After absorption, codeine is rapidly metabolized to what compound?

After absorption, codeine is rapidly metabolized to what compound?

• A. Phencyclidine
• B. Morphine
• C. Methadone
• D. Propoxyphene

Answer: (B)

Codeine is a prodrug that requires hepatic metabolism to become the active analgesic compound. In the liver, the enzyme CYP2D6 converts codeine into morphine, and this morphine is what binds to opioid receptors to produce pain relief. Because the analgesic effect hinges on this conversion, morphine is the best answer as the active metabolite. Genetic differences in CYP2D6 can make some people convert codeine to morphine very quickly, risking toxicity from higher morphine levels, while others convert it slowly and get little pain relief. The other substances listed are not derived from codeine’s metabolism: phencyclidine is a separate dissociative drug, and methadone and propoxyphene are distinct opioids with different metabolic fates.

Codeine is a prodrug that requires hepatic metabolism to become the active analgesic compound. In the liver, the enzyme CYP2D6 converts codeine into morphine, and this morphine is what binds to opioid receptors to produce pain relief. Because the analgesic effect hinges on this conversion, morphine is the best answer as the active metabolite. Genetic differences in CYP2D6 can make some people convert codeine to morphine very quickly, risking toxicity from higher morphine levels, while others convert it slowly and get little pain relief. The other substances listed are not derived from codeine’s metabolism: phencyclidine is a separate dissociative drug, and methadone and propoxyphene are distinct opioids with different metabolic fates.