A single induction dose of etomidate (0.3 mg/kg IV) causes transient adrenocortical suppression. The specific enzyme inhibited is:

• A 21-hydroxylase
• B Cholesterol side-chain cleavage enzyme (CYP11A1)
• C 3-beta-hydroxysteroid dehydrogenase
• D 11-beta-hydroxylase ✓

Explanation

Etomidate inhibits 11-beta-hydroxylase (CYP11B1), the enzyme that converts 11-deoxycortisol to cortisol in the adrenal cortex. This causes a dose-dependent reduction in cortisol synthesis lasting 4–8 hours after a single induction dose, and potentially days with continuous infusion (as in ICU sedation). 21-hydroxylase is the enzyme most commonly deficient in congenital adrenal hyperplasia. Cholesterol side-chain cleavage and 3-beta-HSD are other steroidogenic enzymes not primarily targeted by etomidate.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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