Which morphine metabolite is inactive?

Which morphine metabolite is inactive?

• A. Morphine-3-glucuronide
• B. Morphine-6-glucuronide
• C. Morphine-2-glucuronide
• D. Morphine sulfate

Answer: (A)

Morphine is mainly metabolized in the liver into two glucuronide metabolites with very different effects. Morphine-6-glucuronide is an active mu-opioid agonist and contributes to analgesia, sometimes even more potently than morphine itself. Morphine-3-glucuronide, in contrast, does not provide analgesia and is considered inactive in terms of pain relief (though at very high concentrations it can cause neuroexcitatory effects). The parent drug, morphine sulfate, is the source of analgesia. Therefore, the inactive metabolite among these is morphine-3-glucuronide.

Morphine is mainly metabolized in the liver into two glucuronide metabolites with very different effects. Morphine-6-glucuronide is an active mu-opioid agonist and contributes to analgesia, sometimes even more potently than morphine itself. Morphine-3-glucuronide, in contrast, does not provide analgesia and is considered inactive in terms of pain relief (though at very high concentrations it can cause neuroexcitatory effects). The parent drug, morphine sulfate, is the source of analgesia. Therefore, the inactive metabolite among these is morphine-3-glucuronide.