PH9.6 | PH9.6 | Dermatological Pharmacotherapy — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Acne: Step-up treatment — topical: benzoyl peroxide (P. acnes-cidal, does NOT promote resistance) + retinoid (tretinoin/adapalene — normalises keratinisation) ± topical clindamycin; oral: doxycycline for moderate; isotretinoin (13-cis-retinoic acid — reduces sebum 90%, induces remission; Pregnancy Category X — pregnancy test + 2 contraceptives mandatory); hormonal OCP with cyproterone for females. Scabies: Permethrin 5% cream (overnight, from neck down, repeat week 1) — first-line; benzyl benzoate 25% second-line; ivermectin oral for crusted/resistant. Treat all household contacts simultaneously. Pediculosis: Permethrin 1% (10 min leave-in, repeat 7–10 days); malathion 0.5% second-line. Psoriasis — topical: corticosteroids (anti-inflammatory, risk atrophy/tachyphylaxis); calcipotriol (VD3 analogue, normalises keratinocyte differentiation, no atrophy); coal tar; dithranol. Systemic: methotrexate 7.5–25 mg ONCE WEEKLY (NEVER daily — fatal) + folic acid; ciclosporin; acitretin (teratogenic); biologics (anti-IL-17, anti-IL-23, anti-TNF for moderate-severe). Sunscreens: SPF = UVB protection only; 'broad spectrum' = UVA+UVB; physical blockers (zinc oxide, titanium dioxide) — photostable, preferred for sensitive skin/infants.

REFLECT

Consider the patient who comes to you asking for isotretinoin for their severe acne. They have done extensive online research and are aware of reports linking isotretinoin to depression and suicidal ideation. How do you navigate a nuanced evidence-based discussion about this risk (the evidence is contested and the baseline rate of depression in acne patients is high) while also conveying the mandatory teratogenicity monitoring requirements? What does this case teach you about the intersection of pharmacology, patient autonomy, and prescriber responsibility? Separately, reflect on the methotrexate weekly dosing issue — what system-level safeguards (in hospital dispensing, prescribing software, patient education) would you advocate for to prevent this well-documented, fatal prescribing error?