Intraoperative fentanyl dose is commonly used for analgesia in adults, and how does it compare with remifentanil?

• A. Typically 1-2 mcg/kg; fentanyl has a longer duration than remifentanil and accumulates with longer infusions.
• B. Typically 0.1-0.2 mcg/kg; shorter duration.
• C. Typically 5-10 mg; no accumulation.
• D. Typically 50-100 mcg; same duration as remifentanil.

Answer: (A)

Intraoperative analgesia with fentanyl versus remifentanil hinges on how long each drug lasts in the body and how they are cleared. Fentanyl is highly lipophilic, so after a bolus or infusion it redistributes into tissues and has a longer duration of action. With longer infusions, it can accumulate in the body, prolonging recovery and increasing the potential for postoperative sedation or respiratory depression. Remifentanil, by contrast, is rapidly broken down by nonspecific esterases, giving it an ultra-short, highly titratable offset even after long infusions, with essentially no meaningful accumulation.

The typical fentanyl intraoperative dose is about 1–2 mcg/kg, which aligns with the idea of a longer-acting analgesic that can accumulate if the infusion is extended. That’s why the statement noting 1–2 mcg/kg and describing longer duration with accumulation is correct.

Other options fail because they either propose an unrealistically low fentanyl dose, imply milligram amounts, or suggest that fentanyl has a duration similar to remifentanil. Fentanyl’s duration is not shorter, and remifentanil’s duration is not equivalent to fentanyl’s.