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[Pharmacology](https://durgical.com/en/pharmacology/) · [Adrenal steroid synthesis inhibitors](https://durgical.com/en/pharmacology/classes/adrenal-steroid-synthesis-inhibitors/)

# Metyrapone

A blocker of the last step of cortisol synthesis. It tests pituitary ACTH reserve and can lower cortisol in Cushing syndrome.

Updated 2026-11-01

- Class: [Adrenal steroid synthesis inhibitors](https://durgical.com/en/pharmacology/classes/adrenal-steroid-synthesis-inhibitors/)
- Enzyme: Steroid 11β-hydroxylase (CYP11B1)
- ATC code: V04CD01

✂**Steroid 11β-hydroxylase (CYP11B1)**Metyrapone

ⓘ The figure shows metyrapone itself bound to the heme of human CYP11B1 (an engineered mutant used for crystallisation).

**Target in 3D:** Steroid 11β-hydroxylase (CYP11B1). PDB structure 7E7F (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/7E7F) · Drag to rotate · pinch to zoom

## Mechanism of action

Metyrapone binds the heme iron of 11β-hydroxylase (CYP11B1), the mitochondrial enzyme that turns 11-deoxycortisol into cortisol in the adrenal cortex. Cortisol and corticosterone fall. With a normal pituitary, ACTH rises and drives more 11-deoxycortisol, which is measured in the test of pituitary reserve. The accumulating precursors have mineralocorticoid and androgen effects.

- Metyrapone binds the heme of 11β-hydroxylase (CYP11B1)
- 11-deoxycortisol is not converted to cortisol
- Cortisol falls; a normal pituitary raises ACTH
- 11-deoxycortisol accumulates and can be measured

## Pharmacokinetics

**Absorption**
Given by mouth as capsules

## Indications

- Test of pituitary ACTH reserve (metyrapone test)
- Control of severe cortisol excess in Cushing syndrome while the cause is treated [Cushing syndrome →](https://durgical.com/en/conditions/cushing-syndrome/)

## Adverse effects

### Common

- Dizziness and sedation
- Nausea and abdominal discomfort
- Headache
- Hirsutism and acne with longer use

### Serious (rare, important)

- Acute adrenal insufficiency
- Salt and water retention, high blood pressure and low potassium

## Contraindications

- Adrenal cortical insufficiency
- Hypersensitivity to metyrapone

## Key interactions

**Anticonvulsants, psychotropic drugs, hormone preparations, corticosteroids, antithyroid drugs and cyproheptadine**
Can distort the result of the metyrapone test

**Paracetamol (acetaminophen)**
Metyrapone inhibits its glucuronidation

## What is monitored

- Cortisol (and 11-deoxycortisol) levels
- Symptoms of adrenal insufficiency
- Blood pressure and potassium

## Administration and safety

- Given by mouth; drugs that distort the test are reviewed beforehand
- Before the test, the adrenal glands' ability to respond to ACTH is confirmed

## Nursing care

- Watch for weakness, dizziness, low blood pressure, nausea and vomiting (adrenal insufficiency)
- Warn about drowsiness and dizziness: no driving until it passes
- Time the blood samples exactly as the test protocol states

## Pregnancy and breastfeeding

It is the adrenal inhibitor that can be used in pregnant women with Cushing syndrome, with specialist follow-up.

## Memory aid

METyrapone METs the last step: 11-deoxycortisol piles up at the 11β-hydroxylase wall.

## Test yourself

Think of the answer, then tap the question to see it.

## In a metyrapone test, what result shows a normal pituitary reserve?

Cortisol falls while ACTH and 11-deoxycortisol rise, showing the pituitary responded to low cortisol.

## Why can metyrapone cause hypertension and hypokalaemia?

Precursors such as 11-deoxycorticosterone build up behind the block and act as mineralocorticoids.

## Which adrenal inhibitor can be used in pregnancy for Cushing syndrome?

Metyrapone.

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## Related drugs

- [Hydrocortisone](https://durgical.com/en/pharmacology/hydrocortisone/)

## Related conditions

- [Cushing syndrome](https://durgical.com/en/conditions/cushing-syndrome/)

[← Back to the class: Adrenal steroid synthesis inhibitors](https://durgical.com/en/pharmacology/classes/adrenal-steroid-synthesis-inhibitors/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Farmacología básica y clínica (Katzung), 16.ª ed., cap. 39 (McGraw Hill, 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=V04CD01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [Human CYP11B1 mutant in complex with metyrapone](https://www.rcsb.org/structure/7E7F) (RCSB Protein Data Bank, 2021).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/metyrapone/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/metyrapone/