Which morphine metabolite is active?

Which morphine metabolite is active?

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

Answer: (A)

Morphine is processed in the liver to form glucuronide conjugates, and among these, one retains analgesic activity. Morphine-6-glucuronide is the active metabolite that continues to stimulate mu-opioid receptors and contribute to pain relief, sometimes even with greater potency than morphine itself. This metabolite can accumulate in patients with reduced renal function, prolonging analgesia and potentially increasing side effects. In contrast, morphine-3-glucuronide does not produce analgesia and may be associated with other, nonanalgesic effects; morphine-2-glucuronide is not a major clinically relevant active metabolite; and morphine sulfate is the parent drug, not a metabolite. Therefore, the active metabolite is morphine-6-glucuronide.

Morphine is processed in the liver to form glucuronide conjugates, and among these, one retains analgesic activity. Morphine-6-glucuronide is the active metabolite that continues to stimulate mu-opioid receptors and contribute to pain relief, sometimes even with greater potency than morphine itself. This metabolite can accumulate in patients with reduced renal function, prolonging analgesia and potentially increasing side effects. In contrast, morphine-3-glucuronide does not produce analgesia and may be associated with other, nonanalgesic effects; morphine-2-glucuronide is not a major clinically relevant active metabolite; and morphine sulfate is the parent drug, not a metabolite. Therefore, the active metabolite is morphine-6-glucuronide.