Topical corticosteroids — Viva

Q1: Definition and classification (2 min)

What are topical corticosteroids? Classify them by potency and give one example for each tier. How does the vehicle affect the effective potency of the same molecule?

Q2: Pharmacology and body site absorption (3 min)

Explain the mechanism of action of topical corticosteroids. Why does the stratum corneum thickness matter for potency selection? Rank body sites from the highest to the lowest absorption.

Q3: Safe prescribing and dosing (2 min)

What is a fingertip unit? How much does it weigh, and how much body surface area does it cover? How many FTUs are needed for the face and neck, one arm, and one leg? What are the safe weekly limits for very potent topical corticosteroids in adults and children?

Q4: Clinical scenarios (3 min)

A patient with plaque psoriasis has thick plaques on the extensor elbows and knees. A patient with atopic dermatitis has facial involvement. Which potency and vehicle would you choose for each, and why? When would you use a steroid-sparing agent?

Q5: Adverse effects, complications, and counselling (2 min)

List the local and systemic adverse effects of topical corticosteroids. What is tinea incognito? What is tachyphylaxis, and how is it managed? How would you counsel a patient who is afraid of using topical corticosteroids?

Q6: Red flags and special populations (2 min)

What are the red flags that indicate topical corticosteroid use is dangerous or inappropriate? What special precautions apply in children, pregnancy, and the elderly?

Examiner notes

• Expected mentions: hydrocortisone 1% (mild), clobetasone 0.05% or betamethasone 0.025% (moderate), mometasone 0.1% or betamethasone 0.1% (potent), clobetasol propionate 0.05% (very potent).
• Must state that the face and flexures should receive only mild TCS; palms and soles can receive very potent agents.
• Must mention FTU as 0.5 g covering two adult palms (about 2% BSA).
• Must mention safe weekly limits of 50 g for very potent TCS in adults and 15 g in children.
• Must distinguish tinea incognito (masked, spreading fungal infection) from simple eczema and know the management (stop TCS, start antifungal).
• Must demonstrate ability to counsel on corticophobia and adherence.