Questions
3-5 questions in B.Pharm/MBBS semester papers
Difficulty
Medium-Hard
Importance
High yield for University Pharmacy and MBBS pharmacology boards
Overview
Autacoids are local hormones that mediate physiological and pathological processes, while NSAIDs and anti-gout drugs are critical therapeutic agents used to manage inflammation and crystal-induced arthropathy. Mastering this topic is essential as it forms the pharmacological basis for pain management and inflammatory disease treatment in clinical practice.
Histamine and Antihistamines
Histamine is a mediator of allergic responses acting on H1, H2, H3, and H4 receptors. Antihistamines are competitive antagonists that block these receptors to treat conditions like urticaria, motion sickness, and gastric acid secretion.
- H1 blockers: Chlorpheniramine, Cetirizine, Loratadine
- H2 blockers: Ranitidine, Famotidine (used for PUD)
- Triple response of Lewis: Flushing, Flare, Wheal
- First-generation agents cause sedation due to BBB penetration
- Second-generation agents are non-sedating
NSAIDs and COX Inhibitors
Non-steroidal anti-inflammatory drugs exert their effect primarily by inhibiting the cyclooxygenase (COX) enzymes, thereby reducing prostaglandin synthesis. Understanding the selectivity between COX-1 (constitutive) and COX-2 (inducible) is vital for minimizing gastric adverse effects.
- Mechanism: Inhibition of arachidonic acid conversion to prostaglandins
- Non-selective: Aspirin, Ibuprofen, Diclofenac
- COX-2 selective: Celecoxib, Etoricoxib
- Aspirin: Irreversible inhibitor of COX enzymes via acetylation
- Common ADR: Gastric mucosal damage and nephrotoxicity
Anti-Gout Drugs
Gout is characterized by hyperuricemia and the deposition of urate crystals in joints. Treatment focuses on terminating acute attacks and managing chronic uric acid levels through synthesis inhibition or increased excretion.
- Acute gout: Colchicine, NSAIDs
- Xanthine oxidase inhibitor: Allopurinol, Febuxostat
- Uricosuric agent: Probenecid
- Allopurinol mechanism: Competitive inhibition of xanthine oxidase
- Colchicine mechanism: Inhibition of neutrophil migration and tubulin polymerization
Exam Tip
Always link the pharmacological classification to the corresponding receptor or enzyme mechanism, as examiners favor mechanistic explanations over simple lists of drug names.
Common Mistakes
- Confusing the H1 receptor (allergic) and H2 receptor (gastric acid) indications.
- Neglecting the clinical significance of irreversible COX inhibition by aspirin compared to other NSAIDs.
- Failing to distinguish between drugs for acute gout (anti-inflammatory) and chronic gout (uric acid lowering).
More Revision Notes
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