Paper I
2024 March (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Enumerate opioid receptors. Write the uses, adverse effects and contra indications for Morphine. Briefly describe the management of Morphine poisoning. (1+5+2)

Q58 marksShort Essays

Answer

Opioid receptors: mu (μ), kappa (κ), delta (δ) — G-protein-coupled receptors; the mu receptor is responsible for most of morphine’s analgesic effect and its major adverse effects.

Uses of morphine: severe acute pain (post-operative, MI), chronic cancer pain (WHO analgesic ladder, step 3), acute left ventricular failure/pulmonary edema (preload reduction), pre-anesthetic medication, cough suppression and diarrhea control via congeners.

Adverse effects: respiratory depression (most dangerous, dose-related), constipation (no tolerance develops), nausea/vomiting, sedation, tolerance and dependence with chronic use, histamine-mediated hypotension/flushing/pruritus, miosis.

Contraindications: head injury/raised intracranial pressure (CO₂ retention worsens ICP, miosis masks the pupillary sign of deterioration), bronchial asthma (histamine-mediated bronchospasm), severe hepatic impairment, labour/near-term pregnancy (neonatal respiratory depression), concurrent MAO inhibitors.

Management of morphine poisoning:

  • Maintain airway, breathing, circulation — assisted ventilation/oxygen for respiratory depression, the immediate life-threatening priority.
  • Naloxone (specific opioid antagonist) — IV, titrated to reverse respiratory depression; repeated dosing/infusion often needed since naloxone’s duration is shorter than morphine’s.
  • Gastric decontamination if oral ingestion and presentation is early.
  • Supportive care and continuous monitoring, given the risk of re-sedation once naloxone wears off.

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