Acidic Anti-Inflammatory and Antipyretic Analgesics (NSAIDs)

• Mechanism of Action:
  • Peripheral and/or central inhibition of prostaglandin synthesis by blocking cyclooxygenase (COX).
  • Types:
    • Non-selective COX-1 and COX-2 inhibitors.
    • Selective COX-2 inhibitors.
• Effects:
  • Analgesic, anti-inflammatory, antipyretic.
  • Inhibition of platelet aggregation.
• Side Effects:
  • Gastrointestinal: Gastritis, ulcers.
    • Note: Caution with concurrent use of coumarins and steroids.
    • Prevention: Omeprazole 20 mg/day or Misoprostol 3–4 × 200 µg/day.
  • Renal: Reduced renal perfusion with risk of kidney failure, especially in hypovolemia or pre-existing renal damage.
    • Sodium and water retention → Potential worsening of heart failure or edema.
  • Allergic Reactions: Hypotension, dizziness, bronchoconstriction; rarely agranulocytosis.
  • Analgesic-Induced Asthma.
  • Central Nervous System: Headache, dizziness, confusion, hearing disturbances.
  • Selective COX-2 Inhibitors: Increased cardiovascular risks with long-term use (>3 months) in high-risk patients (e.g., CAD, history of myocardial infarction or stroke).
• Indications:
  • Mild pain.
  • Moderate-to-severe pain in combination with opioids (refer to WHO analgesic ladder).
• Contraindications:
  • Absolute: Active gastrointestinal ulcers, significant renal impairment, increased bleeding risk, suspected intracranial bleeding, known allergies, analgesic-induced asthma.
  • Relative: Ulcer history (with gastric protection), cerebral dysfunction.
• COX-2 Inhibitors Specific:
  • Absolute: Coronary artery disease, cerebrovascular disease, heart failure (NYHA II–IV).
  • Relative: Cardiovascular risk factors (e.g., hypertension, smoking, hyperlipidemia, diabetes).

Common NSAID Preparations

Non-Acidic Antipyretic Analgesics (Paracetamol, Metamizol)

• Mechanism of Action:
  • Paracetamol: Inhibits prostaglandin release in the CNS and modulates spinal analgesia.
  • Metamizol: Inhibits activity of C-fibers and spinal neurons; activates pain-inhibitory pathways.
• Effects:
  • Analgesic, antipyretic.
  • Metamizol: Additional spasmolytic effect.
• Side Effects:
  • Paracetamol: Hepatotoxicity, rare agranulocytosis, nephrotoxicity with chronic use.
  • Metamizol: Allergic reactions (rarely anaphylaxis), agranulocytosis (rare cases).
  • Caution: Rapid IV administration may cause hypotension or shock.
• Indications:
  • Mild to moderate pain, fever, NSAID contraindications.
  • Metamizol: Additionally for colic pain.
• Contraindications:
  • Paracetamol: Severe liver damage, glucose-6-phosphate dehydrogenase deficiency.
  • Metamizol: Blood disorders, hepatic porphyria, advanced renal impairment, pyrazolone allergy.

Common Preparations

Flupirtine

• Mechanism of Action:
  • Central pain inhibition by enhancing descending pain control pathways.
  • Muscle relaxation.
• Effects:
  • Analgesic, muscle relaxant.
• Side Effects:
  • Nausea, headache, fatigue, sweating, restlessness, drowsiness, liver dysfunction.
• Indications:
  • Pain associated with increased muscle tone (e.g., back pain, tension headaches).
• Contraindications:
  • Myasthenia gravis, liver damage.
• Dosage:
  • Standard: 3 × 100–200 mg/day.
  • Maximum: 600 mg/day.