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Metapirone: Full Drug Profile

Medically reviewed by Min Clinic Staff | Updated: January 2026

Metapirone - General Information

An inhibitor of the enzyme steroid 11-beta-monooxygenase. It is used as a test of the feedback hypothalamic-pituitary mechanism in the diagnosis of cushing syndrome. [PubChem]

 

Pharmacology of Metapirone

Metopirone is an inhibitor of endogenous adrenal corticosteroid synthesis.

 

Metapirone for patients

 

Metapirone Interactions

Drugs affecting pituitary or adrenocortical function, including all corticosteroid therapy, must be discontinued prior to and during testing with Metopirone.

The metabolism of Metopirone is accelerated by phenytoin; therefore, results of the test may be inaccurate in patients taking phenytoin within two weeks before. Asubnormal response may occur in patients on estrogen therapy.

Metopirone inhibits the glucuronidation of acetaminophen and could possibly potentiate acetaminophen toxicity.

 

Metapirone Contraindications

Metopirone is contraindicated in patients with adrenal cortical insufficiency, or hypersensitivity to Metopirone or to any of its excipients.

 

Additional information about Metapirone

Metapirone Indication

Used as a diagnostic drug for testing hypothalamic-pituitary ACTH function.

Mechanism Of Action
The pharmacological effect of Metopirone is to reduce cortisol and corticosterone production by inhibiting the 11-ß-hydroxylation reaction in the adrenal cortex. Removal of the strong inhibitory feedback mechanism exerted by cortisol results in an increase in adrenocorticotropic hormone (ACTH) production by the pituitary. With continued blockade of the enzymatic steps leading to production of cortisol and corticosterone, there is a marked increase in adrenocortical secretion of their immediate precursors, 11-desoxycortisol and desoxycorticosterone, which are weak suppressors of ACTH release, and a corresponding elevation of these steroids in the plasma and of their metabolites in the urine. These metabolites are readily determined by measuring urinary 17-hydroxycorticosteroids (17-OHCS) or 17-ketogenic steroids (17-KGS). Because of these actions, metopirone is used as a diagnostic test, with urinary 17-OHCS measured as an index of pituitary ACTH responsiveness. Metopirone may also suppress biosynthesis of aldosterone, resulting in a mild natriuresis.
Generic Name
Metyrapone
Synonyms
Methapyrapone; Mepyrapone; Methbipyranone; Methopirapone; Methopyrapone; Methopyrinine; Methopyrone; Metyrapon; Metroprione
Drug Category
Antimetabolites; Enzyme Inhibitors
Drug Type
Small Molecule; Approved
Other Brand Names containing Metyrapone
Metapirone; Metapyron; Metapyrone; Metopiron; Metopyrone; Metopirone;
Absorption
Absorbed rapidly and well when administered orally. Peak plasma concentrations are usually reached 1 hour after administration.
Toxicity (Overdose)
Oral LD50 in rats is 521 mg/kg. One case has been recorded in which a 6-year-old girl died after two doses of Metopirone, 2 g. Symptoms of overdose include cardiac arrhythmias, hypotension, dehydration, anxiety, confusion, weakness, impairment of consciousness, nausea, vomiting, epigastric pain, and diarrhea.
Biotransformation
Hepatic. The major biotransformation is reduction of the ketone to metyrapol, an active alcohol metabolite. Metyrapone and metyrapol are both conjugated with glucuronide.
Half Life
1.9 ±0.7 hours.
Dosage Forms of Metapirone
Capsule Oral
Chemical IUPAC Name
2-methyl-1,2-di(pyridin-3-yl)propan-1-one
Chemical Formula
C14H14N2O
Organisms Affected
Humans and other mammals