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TOPICAL STEROIDS

Topical corticosteroids are widely used in dermatology for their antiinflammatory properties. They are usually applied b.i.d. initially and then can be tapered to once daily or as needed. Some are designed for once-daily use.

    Potency varies greatly and is mainly a function of the steroid molecule rather than of the concentration. For example, clobetasol propionate 0.05% is ultrahigh potency, whereas hydrocortisone 1% is of low potency. The grading systems for potency vary between countries, for example a class 1 steroid in the USA is superpotent, whereas the UK system uses four grades from ‘mild' to ‘very potent', starting with the lower potency. Also, availability of some agents differs worldwide. To avoid confusion, we have not listed agents and potencies here but refer readers to larger or more specific texts, or to prescribing formularies pertinent to their country of work.

    Vehicle influences potency as well, with ointments being ‘stronger' than creams, which are in turn ‘stronger' than lotions or solutions. Lotions and solutions have the problem of evaporation, which can leave inert steroid crystals that are unable to penetrate—a particular problem on scaly scalp psoriasis, for example, as discussed in the treatment section of Chapter 7. Some manufacturers make ready-diluted versions of topical steroids (typically 1:4); these are not inherently milder, although they may mean that less is used.

    The choice of strength of steroid usually depends on the disease being treated and the body location (Figs 3.2–3.5). For examples, see Table 3.1. The general approach, which can be learned only by experience, is to choose a steroid of adequate potency to control the disease, and then to reduce potency and/or frequency. Overcautious creeping up the potency ladder means the patient has symptoms for longer (a problem in some patients or their parents who have steroid phobia), while an excessively strong agent exposes the patient to the risk of side effects if it is overused.

    An appropriate amount to prescribe, for adults having b.i.d. application of a topical steroid, is discussed in some detail earlier but can be summarized as follows (bearing in mind that many topical steroids and other agents are packaged in tubes containing 30g or 100g, as reflected in the recommendations below).

•  Face and neck, or scalp: 15–30 g/week.

•  Both hands (palm and dorsum): 15–30 g/week.

•  Both arms: 30–60 g/week.

•  Both legs: 100 g/week.

•  Trunk, front, and back: 100 g/week.

Remember that quantities of creams or ointments required for use as an emollient are greater, as discussed earlier.

    To help patients to apply the correct amount of topical steroid, a commonly used measure is the fingertip unit. Because of the uniform nozzle size of most tubes, the weight of a strip of cream or ointment squeezed from a tube and extending from the tip of the finger to the crease at the distal interphalangeal joint in an adult is 0.5 g.

Figure. 3.2 Psoriasis of the hands. Psoriasis requires a high-potency steroid, as do the palms. Together, they require a superpotent topical steroid.

Fig. 3.3 Seborrheic dermatitis of the axilla. Seborrheic dermatitis requires only a low- to medium-potency steroid. The axilla provides its own occlusion. Thus a low-potency topical steroid would be appropriate.

Figure. 3.4 Nummular eczema. Unlike most of the other eczemas, nummular eczema requires a high-potency topical steroid.

Figure. 3.5 Eczema on the face of a child. A low-strength topical steroid is indicated because of the age, facial location, and eczematous process.

Table 3.1 EXAMPLES OF DISEASES AND BODY SITES THAT
DETERMINE THE REQUIRED STEROID POTENCY

Steroid potency	Disease	Body site(s)
High	Psoriasis (depends on site) Nummular eczema Lichen planus (most sites)	Palms and soles Heavily lichenified skin
Medium	Atopis dermatitis (depends on site)	Trunck and Legs
Low	Seborrheic dermatitis Mild eczema	Face Intertriginous areas

    Less frequently used methods for topical or local steroid use include:

•  steroid-impregnated tape (e.g. for keloid scars, to confine the steroid to the application site),

•  intralesional steroid injections (e.g. for keloid scars and nodular prurigo), and

•  steroid mouthwash (e.g. betamethasone tablets dissolved in water for oral lichen planus).

SIDE EFFECTS

The use of topical steroids can lead to many side effects, including skin thinning (atrophy; Fig.3.6), striae, purpura, folliculitis (particularly when ointments are used), steroid rosacea, and, on the face, perioral dermatitis (Table 3.2). Allergic contact dermatitis may occur as well. Systemic absorption can occur, and suppression of plasma cortisol may result in patients using a potent steroid over a large BSA (some modern steroids are metabolized in the skin and should avoid this problem, e.g. fluticasone and mometasone).

    Tachyphylaxis is not a side effect, but describes the situation in which the effectiveness of an agent decreases after several weeks of use. Its occurrence can be minimized by patients taking a periodic drug holiday.

PRACTICE POINTS

•  Tazarotene is the most efficacious of the topical retinoids for acne.

Figure. 3.6 Steroid atrophy. Topical steroids over 6 months caused these changes of striae and ulceration. Stopping all steroids is indicated!

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.