A neurosurgical team uses an opioid infusion titrated to depth of anaesthesia, allowing rapid awakening for early neurological assessment. Even after 8 hours of continuous infusion, the patient resumes spontaneous breathing within minutes of stopping the drug. Which pharmacokinetic property explains this?

• A High lipid solubility with redistribution to adipose tissue
• B First-order elimination with a very large volume of distribution
• C Active secretion into bile followed by enterohepatic cycling
• D Hydrolysis by nonspecific blood and tissue esterases ✓

Explanation

Remifentanil contains an ester linkage and is cleared by widespread nonspecific plasma and tissue esterases rather than hepatic metabolism. Its context-sensitive half-time stays around 3 to 5 minutes irrespective of infusion duration, so recovery is equally rapid after short or prolonged infusions. Alfentanil and sufentanil depend on hepatic clearance, so their context-sensitive half-times rise steeply with longer infusions, which kills that distractor.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.