Question

Which of the following statements about opioid receptor antagonists is false?

• A. Naloxone can be used for treatment of opioid induced constipation
• B. Naltrexone may be used for treatment of alcohol dependence
• C. Nalmefene has a longer half life than naloxone
• D. Naloxone is more potent than naltrexone

Hint:

Compare potency and duration: which antagonist is short acting and parenteral versus orally active and long lasting?

Answer 1

The Correct Option is D

This is a negative-stem question, so the right pick is the wrong fact. Let us audit each claim about opioid antagonists.

Naloxone for constipation holds up: when given in forms that stay in or act mainly on the gut, it blocks intestinal opioid receptors and eases opioid induced constipation while sparing central pain control, so statement one is correct. Naltrexone for alcohol dependence is also correct, as it dampens the reward and craving linked to drinking and is licensed for that use. Nalmefene having a longer half life than naloxone is true as well; nalmefene lasts many hours whereas naloxone fades within an hour or two, which is exactly why naloxone often needs repeat dosing in overdose.

That leaves the claim that naloxone is more potent than naltrexone. In reality naltrexone is the more potent, orally active, and longer lasting of the two; naloxone is short acting and used by injection in emergencies. So this statement is the false one and therefore the answer.
\[\boxed{\text{Naloxone is more potent than naltrexone}}\]