Skin Pharmacology

Question 1

What is the mainstay of treatment for eczematous dermatitis? What are some other options?

Answer 1

• topical corticosteroids are mainstay
• MOA: bind to lipocortin-1, inhibiting phospholipase A2 from activating arachidonic acid (so no LTs and PGs); they also inhibit IL-2 by inhibiting NF-kB
• (use antihistamines for mild cases such as urticaria and also to relieve pruritus)
• other option: topical calcineurin inhibitors
• MOA: inhibit calcineurin to prevent NFAT transcription of IL-2 gene

Question 2

What is an extremely potent topical corticosteroid? What about a much weaker one?

Answer 2

• potent: betamethasone
• weak: hydrocortisone
• (corticosteroids bind to lipocortin-1, inhibiting phospholipase A2 from activating arachidonic acid, resulting in lowered LTs and PGs; they also inhibit IL-2 by inhibiting NF-kB)

Question 3

What are the two major topical calcineurin inhibitors?

Answer 3

• tacrolimus and pimecrolimus

- (calcineurin inhibitors inhibit calcineurin to prevent NFAT transcription of IL-2 gene)

Question 4

What are the mainstay treatments for psoriasis? What are some other options?

Answer 4

• topical corticosteroids and calcineurin inhibitors are mainstay
• corticosteroids: bind to lipocortin-1, inhibiting phospholipase A2 from activating arachidonic acid (so no LTs and PGs); they also inhibit IL-2 by inhibiting NF-kB
• calcineurin inhibitors: inhibit calcineurin to prevent NFAT transcription of IL-2 gene
• can also use methotrexate since the keratinocytes are rapidly dividing (blocks dihydrofolate reductase, preventing tetrahydrofolate production)
• other options: monoclonal Abs, vitamin D analogues (via D decreases keratinocyte proliferation), coal tars, salicylic acid (lyses keratinocytes)

Question 5

How do we treat tinea?

Answer 5

• tinea is a fungal skin infection via dermatophytes
• it is treated with antifungals
• azoles and allylamines
• NOT treated with topical corticosteroids

Question 6

How do we treat cutaneous candidiasis?

Answer 6

• candidiasis is via a fungus

- treat with antifungals (azoles, allylamines, nystatin) or topical corticosteroids

Question 7

How do we treat acne vulgaris?

Answer 7

• this is a bacterial infection via Propionibacterium acnes

- treat with clindamycin in gel form (MOA: inhibits bacterial 50S ribosomal subunit)

Question 8

How do we treat impetigo?

Answer 8

• this is a bacterial infection

- treat with mupirocin (inhibits bacterial protein synthesis)

Question 9

How do we treat herpes simplex and herpes zoster?

Answer 9

• these are viral infections
• treat with aciclovir (a guanosine analog that inhibits viral DNA polymerase)
• can add benzoyl peroxide to current regimen for an extra kick

Question 10

What pharmacological treatment is available for some skin cancers?

Answer 10

• Imiquimod is a topical treatment for basal cell carcinoma only (MOA: activates TLR-7 receptors, triggering the release of cytokines INF-alpha, IL-6, TNF-alpha, and activating macrophages; essentially, it stimulates the immune system to attack the carcinoma)
• fluorouracil can be given for actinic keratoses