Trazodone

Limits on what this shows

• Key negative/null findings: Albert-Gasco H et al., "Trazodone rescues dysregulated synaptic and mitochondrial nascent proteomes in prion neurodegeneration," Brain, PMID 37703312 (2024) - found trazodone protective for mitochondrial proteome dysregulation in a neurodegeneration model, the opposite direction from a burden finding. This is an important counter-signal and is why this entry is not framed as one-directional harm.
• At-risk subgroups: None established at therapeutic human exposures; all quantitative effects described above were observed at concentrations well above typical clinical plasma levels or in isolated/ex vivo systems.
• Counter-evidence on record: See Albert-Gasco 2024 above; also, no complex II-linked respiration effect was found for trazodone in either study.

Regulatory status

Not addressed in the FDA label; this entry rests entirely on Tier B mechanistic literature.

Population evidence

Dykens JA et al., "In vitro assessment of mitochondrial dysfunction and cytotoxicity of nefazodone, trazodone, and buspirone," Toxicol Sci 2008;103(2):335-345 (DOI 10.1093/toxsci/kfn056): in isolated rat liver mitochondria, trazodone showed no inhibition of OXPHOS Complex I (unlike nefazodone); in HepG2/human hepatocyte cultures, both nefazodone and trazodone collapsed mitochondrial membrane potential after 24-hour exposure, with trazodone's effects described as "relatively modest" compared to nefazodone. Ľupták M, Fišar Z, Hroudová J, "Different Effects of SSRIs, Bupropion, and Trazodone on Mitochondrial Functions and Monoamine Oxidase Isoform Activity," Antioxidants 2023;12(6):1208 (DOI 10.3390/antiox12061208): in pig-brain isolated mitochondria, trazodone at 50-100 µmol/L (supratherapeutic) reduced complex I-linked respiration (ranked second after escitalopram among six antidepressants tested) and reduced complex IV activity to roughly 22% of control at the top concentration, without affecting complex II-linked respiration.

Mechanism

Partial inhibition of electron transport chain complexes (I and IV) and loss of mitochondrial membrane potential at high, non-therapeutic concentrations; no effect on Complex I demonstrated at the concentrations used in the isolated rat-liver-mitochondria arm of the Dykens study.

Counter-evidence held on record

All quantitative mitochondrial effects described here were observed at supratherapeutic concentrations in isolated mitochondria, cell culture, or ex vivo hepatocytes, not in living patients at approved doses. This is mechanistic plausibility, not a demonstrated clinical deficit, and should never be presented to a consumer as an established effect.

Limits on what this shows

• Key negative/null findings: Nesterowicz 2023 itself is the null/counter-finding for a simple "trazodone is an antioxidant" claim: its radical-scavenging activity was consistently far weaker than reference antioxidant compounds, and it actively worsened glycation markers rather than protecting against them.
• At-risk subgroups: None established in humans at therapeutic dosing; the rat studies used repeated or toxicological dosing paradigms specifically designed to elicit toxicity.
• Counter-evidence on record: Protective co-agents (L-carnitine, sage/Salvia officinalis extract, melatonin, taurine) were shown in the same literature to mitigate trazodone-associated oxidative damage in rat models, which is itself evidence that the underlying effect is real but modest and modifiable, not evidence of no effect.

Regulatory status

Not addressed in the FDA label.

Population evidence

Nesterowicz M et al., "Biochemical and Biophysical in Vitro Studies and Systematic Literature Review on the Antioxidant and Antiglycation Activities of Trazodone," DOI 10.33594/000000617 (2023): in cell-free spectrophotometric assays, trazodone showed weak radical-scavenging capacity (41% hydroxyl-radical inhibition, 1% nitric-oxide inhibition, 2% DPPH inhibition, 6% hydrogen-peroxide inhibition, versus 67-94% for reference antioxidants aminoguanidine/N-acetylcysteine) and modest ferrous-ion chelation, but in a bovine-serum-albumin glycation model it significantly increased glycation/oxidation markers (kynurenine +244%, N-formylkynurenine +669%, dityrosine +136%, advanced glycation end products +348%) rather than decreasing them. Khedr NF, Werida RH, PMID 34637798 (2022) and Ilgın S et al., PMID 30151072 (2018), both report induced testicular oxidative stress in rats given trazodone at toxicological doses; Khedr NF, El-Feky OA, Werida RH, PMID 35781619 (2022) reports trazodone-induced rat cardiotoxicity mediated via oxidative stress and autophagy. Title/PMID-level access only for the three PubMed-listed animal studies (see Sources).

