Midazolam is preferred over diazepam for procedural sedation in the ICU primarily because:
- A It has a higher volume of distribution and longer half-life
- B It undergoes hepatic conjugation to inactive metabolites with a shorter context-sensitive half-time ✓
- C It does not bind to GABA-A receptors
- D It is a partial agonist at benzodiazepine receptors
Correct answer: B. It undergoes hepatic conjugation to inactive metabolites with a shorter context-sensitive half-time
Explanation
Midazolam undergoes rapid hydroxylation by CYP3A4 to 1-hydroxymidazolam, which is then conjugated to an inactive glucuronide; its context-sensitive half-time is shorter than that of diazepam after brief infusions. Diazepam and its active metabolite desmethyldiazepam have very long elimination half-lives (>36 h), causing prolonged sedation in the critically ill. Both act on GABA-A receptors as full agonists.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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