Paper I
2025 March (Supplementary (SAY)) (2019 Scheme) · 100 marks · 180 min

Question

A 55-year-old male patient was recently diagnosed as suffering from hepatocellular carcinoma with metastases to bone. He complains of severe, excruciating pain in the abdomen and spine. He has complained of sleeplessness and mood swings for the past one month. The oncologist prescribes him an opioid analgesic drug to relieve his pain and also induce sleep and reduce apprehension of pain.

  • (a) Classify opioid analgesics. 3 mark(s)
  • (b) Explain the Mechanism of action of Morphine and its pharmacological actions. 4 mark(s)
  • (c) Enumerate any THREE clinical uses and adverse effects of Morphine. 3 mark(s)
Q310 marksEssays

Answer

a) Classification of opioid analgesics

BasisClassExamples
SourceNaturalMorphine, Codeine
SemisyntheticDiacetylmorphine (heroin), Buprenorphine
SyntheticPethidine, Fentanyl, Methadone, Tramadol
Receptor actionPure agonistMorphine, Fentanyl
Partial agonistBuprenorphine
Agonist-antagonistPentazocine
Pure antagonistNaloxone

b) Mechanism of action and pharmacological actions of Morphine Mechanism: morphinebinds mu (μ) opioid receptorsGi-protein coupling↓cAMP → neuronal hyperpolarization → reduced pain-signal transmission and perception.

Actions: analgesia (most effective against dull, continuous visceral pain — fitting this patient’s bone/abdominal cancer pain), sedation and reduced apprehension of pain (addressing his sleeplessness and mood swings), euphoria, respiratory depression, miosis, antitussive action, reduced GI motility (constipation), nausea/vomiting (CTZ stimulation), histamine release.

c) Three clinical uses Severe cancer pain (as in this patient), acute pulmonary edema (preload reduction via venodilation), pre-anesthetic medication.

Three adverse effects Respiratory depression (dose-related, most dangerous), constipation (no tolerance develops), tolerance and physical/psychological dependence with chronic use.

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