Paper II
Question
(
- (a) Enumerate the drugs used for Psoriasis and explain the pharmacological basis for their use. (
- (b) Penicillin.
Answer
a) Drugs for psoriasis and pharmacological basis
- Topical corticosteroids — reduce inflammation and keratinocyte proliferation via genomic anti-inflammatory action; first-line for mild-moderate localized disease.
- Topical Vitamin D analogues (Calcipotriol) — bind vitamin D receptors in keratinocytes, normalizing their abnormally rapid proliferation and differentiation, the core pathological process in psoriasis.
- Coal tar and Dithranol — reduce epidermal cell turnover through poorly understood but established antiproliferative and anti-inflammatory effects; older, effective, but cosmetically less acceptable options.
- Methotrexate — a folate antagonist, at low doses acts as an anti-proliferative/immunomodulatory agent, inhibiting the excessive keratinocyte turnover and T-cell-driven inflammation; used for moderate-severe/refractory disease.
- Biologic agents (TNF-alpha inhibitors — Etanercept, Infliximab; IL-17/IL-23 inhibitors) — directly neutralize the specific inflammatory cytokines driving psoriatic plaque formation; used for severe disease refractory to conventional therapy.
- Phototherapy (UVB, PUVA) — UV-induced apoptosis of pathogenic T-cells and reduced keratinocyte proliferation, for widespread disease.
b) Penicillin The prototype beta-lactam. MOA: binds penicillin-binding proteins (transpeptidases), inhibiting peptidoglycan cross-linking, causing bactericidal cell wall failure in dividing organisms. Uses: Streptococcus pyogenes infections, syphilis, meningococcal infections. Adverse effects: hypersensitivity reactions (including anaphylaxis), Jarisch-Herxheimer reaction when treating syphilis.