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Overview of NSAIDs and Their Effects

Apr 25, 2025

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NSAIDs: Non-Steroidal Anti-Inflammatory Drugs

Physiology of Arachidonic Acid

  • Arachidonic acid is a precursor to prostanoids (prostaglandins, prostacyclins, thromboxanes).
  • Found in cell membranes; released by phospholipase A2.
  • Converted into inflammatory mediators by cyclooxygenase enzymes (COX-1 and COX-2).

Function of COX Enzymes

  • COX-1: Converts arachidonic acid into thromboxane A2 (platelet activator and vasoconstrictor) and prostaglandins (gastric protection).
  • COX-2: Produces prostacyclins (vasodilation, inhibits platelet aggregation) and inflammatory prostaglandins (increased vascular permeability, pain sensitivity, fever).

Types of NSAIDs

  • Non-selective NSAIDs: Reversibly inhibit COX-1 and COX-2 (e.g., Ibuprofen, Diclofenac, Ketorolac, Indomethacin, Meloxicam, Piroxicam, Naproxen).
  • Aspirin: Irreversibly inhibits COX-1 and COX-2; low-dose for anti-platelet effect; high-dose for anti-inflammatory.
  • COX-2 Selective NSAIDs: Celecoxib, primarily inhibits COX-2 (less gastric side effects, increased cardiovascular risk).

Side Effects of NSAIDs

  • Gastrointestinal: Gastric erosion, ulcers due to reduced mucus secretion.
    • Often given with proton pump inhibitors or Misoprostol.
  • Bleeding: Reduced thromboxane A2 leads to increased bleeding risk.
  • Renal:
    • Increased blood pressure (lower sodium excretion, reduced kidney blood flow).
    • Acute kidney injury, acute interstitial nephritis.
    • Aplastic anemia (mainly with Indomethacin), neutropenia.
    • Hyperkalemia due to decreased sodium delivery and altered potassium excretion.

Contraindications

  • Chronic kidney disease, dehydration, cirrhosis, heart failure.
  • Third trimester of pregnancy (risk of closing ductus arteriosus).

Special Considerations

  • Aspirin Toxicity: Leads to respiratory alkalosis followed by metabolic acidosis.
    • Charcoal and bicarbonate as antidotes.
  • Reye's Syndrome: Encephalopathy and hepatic failure in children with aspirin.

Conclusion

NSAIDs are widely used drugs with various effects based on their inhibition of COX enzymes. It's essential to consider their side effects, contraindications, and specific patient conditions when using them.

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