Mechanism

The in vitro data indicate trazodone is a weak direct radical scavenger but a pro-glycation agent on protein; the animal toxicology data show oxidative-stress markers (and protective effects of co-administered L-carnitine or sage extract) in reproductive and cardiac tissue at doses used to model toxicity, not standard therapeutic dosing.

Counter-evidence held on record

Do not present trazodone as either a protective antioxidant or a clean pro-oxidant; the honest reading is mixed and dose/model-dependent, with the human-relevant toxicological studies conducted in rats at doses designed to produce toxicity, not at standard therapeutic exposures.

Limits on what this shows

• Why no grade: Both conditions for ungraded are met: no Tier B or C evidence exists to support even a yellow grade, and no circulating claim exists to rebut as white. A PubMed search for "trazodone copper" returned only articles about ceruloplasmin/copper metabolism in general, with no trazodone content at all; a Crossref bibliographic search for "trazodone copper ceruloplasmin metabolism" returned the same generic ceruloplasmin literature with zero trazodone overlap. No copper-related claim about trazodone appeared in the label, in any PubMed or Crossref result, or in the depletion-style claims (CoQ10, B12, folate, magnesium, melatonin) tested elsewhere in this dossier.

Tooling disclosure

PubMed's individual per-article pages and Europe PMC's REST API were intermittently blocked (bot-verification challenge or proxy rate-limiting) during this review; the PubMed search-listing page and the Crossref API, both used for this category, were accessible and returned genuine zero-overlap results rather than errors, so this is treated as a real literature gap rather than a pure tooling failure. General consumer/marketing search engines (Google, Bing, DuckDuckGo) were robots-blocked all session, so a fringe consumer claim circulating outside the channels checked here cannot be fully ruled out.

Limits on what this shows

• Why no grade: Both conditions for ungraded are met. A PubMed search for "trazodone iron" returned only pediatric sleep-disorder reviews that discuss iron supplementation (for restless-legs/periodic-limb-movement-associated insomnia) and trazodone as two separate, unrelated interventions in the same review article, plus an unrelated analytical-chemistry paper using ferric chloride as a colorimetric reagent to assay trazodone in the lab, not a biological iron interaction. No study measuring iron status, ferritin, or iron absorption in trazodone-treated patients or animals was found. No circulating consumer claim linking trazodone to iron was encountered in the claims specifically tested in this review.

Tooling disclosure

Same channel disclosure as Copper above: PubMed search-listing and Crossref were functional for this query and returned genuine non-overlapping results; general web search engines were blocked throughout the session by robots.txt, so this gap should be re-checked with broader consumer-claim tooling in a future revision.

Limits on what this shows

• Key negative/null findings: None specific to trazodone are available, precisely because no drug-specific study exists.
• At-risk subgroups: Cannot be specified without drug-specific data.
• Counter-evidence on record: This is explicitly labeled class extrapolation per Step 4/7 of the governing protocol: the class member with real data (fluoxetine, an SSRI) is pharmacologically distinct from trazodone (a SARI with dominant 5-HT2A antagonism), so the extrapolation is weaker than a same-subclass comparison would be.

Regulatory status

Not addressed in the FDA label.

Population evidence

A direct PubMed search for trazodone and gut microbiome/microbiota returned zero results. Class-level (Tier C) evidence exists for other serotonergic antidepressants: Fung TC et al., "Intestinal serotonin and fluoxetine exposure modulate bacterial colonization in the gut," PMID 31477894 (2019), found fluoxetine altered gut bacterial colonization (including reduced Turicibacter sanguinis) via intestinal serotonin signaling in mice; Zhang et al., PMID 33602895 (2021), and Dong et al., PMID 37537583 (2023), report fluoxetine and amitriptyline altering gut microbiota composition in rodent stress models. Trazodone was not in any of these cohorts.

