Topic 20 — Eicosanoids, Dermatologic Pharmacotherapy and Selected Herbal Medicines

Connect the major pharmacological mechanisms, therapeutic choices and safety relationships for rapid KMU-focused revision.

Concept Integration structure follows the supplied AIM instructions. :contentReference[oaicite:0]{index=0}

1. THE TOPIC IN ONE CONNECTED FLOW

This topic links three practical pharmacology decisions: understanding how locally produced eicosanoids generate organ effects, selecting the correct drug and formulation for common skin conditions, and recognizing that herbal products can also produce clinically important pharmacological effects and interactions.

Arachidonic Acid
Cell-membrane lipid precursor for eicosanoids

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Enzyme Pathways
COX → prostaglandins, PGI₂, TXA₂
LOX → leukotrienes

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Receptor-Mediated Effects
Vascular, platelet, uterine, gastric and ocular responses

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Therapeutic Analogues
Glaucoma, gastric protection, uterine effects, ductal patency and pulmonary vasodilation

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Clinical Drug Selection
Match drug mechanism and topical vehicle to the clinical problem

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Safety Check
Retinoid teratogenicity, local irritation and herbal–drug interactions

Skin treatment branch:

Nature of lesion → suitable vehicle → scabies, acne or psoriasis drug → therapeutic effect → characteristic adverse effect or caution

Herbal-product branch:

Herbal supplement → biologically active constituent → intended effect → interaction with conventional medicine → altered clinical response

2. KEY CLINICAL CONNECTIONSProstanoid Balance and Clinical Effect

PGI₂ → vasodilation + reduced platelet aggregation → protection against excessive platelet activity

TXA₂ → vasoconstriction + platelet aggregation → reinforcement of hemostasis

Dermatologic Vehicle Selection

Dry, thick, scaly lesion → occlusive ointment → increased hydration and drug penetration

Hairy, extensive or exudative area → gel, lotion or wet dressing → easier application and less unwanted occlusion

Retinoids: Benefit Versus Safety

Isotretinoin → suppresses sebaceous gland activity → major improvement in severe acne → strong teratogenic risk

Acitretin → normalizes keratinocyte differentiation → benefit in psoriasis → prolonged teratogenic concern

Herbal Medicines Are Pharmacologically Active

Garlic → reduced platelet aggregation → added bleeding risk with aspirin or warfarin

Ginseng or Coenzyme Q10 → interaction with conventional therapy → glucose or anticoagulant response may change

3. AIM HIGH-YIELD INTEGRATION REVIEW

⭐ Arachidonic acid → COX pathway → prostaglandins, PGI₂ and TXA₂: the final organ effect depends on the mediator and its receptor distribution.

⭐ PGI₂ and TXA₂ have opposing platelet–vascular actions: PGI₂ inhibits aggregation and dilates vessels, whereas TXA₂ promotes aggregation and vasoconstriction.

Prostaglandin analogues → increased aqueous humor outflow → lower intraocular pressure: latanoprost, travoprost, tafluprost and related agents therefore have an important role in glaucoma.

Lesion character → vehicle selection: ointments favor dry thick lesions, while lotions and gels suit broad or hairy areas and wet dressings help exudative lesions.

Scabies therapy → adequate body-surface application → mite eradication: treatment failure may occur when topical scabicides are applied only to visible itchy lesions.

⭐ Acne mechanism → targeted therapy: benzoyl peroxide reduces Cutibacterium acnes, tretinoin normalizes follicular keratinization, and isotretinoin strongly suppresses sebaceous activity.

⭐ Systemic retinoids → strong therapeutic benefit + major reproductive caution: isotretinoin in severe acne and acitretin in psoriasis are important teratogens.

Herbal product → real pharmacological effect → potential drug interaction: garlic may increase bleeding with antithrombotic drugs, ginseng may modify glucose or CNS effects, and Coenzyme Q10 may reduce warfarin’s anticoagulant action.

AIM Exam Trap:
Do not confuse PGI₂ with TXA₂: prostacyclin inhibits platelet aggregation and causes vasodilation, while thromboxane A₂ promotes platelet aggregation and vasoconstriction.

Topic 20 — Eicosanoids, Dermatologic Pharmacotherapy and Selected Herbal Medicines

1. THE TOPIC IN ONE CONNECTED FLOW

2. KEY CLINICAL CONNECTIONSProstanoid Balance and Clinical Effect

3. AIM HIGH-YIELD INTEGRATION REVIEW

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