Which characteristic contributes to remifentanil's short duration of action?

Which characteristic contributes to remifentanil's short duration of action?

• A. Expression of mu receptors is low
• B. Metabolism by plasma esterases
• C. High protein binding
• D. Poor lipid solubility

Answer: (B)

Remifentanil’s ultra-short action is due to rapid inactivation by plasma esterases. The molecule contains an ester bond that is quickly hydrolyzed by non-specific esterases in blood and tissues to an inactive metabolite, so clearance is very fast and the duration remains short even with prolonged infusions. This makes its effect largely independent of liver or kidney function, unlike other opioids that depend on hepatic metabolism or redistribution for termination. Other factors like receptor expression or protein binding play roles in potency or distribution, but they don’t drive the ultra-short duration; for example, high protein binding would tend to prolong action, and poor lipid solubility would slow CNS entry rather than shorten duration.

Remifentanil’s ultra-short action is due to rapid inactivation by plasma esterases. The molecule contains an ester bond that is quickly hydrolyzed by non-specific esterases in blood and tissues to an inactive metabolite, so clearance is very fast and the duration remains short even with prolonged infusions. This makes its effect largely independent of liver or kidney function, unlike other opioids that depend on hepatic metabolism or redistribution for termination. Other factors like receptor expression or protein binding play roles in potency or distribution, but they don’t drive the ultra-short duration; for example, high protein binding would tend to prolong action, and poor lipid solubility would slow CNS entry rather than shorten duration.