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Pharmacology · single question

Codeine is classified as what type of drug?

  1. Active full opioid agonist
  2. Opioid antagonist
  3. Partial opioid agonist
  4. A prodrug that requires conversion to morphine for its analgesic effect
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Correct answer: D. A prodrug that requires conversion to morphine for its analgesic effect

  • A. Incorrect. Codeine itself has minimal opioid receptor affinity and requires metabolic activation.
  • B. Incorrect. Opioid antagonists (naloxone, naltrexone) BLOCK opioid receptors. Codeine (via morphine) activates them.
  • C. Incorrect. Buprenorphine is a partial opioid agonist. Codeine's activity comes entirely from its morphine conversion.
  • D. Correct. Codeine is a PRODRUG. It is metabolized by CYP2D6 to MORPHINE, which is the active analgesic. CYP2D6 ultra-rapid metabolizers risk toxicity; poor metabolizers get minimal analgesia. This is why codeine is contraindicated in children post-tonsillectomy.

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