Mechanism

Plausible but unconfirmed for trazodone: the gut's enterochromaffin cells and 5-HT3/5-HT4 receptor signaling regulate motility and the luminal environment that shapes microbiota composition, and trazodone is a serotonin-receptor antagonist and weak reuptake inhibitor, so a mechanistic link is biologically plausible even though its specific receptor profile (5-HT2A antagonism-dominant) differs from the SSRIs actually studied.

Counter-evidence held on record

This entry must not be presented to a reader as "trazodone disrupts your gut microbiome" - it is a plausibility flag drawn from a different (though related) drug class, not a trazodone-specific finding.

Limits on what this shows

• Key negative/null findings: No leukopenia, neutropenia, agranulocytosis, or thrombocytopenia is listed for trazodone in the label's adverse-reaction data, unlike some other psychotropics.
• At-risk subgroups: Label separately cautions using trazodone in men with sickle cell anemia, multiple myeloma, or leukemia because of priapism risk - a different mechanism (alpha-1 adrenergic antagonism), not the hemolytic-anemia signal, but worth distinguishing for the same at-risk hematologic populations.
• Counter-evidence on record: Postmarketing reports lack a denominator and causality is not established by spontaneous-report surveillance alone; this bounds the entry to orange rather than red.

Regulatory status

FDA label, postmarketing experience: "hemolytic anemia, leukocytosis" listed under Blood and Lymphatic System Disorders. No hematologic abnormality is listed in the controlled-trial adverse-reaction tables, marking this as a rare, spontaneously-reported signal rather than a common finding.

Population evidence

Perry PJ et al., "A report of trazodone-associated laboratory abnormalities," Ther Drug Monit 1990;12(6):517-519 (DOI 10.1097/00007691-199011000-00001) - examined hematocrit, hemoglobin, and red blood cell count changes during a comparative antidepressant trial that included trazodone. Bibliographic record confirmed via Crossref; full abstract text was not independently accessible during this review (see Sources).

Mechanism

Not established for the hemolytic-anemia signal specifically; no drug-specific hemolytic mechanism (e.g., G6PD-related, immune-mediated) is named in the label.

Counter-evidence held on record

This is a rare postmarketing signal, not an established or dose-dependent effect. Do not frame this as "trazodone causes anemia" for the general patient population; frame it as a rare reported event warranting routine clinical awareness, not supplementation.

Limits on what this shows

• Key negative/null findings: No effect on complex II-linked respiration was found for trazodone in the Ľupták 2023 study, and no Complex I inhibition was found for trazodone in the isolated rat-liver-mitochondria arm of the Dykens 2008 study.
• At-risk subgroups: None established at therapeutic human exposures.
• Counter-evidence on record: Both source studies frame their findings as concentration-dependent and note that the effects observed at 50-100 µmol/L exceed typical therapeutic plasma concentrations of trazodone.

Regulatory status

Not addressed in the FDA label.

Population evidence

Ľupták, Fišar, Hroudová, Antioxidants 2023;12(6):1208 (DOI 10.3390/antiox12061208) measured ATP alongside electron transport chain complex I-IV activity and respiratory rate in pig-brain isolated mitochondria exposed to trazodone at 50 and 100 µmol/L; complex I-linked respiration was reduced by escitalopram >> trazodone >> sertraline, i.e., trazodone's effect was intermediate and smaller than the SSRI comparator. Dykens JA et al., Toxicol Sci 2008;103(2):335-345 measured ATP content directly in HepG2 cells alongside the membrane-potential and OXPHOS findings reported under Mitochondrial burden, with trazodone's effects described as modest relative to nefazodone.

Mechanism

Partial ETC complex I and IV inhibition at supratherapeutic concentrations reduces oxidative-phosphorylation-linked ATP synthesis; this is the same underlying assay and mechanism reported under Mitochondrial burden (see Overlap map).

Counter-evidence held on record

This entry and Mitochondrial burden are not independent confirmations of each other; they report different endpoints (ATP content/respiration vs. membrane potential/complex activity) measured in the same experiments. See the Overlap map.