Spironolactone Acne — SCE Dermatology MCQ

Correct answer: A — Spironolactone is an aldosterone antagonist that also blocks androgen receptors and inhibits 5-alpha reductase, reducing sebum production

Option A is correct: spironolactone is an aldosterone antagonist that also blocks androgen receptors and inhibits 5-alpha reductase, reducing sebum production. In hormonal acne, excess androgen action on the pilosebaceous unit drives sebum overproduction and comedone formation. Spironolactone competitively blocks androgen receptors in the sebaceous gland and reduces peripheral conversion of testosterone to the more potent dihydrotestosterone via 5-alpha reductase inhibition, directly targeting this pathway. This is why UK guidance supports its off-label use in adult women with persistent, treatment-resistant or hormonally-patterned acne (jawline and chin distribution, premenstrual flares), particularly when combined oral contraceptives are contraindicated or ineffective. Its anti-mineralocorticoid action explains why potassium and blood pressure monitoring are advised, but this is a separate effect from its anti-acne mechanism. Why the other options are wrong: B. It blocks IL-17: IL-17 blockade is the mechanism of biologics such as secukinumab used in psoriasis and psoriatic arthritis, not a mechanism relevant to acne or to spironolactone. D. It is a PDE4 inhibitor: PDE4 inhibition describes drugs like roflumilast (used in COPD) or topical roflumilast/crisaborole in dermatitis; spironolactone has no phosphodiesterase activity. E. It is a retinoid: Retinoids (topical tretinoin, oral isotretinoin) act via retinoic acid receptors to normalise keratinisation and reduce sebocyte proliferation, an entirely different mechanism from spironolactone's hormonal action. C. It kills bacteria: Antibacterial activity against Cutibacterium acnes is the mechanism of agents such as topical benzoyl peroxide or oral tetracyclines; spironolactone has no antimicrobial effect. Key point: Spironolactone treats hormonal acne through anti-androgenic effects (receptor blockade plus 5-alpha reductase inhibition) rather than through any antibacterial, retinoid, or cytokine-blocking mechanism.

Reference: NHS Right Decisions (Scotland), 'Spironolactone for Persistent Acne in Women in Primary Care', reviewed guidance referencing NICE CKS Acne Vulgaris: Management (2021), https://www.rightdecisions.scot.nhs.uk/media/i34bto3p/1206-spironolactone-acne-women-v1-jl.pdf