3rd Year MBBS
MSK
Topic 19 — Pharmacotherapy of Inflammatory, Pruritic, Pigmentary and Appendageal Skin Disorders
Connect the major drug targets, therapeutic effects and important cautions for rapid KMU-focused revision.
1. THE TOPIC IN ONE CONNECTED FLOW
Dermatological pharmacotherapy becomes easier when each drug is linked to the process it modifies. Acne treatment targets follicular obstruction, bacteria, sebum and inflammation; immunomodulators alter local immune activity; ectoparasiticides kill mites or lice; and drugs used in pigmentation, psoriasis, pruritus and hair disorders act on specific cellular or biochemical targets.
2. KEY CLINICAL CONNECTIONS
Follicular hyperkeratinization → topical retinoids normalize keratinization → fewer comedones.
C. acnes + inflammation → benzoyl peroxide or antibiotics → reduced bacterial load and inflammatory lesions.
Imiquimod → TLR7 activation → increased cytokine-mediated local immunity → useful for warts and selected superficial neoplastic lesions.
Tacrolimus → calcineurin inhibition → reduced T-cell cytokines → improved atopic dermatitis without characteristic steroid-induced skin atrophy.
Keratinocyte hyperproliferation → calcipotriol, retinoids or keratolytic support → thinner, less scaly plaques.
Immune inflammation → corticosteroids, methotrexate, cyclosporine or biologics → reduced inflammatory activity, with toxicity depending on the drug used.
Finasteride → ↓ 5-alpha-reductase → ↓ dihydrotestosterone → reduced follicular miniaturization.
Eflornithine → ornithine decarboxylase inhibition → slower unwanted hair growth; hydroquinone → reduced melanogenesis → lightening of hyperpigmented skin.
3. AIM HIGH-YIELD INTEGRATION REVIEW
abnormal follicular keratinization → retinoids; bacterial/inflammatory component → benzoyl peroxide or antibiotics; severe disease → isotretinoin with major teratogenic concern.
TLR7 activation increases local immunity, whereas calcineurin inhibition decreases T-cell activity.
permethrin disrupts parasite sodium-channel function → paralysis → treatment of scabies and pediculosis; local burning or stinging may occur.
hydroquinone reduces melanin synthesis but prolonged misuse may cause ochronosis; monobenzone can cause permanent depigmentation through melanocyte destruction.
treatment targets epidermal hyperproliferation and immune inflammation; calcipotriol acts on keratinocytes, while systemic immunosuppressive drugs require toxicity awareness.
reduced inflammatory gene expression → less erythema and pruritus; prolonged potent therapy → skin atrophy, striae and increased systemic absorption risk.
salicylic acid reduces stratum corneum cohesion; pramoxine decreases sensory nerve transmission; menthol reduces itch through cooling pathways.
minoxidil promotes hair growth, finasteride lowers DHT, eflornithine slows unwanted hair growth, and topical 5-FU inhibits thymidylate synthase in proliferating abnormal epidermal cells.