Adrenocortical Steroids

Actions. Adrenal steroids possess a range of actions (see p. 664) of which the following are relevant to topical use:

• Inflammation is suppressed, particularly when there is an allergic factor, and immune responses are reduced

• Antimitotic activity suppresses proliferation of keratinocytes, fibroblasts and lymphocytes (useful in psoriasis, but also causes skin thinning)

• Vasoconstriction reduces ingress of inflammatory cells and humoral factors to the inflamed area; this action (blanching effect on human skin) has been used to measure the potency of individual topical corticosteroids (see below).

Penetration into the skin is governed by the factors outlined at the beginning of this chapter. The vehicle should be appropriate to the condition being treated: an ointment for dry, scaly conditions, a water-based cream for weeping eczema.

Uses. Adrenal steroids should be considered a symptomatic and sometimes curative, but not preventive, treatment. Ideally a potent steroid (see below) should be given only as a short course and reduced as soon as the response allows. Corticosteroids are most useful for eczematous disorders (atopic, discoid, contact) and other inflammatory conditions save those due to infection. Dilute corticosteroids are useful in psoriasis (see p. 309).

Adrenal steroids of highest potency are reserved for recalcitrant dermatoses, e.g. lichen simplex, lichen planus, nodular prurigo and discoid lupus erythematosus.

Topical corticosteroids are of no use for urticarial conditions and are contraindicated in infection, e.g. fungal, herpes, impetigo, scabies, because the infection will exacerbate and spread. Where appropriate, an adrenal steroid formulation may include an antimicrobial, e.g. miconazole, fusidic acid, in infected eczema.

Topical corticosteroids should be applied sparingly ('Marmite rather than marmalade'). The 'finger tip unit'5 is a useful guide in educating patients (see Table 16.1).

The difficulties and dangers of systemic adrenal steroid therapy are sufficient to restrict such use to serious conditions (such as pemphigus and generalised exfoliative dermatitis) not responsive to other forms of therapy.

• Use for symptom relief and never" prophylactically

• Choose the appropriate therapeutic potency (see Table 16.2). ¡.e. mild for the face. In cases likely to be resistant, use a very potent prepa ration, e.g. for

3 weeks, to gain control, after which change to a less potent preparation.

• Choose the appropriate vehicle, i.e. a water-based cream for weeping eczema, an ointment for dry scaly condition s.

• Use a combined adrenal steroid/antimicrobial formulation if infection is present.

• Advise the patient to apply the formulation very thinly, just enough to make the skin surface shine slightly.

• Prescribe in small but adequate amounts so that serious overuse is unlikely to occur without the doctor knowing, e.g. weekly quantity by group (Table I 6.2): very potent I 5 g; potent 30 g: others BO g.

• Occlusive dressing should be used only briefly. Note that babies' plastic pants are an occlusive dressing as well as being a social amenity

Choice. Corticosteroids are classified according to their therapeutic potency (efficacy), i.e. according to both drug and % concentration (see Table 16.2).

5The distance from the tip of the adult index finger to the first crease.

TABLE 16.1 Finger tip unit dosimetry for topical corticosteroids

Age

Face/ Arimf Leg/ Trunk Trunk Neck Hand Foot (front) (back, including buttocks)

3-6 months 1-2 years 3-5 years 6- 10 years Adult

Hand—1 Leg^6

TABLE 16.2 Topical corticosteroid formulations conventionally ranked according to therapeutic potency

TABLE 16.2 Topical corticosteroid formulations conventionally ranked according to therapeutic potency

Very potent Clobetasol (0.05%) [also formulations of diflucortolone {0.3%). halcinonide] Potent Beclo met has one (0.025%) [also formulations of betamethasone, budesonide. desonide. desoxymethasone, diflucortolone (0 1%), fluclorolone, fluocinolone (0.025%), fl uoc i no n ide. fluticasone, hydrocortisone buty rate, mometasone (once daily), triamcinolone]

Moderately potent Clobetasone (0.0S%) [also formulations of alclometasone. clobetasone, desoxymethasone. fluocinolone (0.00625%). fluocortolone, fluandrenolone. hydrocortisone plus urea (see p. 307)] Mildly potent Hydrocortisone (0 1-1.0%) [also formulations of alclomethasone, fluocinolone (0.0025%), methylprednisolone]

Important note: the ranking is based on agent and its concentration: the same drug appears in more than one rank.

Choice of preparation relates both to the disease and the site of intended use. High potency preparations are commonly needed for lichen planus and discoid lupus erythematosus; weaker preparations (hydrocortisone 0.5-2.5%) are usually adequate for eczema, use on the face and in childhood.

When a skin disorder requiring a corticosteroid is already infected, a preparation containing an antimicrobial is added, e.g. fusidic acid or clotrimazole. When the infection is eliminated the corticosteroid may be continued alone.

Intralesional injections are occasionally used to provide high local concentrations without systemic effects in chronic dermatoses, e.g. hypertrophic lichen planus and discoid lupus erythematosus.

Adverse effects. Used with restraint topical corticosteroids are effective and safe. Adverse effects are more likely with formulations ranked therapeutically as very potent or potent in Table 16.2.

• Short-term use. Infection may spread.

• Long-term use. Skin atrophy can occur within

4 weeks and may or may not be fully reversible. It reflects loss of connective tissue which also causes striae (irreversible) and generally occurs at sites where dermal penetration is high (face, groins, axillae).

Other effects include: local hirsutism; perioral dermatitis (especially in young women) responds to steroid withdrawal and may be mitigated by tetracycline by mouth for 4-6 weeks; depigmentation (local); acne (local). Potent corticosteroids should not be used on the face unless this is unavoidable. Systemic absorption can lead to all the adverse effects of systemic corticosteroid use. Fluticasone propionate and mometasone furoate are rapidly metabolised following cutaneous absorption which may reduce the risk of systemic toxicity. Suppression of the hypothalamic/pituitary axis readily occurs with overuse of the very potent agents, and when 20% of the body is under an occlusive dressing with mildly potent agents. Other complications of occlusive dressings include infections (bacterial, candidal) and even heat stroke when large areas are occluded. Antifungal cream containing hydrocortisone and used for vaginal candidiasis may contaminate the urine and misleadingly suggest Cushing's syndrome.6 Applications to the eyelids may get into the eye and cause glaucoma.

Rebound exacerbation of the disease can occur after abrupt cessation of therapy. This can lead the patient to reapply the steroid and so create a vicious cycle.

Allergy. Corticosteroids, particularly hydrocortisone and budesonide, or other ingredients in the for-

6 Kelly CI et al 2001 Raised Cortisol excretion rate in urine and contamination by topical steroids. British Medical Journal 322: 594.

mutation, may cause allergic contact dermatitis and the possibility of this should be considered where expected benefit fails to occur.

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