A patient becomes excessively sedated during midazolam-fentanyl sedation for a dental procedure. Flumazenil 0.2 mg IV reverses the benzodiazepine component. What is the most important limitation of flumazenil in this setting?

• A It must be given as a continuous infusion at 1 mg/kg/hour
• B It has a longer duration than midazolam, causing oversedation on rebound
• C It reliably reverses all degrees of sedation including general anaesthesia
• D It does not reverse fentanyl-induced respiratory depression ✓

Explanation

Flumazenil is a competitive antagonist at the benzodiazepine site of the GABA-D receptor and has no action at opioid receptors, so opioid-induced respiratory depression persists and needs naloxone. Its elimination half-time is shorter than that of most benzodiazepines, so resedation can occur, which is the opposite of option B. It incompletely reverses deep sedation and is not infused at 1 mg/kg/hour.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

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