Which statement about alfentanil is true?

Which statement about alfentanil is true?

• A. It has a slower onset compared to fentanyl.
• B. It has a larger volume of distribution than fentanyl.
• C. It is cleared primarily by renal excretion unaffected by CYP450.
• D. It has lower potency than fentanyl (1/5-1/10).

Answer: (D)

Alfentanil is a fentanyl analogue that acts very quickly but is less potent than fentanyl. Potency reflects how much drug is needed to achieve a given effect; alfentanil requires a larger dose to produce the same analgesia as fentanyl, about one-fifth to one-tenth as potent. That’s why the true statement is that alfentanil has lower potency than fentanyl. Its onset is actually rapid, not slower, contributing to its use for quick anesthetic induction. It does not have a larger volume of distribution than fentanyl; in fact, it tends to have a smaller Vd due to differences in lipophilicity. Its clearance is primarily hepatic metabolism via CYP450 (CYP3A4), not renal excretion independent of CYP450.

Alfentanil is a fentanyl analogue that acts very quickly but is less potent than fentanyl. Potency reflects how much drug is needed to achieve a given effect; alfentanil requires a larger dose to produce the same analgesia as fentanyl, about one-fifth to one-tenth as potent. That’s why the true statement is that alfentanil has lower potency than fentanyl.

Its onset is actually rapid, not slower, contributing to its use for quick anesthetic induction. It does not have a larger volume of distribution than fentanyl; in fact, it tends to have a smaller Vd due to differences in lipophilicity. Its clearance is primarily hepatic metabolism via CYP450 (CYP3A4), not renal excretion independent of CYP450.