Topical Corticosteroids

Topical corticosteroids are the most used anti-inflammatory drugs in dermatology and are first-line therapy for eczema, psoriasis plaques, lichen planus, lichen sclerosus, discoid lupus and many other inflammatory dermatoses. They are graded by potency from mild to very potent. Efficacy, atrophy risk and systemic absorption all rise with potency, so choice of potency, vehicle, site and duration decides outcome.

Mechanism. Binding to the intracellular glucocorticoid receptor changes gene transcription: reduced production of inflammatory cytokines and prostaglandins, inhibition of T-cell and antigen-presenting cell function, antiproliferative effect on keratinocytes and fibroblasts, and vasoconstriction (the basis of blanching potency assays).

Pharmacokinetics. Absorption through the stratum corneum varies with site (forearm 1, scalp about 3.5, forehead and flexures about 6 or more, scrotum over 40), skin barrier damage, occlusion (up to tenfold increase), hydration and vehicle (ointment more than cream more than lotion). Infants and older adults absorb more relative to body weight. Metabolism is hepatic after systemic absorption.

Mometasone and fluticasone have a favourable ratio of anti-inflammatory effect to atrophy. Ointments are preferred for dry, thick, lichenified skin; creams for weeping or intertriginous skin; lotions, foams and gels for the scalp and hairy areas.

Use principles.

• Apply once daily in most conditions; twice daily is seldom more effective. Dose by fingertip unit (about 0.5 g covers an area equal to two adult palms).
• Start with the lowest potency likely to work, escalate for a short period, then step down. Use mild to moderate potency on the face, flexures and genitalia; potent to very potent on palms, soles and lichenified plaques.
• Duration: very potent for no more than 2 to 4 weeks at a time (maximum about 50 g weekly in adults); potent for up to 4 to 8 weeks; mild on the face for no more than 1 to 2 weeks without review. Use weekend or twice-weekly maintenance for relapsing atopic eczema and psoriasis.
• Lichen sclerosus (genital): clobetasol 0.05 percent ointment daily for 4 to 12 weeks, then 2 to 3 times weekly as maintenance.
• Alopecia areata: intralesional triamcinolone 2.5 to 10 mg/mL, repeated every 4 to 6 weeks.
• Children: milder preparations, shortest course; avoid potent steroids under occlusion in the nappy area.

Selection. Stop or avoid in untreated skin infection, rosacea, perioral dermatitis, acne, leg ulcers and undiagnosed rashes.

Local effects. Skin atrophy, striae (permanent), telangiectasia, purpura, delayed healing, steroid-induced acne and periorificial dermatitis, rosacea flare, hypertrichosis, hypopigmentation, tinea incognito, contact allergy to the steroid or vehicle, and glaucoma and cataract with periocular use.

Systemic effects. HPA axis suppression, growth retardation and Cushing syndrome with prolonged use of potent or very potent agents over large areas, under occlusion, or in infants. Rebound or pustular psoriasis after abrupt withdrawal; topical steroid withdrawal syndrome (burning erythema after long facial use).

Interactions. Systemic exposure can interact with CYP3A4 inhibitors (ritonavir, itraconazole), raising steroid levels.

Monitoring. Review skin at 2 to 4 weeks; measure growth in children on prolonged therapy; check morning cortisol if adrenal suppression is suspected.

Special groups. Pregnancy: mild to moderate steroids are preferred; large amounts of very potent steroids are associated with low birth weight. Breastfeeding: avoid application to the nipple before feeding. Older adults: skin atrophy and bruising occur sooner.

Region: skin lightening creams containing clobetasol and other potent steroids (often with hydroquinone or mercury) are widely sold in East Africa and cause atrophy, striae, acne, adrenal suppression and delayed wound healing; steroid-containing creams sold for fungal infection cause tinea incognito. Ask about every cosmetic product used.