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Analgesics & NSAIDs: Understanding Pain Relief & Inflammation

Analgesics and NSAIDs: Mechanisms, Uses, and Safety

Analgesics relieve pain. NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) are a subclass with anti-inflammatory, antipyretic, and analgesic properties.

Classification

ClassExamplesKey Features
Non-opioid analgesicsAcetaminophen (paracetamol)Central COX inhibition; minimal anti-inflammatory; no antiplatelet; hepatotoxic in overdose
Traditional NSAIDs (non-selective COX)Ibuprofen, naproxen, diclofenac, indomethacin, ketorolac, aspirinCOX-1 & COX-2 inhibition; anti-inflammatory, antipyretic, antiplatelet (aspirin irreversible); GI, renal, CV risks
COX-2 selective inhibitorsCelecoxib, etoricoxibPreferential COX-2 blockade; lower GI risk; CV risk persists

Mechanism

NSAIDs inhibit cyclooxygenase (COX) → ↓ prostaglandin synthesis → ↓ inflammation, pain sensitization, fever. COX-1: constitutive (GI mucosa, platelets, renal perfusion). COX-2: inducible (inflammation).

Common Indications

  • Musculoskeletal pain (back, osteoarthritis, sprains)
  • Headache, migraine
  • Dysmenorrhea
  • Postoperative, dental pain
  • Fever
  • Rheumatoid arthritis, ankylosing spondylitis (chronic NSAID use)

Major Adverse Effects

  • GI: Dyspepsia, ulcers, bleeding (COX-1 inhibition). Risk ↑ with age, history, steroids, anticoagulants, H. pylori.
  • Renal: Afferent arteriolar constriction → ↓ GFR. Risk in CKD, dehydration, heart failure, elderly.
  • Cardiovascular: ↑ Thrombotic events (MI, stroke) — all NSAIDs except low-dose aspirin. Risk ↑ with dose/duration.
  • Hepatic: Rare idiosyncratic injury (diclofenac highest).
  • Hematologic: Platelet dysfunction (reversible except aspirin).

Safe Use Principles

  • Lowest effective dose, shortest duration.
  • Take with food (GI protection).
  • Consider PPI co-therapy if high GI risk.
  • Avoid in late pregnancy (3rd trimester).
  • Monitor renal function if chronic use.
  • Check drug interactions (anticoagulants, ACEi/ARBs, diuretics, lithium, methotrexate).

Acetaminophen preferred for patients with GI/CV/renal risk factors needing analgesia without anti-inflammatory effect.

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