Remifentanil is an ultra-short-acting opioid used in TIVA. Which metabolic pathway accounts for its extremely short duration of action and why is it unique among opioids?
- A Hepatic CYP3A4 first-pass metabolism; rapid oral bioavailability
- B Renal glomerular filtration; dose reduction required in CKD
- C Ester hydrolysis by non-specific blood and tissue esterases, organ-independent; constant CSHL of ~3–4 minutes regardless of infusion duration ✓
- D Plasma pseudocholinesterase hydrolysis; prolonged in hepatic failure
Explanation
Remifentanil contains an ester linkage that is hydrolysed by non-specific esterases in blood and tissues (not pseudocholinesterase), producing an essentially inactive carboxylate metabolite. This is organ-independent, making it safe in hepatic and renal failure. The elimination half-life is approximately 3–10 minutes with a remarkably stable context-sensitive half-life of ~3–4 minutes regardless of infusion duration. This predictability allows precise titration but means analgesia is lost immediately on discontinuation — requiring a transition analgesic plan (morphine, paracetamol, NSAIDs, ketamine) before emergence.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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