Metyrapone

Limits on what this shows

• Key negative/null findings: An unrelated in vitro study in human neuroblastoma cells (250 µM metyrapone) described it as "an inhibitor of cytochrome oxidases" in the context of bilirubin-oxidation research, but found metyrapone alone "did not influence cell viability" and did not worsen bilirubin-induced cytotoxicity (2014, Mol Genet Metab Rep, PMID 27896088). This is off-target, non-adrenal, in vitro evidence with a null functional outcome. See Overlap map (shared with the ATP production entry).
• At-risk subgroups: None identified for generalized mitochondrial effects; the intended, tissue-specific effect applies to anyone taking the drug for its labeled purpose.
• Counter-evidence on record: The 2014 neuroblastoma study is a direct counter-finding against generalized mitochondrial/cytotoxic harm at the concentration tested.

Regulatory status

Label describes the mechanism as inhibition of 11-beta-hydroxylation; it does not use mitochondrial-toxicity language.

Population evidence

Foundational biochemistry: metyrapone's site of action was mapped directly to adrenal-mitochondrial preparations from rat, ox, sheep, and human tissue (Sharma & Purohit 1974, PMID 4152546; Sheppard & Swann 1973, PMID 4729811; Perry & Purohit 1976, "Dual sites of inhibition by metyrapone of human adrenal steroidogenesis," PMID 1262443). These are Tier B mechanistic/biochemical studies, not clinical-outcome trials.

Mechanism

Named and specific: competitive inhibition of the heme-thiolate active site of CYP11B1 (and, at the human dual-inhibition site, CYP11B2), confined to steroidogenic mitochondria of the adrenal cortex.

Counter-evidence held on record

Per Hard Rule 2, this entry exists to clarify mechanism, not to claim a mitochondrial-nutrient deficiency: the adrenal-mitochondrial enzyme inhibition is the drug's intended pharmacologic effect, not evidence of systemic mitochondrial harm or a CoQ10/B-vitamin cofactor depletion, for which no evidence was found.

Limits on what this shows

• Key negative/null findings: In the combined nicotine-plus-stress model, metyrapone provided only partial protection, it did not fully normalize oxidative markers, which bounds the magnitude of the protective effect.
• At-risk subgroups: Not applicable; these are rodent CNS-stress models, not a human at-risk population.
• Counter-evidence on record: No human data located. Direct access to the full PubMed abstract pages for both PMIDs was blocked by a bot-verification challenge; the summaries above were reconstructed via the OpenAlex API's abstract index rather than the original journal text, a disclosed access limitation.

Regulatory status

Not addressed in the label.

Population evidence

Two Tier B rat studies, both naming metyrapone specifically: chronic hypobaric hypoxia memory-impairment model, metyrapone reduced lipid peroxidation (MDA) and reactive oxygen species and improved hippocampal outcomes (2011, Behav Brain Res, PMID 22137888); chronic unpredictable mild stress plus nicotine model, metyrapone reversed nicotine-associated pro-oxidative changes, though it did not fully reverse combined stress-plus-nicotine damage (2017, Mol Neurobiol, PMID 28484990, dose 50 mg/kg).

Mechanism

Named: reduced glucocorticoid signaling lowers glucocorticoid-mediated oxidative damage; both studies frame this as corticosterone, not metyrapone, driving the oxidative burden.

Counter-evidence held on record

This is animal, mechanistic evidence only, and it runs in the protective direction. It must never be read as a human claim that metyrapone "reduces oxidative stress" or as grounds for antioxidant supplementation; it only clarifies that excess cortisol/corticosterone, not this drug, is the oxidative driver in these models.

Limits on what this shows

• Key negative/null findings: No metyrapone-specific iron, ferritin, transferrin, or hepcidin measurement was found in either direction.
• At-risk subgroups: Not established.
• Counter-evidence on record: The labeled hematologic adverse reaction "anemia" (see Oxygen delivery/utilization entry) is not attributable to iron status in any source reviewed; the one identified anemia case was attributed to a paraneoplastic inflammatory process, not iron handling.

Regulatory status

Not addressed in the label.

Population evidence

Class-level only: a 2026 review on iron deficiency in endocrine disease discusses cortisol among several hormonal pathways that intersect with hepcidin and iron handling (La Vignera & Condorelli, PMID 42792685), and separate stress-physiology literature (e.g. Augustine et al. 2016, PMID 28139536, on allostatic load and iron/hepcidin in adolescents) links cortisol-axis activation to iron parameters. None of these studied metyrapone; this is Tier C class extrapolation and is capped at yellow accordingly.

Mechanism

Plausible only: if cortisol modulates hepcidin, then pharmacologically lowering cortisol could in principle shift iron handling, but direction (higher or lower iron availability) is not established even at the class level for this specific pathway.

Counter-evidence held on record

Kept independent from Copper and from the Oxygen delivery/utilization entry per Hard Rule 7. No iron supplementation is implied by this entry; iron status should be assessed on clinical grounds unrelated to metyrapone specifically.

