Fentanyl is primarily metabolized to which inactive metabolite?

Fentanyl is primarily metabolized to which inactive metabolite?

• A. Norfentanyl (inactive)
• B. Nor fentanyl (active)
• C. Fentanyl glucuronide
• D. Fentanyl carboxylate

Answer: (A)

Fentanyl is mainly processed in the liver by CYP3A4, which removes a methyl group to form norfentanyl. This metabolite is inactive, so norfentanyl represents the primary inactive product of fentanyl metabolism. While norfentanyl can undergo further conjugation to a glucuronide, the key point is that the main metabolite produced is norfentanyl and it lacks analgesic activity. The option suggesting an active form of norfentanyl isn’t correct because norfentanyl does not have meaningful opioid activity. The other listed metabolites exist in metabolism, but they are not the principal products of fentanyl biotransformation.

Fentanyl is mainly processed in the liver by CYP3A4, which removes a methyl group to form norfentanyl. This metabolite is inactive, so norfentanyl represents the primary inactive product of fentanyl metabolism. While norfentanyl can undergo further conjugation to a glucuronide, the key point is that the main metabolite produced is norfentanyl and it lacks analgesic activity. The option suggesting an active form of norfentanyl isn’t correct because norfentanyl does not have meaningful opioid activity. The other listed metabolites exist in metabolism, but they are not the principal products of fentanyl biotransformation.