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

Question

A 60-year-old male with a history of hypertension and diabetes presents to the emergency department with crushing chest pain radiating to his left arm, suggestive of acute myocardial infarction (AMI). He is anxious, and his pain is rated as 9/10. The patient is stabilized with oxygen and other supportive measures but his chest pain persists.

  • (a) Mention the analgesic of choice in this patient with route of administration and pharmacological basis for the same. 4 mark(s)
  • (b) Mention two adverse effects of the same along with the involved receptor. 2 mark(s)
  • (c) Enumerate two other uses of the preferred analgesic. 2 mark(s)
  • (d) Mention two antagonists that can be used in case the patient encounters overdosage with route of administration. 2 mark(s)
Q310 marksEssays

Answer

a) Analgesic of choice, route, and pharmacological basis Morphine, given IV (rapid, titratable onset — appropriate for severe, ongoing pain in a monitored emergency setting). Basis: acts on mu-opioid receptors, hyperpolarizing neurons in the pain pathway to produce potent analgesia; also causes venodilation (reducing preload/myocardial wall tension) and reduces the pain-driven sympathetic surge (tachycardia, hypertension) that would otherwise increase myocardial oxygen demand and worsen ischemia — addressing both this patient’s pain and the hemodynamic stress it is causing.

b) Two adverse effects, with the involved receptor

  • Respiratory depression — mu receptor (reduced brainstem sensitivity to CO₂).
  • Constipation — mu receptor (reduced GI motility; no tolerance develops to this effect).

c) Two other uses of morphine Chronic cancer pain (WHO analgesic ladder, step 3); acute left ventricular failure/pulmonary edema (preload reduction via venodilation).

d) Two antagonists for overdose, with route Naloxone — IV, rapid-onset, titrated to reverse respiratory depression (repeated dosing/infusion often needed given its shorter duration than morphine’s). Naltrexone — oral, longer-acting, used for relapse prevention/maintenance rather than acute reversal.

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