Limits on what this shows

• Why no grade: Both conditions for UNGRADED are met: (1) no Tier B or Tier C evidence exists to support even a yellow grade, the only copper-adjacent hits were radiochemistry papers using Cu(I)-assisted halogen exchange to radiolabel a metyrapone derivative for imaging purposes (PMID 7767321, PMID 8998470), which are chemistry-synthesis methods papers with no bearing on copper nutrient status, plus one unrelated finding that a copper-catalyzed microsomal chemiluminescence reaction was "not inhibited by metyrapone" (PMID 2840858, 1988), a null finding that if anything argues against a copper-pathway interaction; (2) no consumer or practitioner claim about metyrapone and copper was located to rebut as white.

Search channels tried

PubMed search-listing pages (multiple phrasings: "metyrapone copper," "metyrapone ceruloplasmin"), OpenAlex works search. WebSearch was unavailable (session budget exhausted before this review began). Europe PMC's REST API and the Semantic Scholar API returned persistent HTTP 429 responses across repeated attempts and could not be used for this category; a future revision should re-check those two channels specifically.

Limits on what this shows

• Key negative/null findings: None specific to metyrapone found; broader literature on the HPA axis and the gut microbiome (Rusch et al. 2023, PMID 37404311; Tofani et al. 2025, PMID 39504963) is class-level and not stratified to this drug, cited here only as background context, not as supporting evidence for a metyrapone-specific claim.
• At-risk subgroups: Not established for humans; the supporting data are a single rodent trauma model.
• Counter-evidence on record: No microbiome composition, diversity, or 16S/shotgun-sequencing data for metyrapone in any species were located.

Regulatory status

Not addressed in the label.

Population evidence

Rats given alcohol plus burn injury, then metyrapone 25 mg/kg: metyrapone prevented corticosterone-driven suppression of mesenteric lymph node T-cell proliferation and IL-2 production, and was associated with reduced bacterial translocation to mesenteric lymph nodes (Zahs et al., Am J Physiol Regul Integr Comp Physiol, 2005, PMID 15718389).

Mechanism

Named: corticosterone suppresses gut-associated lymphoid tissue via p38/ERK pathway inhibition, promoting bacterial translocation after injury; removing corticosterone (via metyrapone) reverses this specific immune-mediated barrier failure.

Counter-evidence held on record

This is narrow, injury-model, barrier-function evidence, not a general statement about gut microbiome health on metyrapone. No probiotic or fiber recommendation is implied.

Limits on what this shows

• Key negative/null findings: A 1980 study of pituitary-adrenal axis function in sickle cell disease patients given metyrapone (PMID 7011001) reports impaired 11-deoxycortisol response as expected, with no mention of metyrapone-induced hematologic toxicity in that cohort.
• At-risk subgroups: Not defined in available sources; the one case involved a patient with an underlying malignancy and systemic inflammation, a strong confounder.
• Counter-evidence on record: Confounding by indication is presumed here per Hard Rule 6: the identified anemia case had an alternative, better-supported cause (paraneoplastic IL-6-driven inflammatory anemia), and the PROMPT trial abstract does not list anemia among its leading adverse events.

Regulatory status

Label lists hematologic adverse reactions: leukopenia, anemia, thrombocytopenia, sourced from clinical trials and postmarketing reports, without frequency data.

Population evidence

Case report of a patient on metyrapone 1,000 mg/day for ectopic-ACTH pheochromocytoma who developed anemia; the authors attributed it to "hyper-IL-6emia... inflammatory hematopoietic disorder" from the underlying tumor rather than to metyrapone itself (PMID 39956584, 2025).

Mechanism

Not established for metyrapone specifically. No hemolysis, marrow-suppression, or nutrient-mediated mechanism is named in the label.

Counter-evidence held on record

Anemia is a clinical outcome, not evidence of iron, B12, or copper deficiency; see the Iron entry, which is graded independently and lower, per Hard Rule 2. A patient developing anemia on metyrapone should be worked up for the underlying disease and for its own hematinic status by a clinician, not assumed to be a mineral-depletion effect of the drug.

Limits on what this shows

• Key negative/null findings: Both available direct measurements (mitochondrial O2 consumption unchanged; cell viability unchanged) are null results, and are recorded here as the most informative findings in this entry, not omitted.
• At-risk subgroups: None identified.
• Counter-evidence on record: See key negative findings; no positive human or animal signal of impaired ATP production was located after a genuine multi-channel search (PubMed listing pages, OpenAlex).

Regulatory status

Not addressed in the label.

Population evidence

Rat study measuring systemic and cerebral (hippocampal) energy metabolism after metyrapone: blood lactate rose modestly and mild hypothermia occurred, but mitochondrial oxygen-consumption rates and phosphorylated AMPK/mTOR signaling were unchanged between groups, and the authors framed the pattern as consistent with metyrapone's known neuroprotective profile rather than an energy deficit (Drouet et al. 2012, Eur J Pharmacol, PMID 22387859).

Mechanism

No mechanism for a direct ATP-synthesis effect is established; the cytochrome-oxidase-inhibitor label from the neuroblastoma study (PMID 27896088, 250 µM, in vitro) is the only structural link to the electron transport chain, and it produced no measurable functional deficit.

Counter-evidence held on record

Graded yellow only because Tier B evidence exists to discuss, not because a deficit was found; the direction of the available data is null-to-reassuring, and no supplement or dose is implied.