Drug Levels and Effects:

Summary of Use during Lactation:

Evidence from one patient indicates that amounts of metyrapone and its active metabolite in breastmilk are very small and unlikely to adversely affect a breastfed infant. Exposure of the infant can be further minimized by avoiding nursing for 2 to 2.5 hours after each dose.

Drug Levels:

Maternal Levels.

A woman was taking metyrapone 250 mg orally 4 times daily during pregnancy and postpartum. At 1 week postpartum, milk samples were obtained before the midday dose and at 1.25, 2.25, 3.25, 4.24 and 5.25 hours after the dose. Samples were analyzed for metyrapone and its active metabolite racemic metyrapol. Peak milk concentrations of the drug and metabolite occur at 1.25 hours after the dose; by 2.25 hours after the dose, milk levels had dropped by about 75%. Half-lives in milk were 3.63 hours for metyrapone and 34 hours for metyrapol, respectively. The authors calculated that the combined dose a fully breastfed infant would receive is 9 mcg/kg daily or 0.1% of the weight-adjusted maternal dosage.[1]

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

Relevant published information was not found as of the revision date.

Possible Effects on Lactation:

Relevant published information was not found as of the revision date. Women taking metyrapone chronically for suppression of hypercorticism associated with Cushing's syndrome may have other hormonal abnormalities that might interfere with lactation.


1. Hotham NJ, Ilett KF, Hackett LP et al. Transfer of metyrapone and its metabolite, rac-metyrapol, into breast milk. J Hum Lact. 2009;25:451-4. PMID:19759353

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antimetabolites

  • Enzyme Inhibitors

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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