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Pharmacology · single question

Methadone is used in the management of patients with morphine or heroin dependence. What is the principal reason it is chosen?

  1. It is a long-acting oral opioid that suppresses withdrawal and craving without producing the euphoric peaks of injected opioids
  2. It produces no physical dependence at all
  3. It reverses opioid overdose by displacing opioids from the receptor
  4. It has no opioid receptor activity and therefore no abuse potential
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Correct answer: A. It is a long-acting oral opioid that suppresses withdrawal and craving without producing the euphoric peaks of injected opioids

  • A. CORRECT. METHADONE is a full mu-opioid agonist with a long half-life (roughly 24–36 hours) and oral administration. That pharmacokinetic profile produces stable plasma levels that block withdrawal and craving while avoiding the rapid rise-and-fall that drives the euphoric 'rush' and the reinforcement cycle. It substitutes a controlled, supervised, legal exposure for an uncontrolled one — harm reduction, not cure.
  • B. Methadone DOES produce physical dependence — that is precisely the point of substitution therapy. Abrupt discontinuation causes a withdrawal syndrome, which is why tapering must be supervised.
  • C. That describes NALOXONE, a competitive opioid ANTAGONIST used for overdose reversal. Methadone is an agonist and would worsen an overdose.
  • D. Methadone is a full mu-agonist with real abuse potential, which is why it is dispensed under strict federal regulation in the United States.

Note: Distinguish the three: METHADONE = long-acting full agonist. BUPRENORPHINE = partial agonist with a ceiling on respiratory depression. NALOXONE/NALTREXONE = antagonists. Chairside caution: never give an opioid analgesic to a patient on methadone maintenance without consulting their treatment program.

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