DERMATOLOGICAL AGENTS

DERMATOLOGICAL AGENTS are used for a wide variety of purposes and some of the more important pharmacological types and terms will be discussed.

ANTIINFLAMMATORY AGENTS are frequently used to treat inflammatory and/or allergic reactions of the skin. The commonest agents used are CORTICOSTEROIDS (of the GLUCOCORTICOID type), which have potent antiinflammatory and ANTIALLERGIC properties. There is a range of steroids available as creams or ointments, which vary in concentration and the strength of the antiinflammatory action of the particular corticosteroid: the choice depends on the severity of the skin condition. Some preparations are available without prescription for minor skin inflammation, whereas at the other extreme some preparations are reserved for severe outbursts of eczema or psoriasis. There are many corticosteroids used clinically for dermatological conditions.

Inflammatory skin conditions are sometimes complicated by a coexisting infection, and there are many compound preparations available containing ANTIBACTERIAL or ANTIFUNGAL AGENTS together with an antiinflammatory corticosteroid.

ANTIPERSPIRANTS are substances that help to prevent sweating. Medically, they are needed only in cases of severe hyperhidrosis when some disorder of the sweat glands causes constant and streaming perspiration. In such cases, aluminium chloride solution is an effective treatment.

ASTRINGENTS precipitate proteins and are used in lotions to harden and protect skin where there are minor abrasions. They can also be used in lozenges, mouthwashes, eye-drops and antiperspirants. Examples include zinc oxide, and salts of aluminium (aluminium acetate, aluminium hydroxide).

Barrier creams are used to protect the skin against irritants, urine and toxic substances. They are normally applied as an ointment or cream and often incorporating a silicone (e.g. dimethicone).

Emollients/hydrating agents soothe and soften the skin. They are incorporated into ointments and skin creams that are used to treat conditions where the skin is dry or flaky (e.g. eczema). They are usually fats or oils, such as lanolin and liquid paraffin, and can be combined with other hydrating agents, e.g. urea.

Antipsoriatic agents are used to treat psoriasis, a serious chronic skin condition characterized by scaly pink patches. A number of agents may be used in treatment, but there is no cure. KERATOLYTIC (desquamating) agents are used extensively, including coal tar, dithranol, etretinate, ichthammol and salicylic acid; also retinoids (see below); and corticosteroids.

Retinoids (derivatives of retinol or vitamin A) are used to treat severe psoriasis resistant to other treatments, and certain other skin conditions (including severe Darier’s disease). They include acitretin, isotretinoin, which can be given by mouth, and tretinoin, which is used topically. Retinoids have a marked effect on differentiation of dermal cells of the epithelium of the skin.

Dithranol (an anthracene compound) is incorporated in a number of preparations, and is the most powerful drug presently used to treat chronic or milder forms of psoriasis in topical application. It is thought to work by inhibiting cell division (antimitotic) and may be used in combination with direct keratolytics.

Photosensitizers are agents that sensitize cells to radiation in the visible and near ultraviolet region of the radiation spectrum. Therapeutic use has been made of naturally occurring psoralens to treat vitiligo and psoriasis, in so-called photodynamic therapy. With newly developed UV irradiation systems that emit high-intensity UVA radiation, the principle has been extended to the treatment of severe psoriasis, mycosis fungoides and many other skin diseases. Agents used in psoralen photochemistry (PUVA) medicine include methoxypsoralen (8-MOP), trioxysalen and other synthetic psoralens.