional selectivity. British Journal of Dermatology 140(Suppl 54), 12-17. 

Sass JO, Jakob-Solder B, Heitger A, Tzimas G, Sarcletti M. Paronychia with pyogenic granuloma in a child treated with indinavir the retinoid-mediated side effect theory revisited. Dermatology 2000 200(l) 40-2. 

Nyirady J, Grossman RM, Highland M, Berger RS, Jorizzo JL, Kim YH, Martin AG, Pandya AG, Schulz KK, Strauss JS. A comparative trial of two retinoids commonly used in the treatment of acne vulgaris. J Dermatolog Treat 2001 12(3) 149-57. 

---