Which sequence correctly lists these opioids from most potent to least potent?

Which sequence correctly lists these opioids from most potent to least potent?

• A. Sufentanil, Fentanyl, Remifentanil, Alfentanil, Hydromorphone, Morphine, Meperidine
• B. Fentanyl, Sufentanil, Remifentanil, Alfentanil, Hydromorphone, Morphine, Meperidine
• C. Sufentanil, Fentanyl, Alfentanil, Remifentanil, Hydromorphone, Morphine, Meperidine
• D. Sufentanil, Remifentanil, Fentanyl, Alfentanil, Hydromorphone, Morphine, Meperidine

Answer: (A)

Potency reflects how small a dose is needed to produce analgesia—the higher the potency, the less drug is required. Among these opioids, sufentanil is the most potent because of its very high receptor affinity and lipophilicity, so a tiny amount provides analgesia. Fentanyl follows as the next most potent. Remifentanil is also highly potent, but in this ranking it sits below fentanyl and above alfentanil, consistent with its strong but slightly lower potency compared with fentanyl. Alfentanil is less potent than fentanyl and remifentanil, reflecting its lower receptor affinity. Hydromorphone is more potent than morphine, so it sits above morphine in strength. Morphine, in turn, is more potent than meperidine. Putting that together gives: sufentanil, fentanyl, remifentanil, alfentanil, hydromorphone, morphine, meperidine.

Potency reflects how small a dose is needed to produce analgesia—the higher the potency, the less drug is required. Among these opioids, sufentanil is the most potent because of its very high receptor affinity and lipophilicity, so a tiny amount provides analgesia. Fentanyl follows as the next most potent. Remifentanil is also highly potent, but in this ranking it sits below fentanyl and above alfentanil, consistent with its strong but slightly lower potency compared with fentanyl. Alfentanil is less potent than fentanyl and remifentanil, reflecting its lower receptor affinity. Hydromorphone is more potent than morphine, so it sits above morphine in strength. Morphine, in turn, is more potent than meperidine. Putting that together gives: sufentanil, fentanyl, remifentanil, alfentanil, hydromorphone, morphine, meperidine.