Buspirone

Limits on what this shows

• Null/negative findings: No study identified measuring mitochondrial parameters in normal (non-hepatocyte-toxicology) adult human tissue at standard clinical buspirone exposure; the 200 micromolar test concentration substantially exceeds buspirone's clinical plasma range (roughly 1-6 ng/mL, i.e., low nanomolar).
• At-risk subgroups: None established; the only context modeled is isolated hepatocyte/mitochondrial preparations at supratherapeutic concentration.

Regulatory status

Not addressed in FDA labeling; no mitochondrial-toxicity warning.

Population evidence

Dykens et al. 2008, Toxicological Sciences 103(2):335-345, in vitro isolated rat liver mitochondria, HepG2 hepatocyte cells, and human hepatocytes expressing CYP3A4, tested at 200 micromolar: buspirone showed "3.4-fold less inhibition of OXPHOS Complex I than nefazodone" and was reported to have "the least toxicity" of the three drugs tested; nefazodone was profoundly toxic with marked Complex I and IV inhibition, and trazodone showed intermediate effects with no Complex I inhibition. The retrievable summary of this study did not include a directly reported ATP-synthesis-rate figure for buspirone specifically (see the ATP production entry below for why this source is not carried into that entry).

Mechanism

Mild, concentration-dependent inhibition of mitochondrial Complex I of the electron transport chain, substantially less pronounced than the two comparator drugs; mechanistically adjacent to, but not the same measurement as, the oxidative-stress and gene-expression findings in the entry above.

Counter-evidence held on record

This is a reassuring comparative finding (least mitochondrial toxicity of the three drugs tested), not evidence of mitochondrial harm, and the concentration tested (200 micromolar) is far above buspirone's typical clinical plasma range. It should not be read as either a basis for concern or for CoQ10/mitochondrial-support supplementation, for which no dosing evidence exists in this drug's population.

Limits on what this shows

• Null/negative findings: SOD and catalase were not measured in the Abdel-Salam CCl4 study (only MDA, GSH, nitric oxide, and PON1 were reported), so that study cannot be used to corroborate the SOD/catalase direction seen in Freitas and El-Dessouki. No study identified measured oxidative stress markers in buspirone-treated patients or in non-challenged (healthy) animals; all positive findings come from toxin- or disease-challenged tissue.
• At-risk subgroups: None established in humans; all direct evidence is rodent or in vitro, and all used a co-administered toxic or disease challenge rather than buspirone alone.

Regulatory status

Not addressed in FDA labeling.

Population evidence

Freitas et al. 2010, Brain Research Bulletin, in vivo adult male Wistar rats, pilocarpine-induced seizure model, intraperitoneal buspirone pretreatment: reduced hippocampal lipid peroxidation by 60%, reduced nitrite content by 44%, increased SOD activity by 47%, and increased catalase activity by 40% versus pilocarpine-only controls, alongside suppression of behavioral seizures. Abdel-Salam et al. 2017, J Experimental and Clinical Toxicology, in vivo Sprague-Dawley rats (n=6/group), oral buspirone 10-30 mg/kg against carbon-tetrachloride (CCl4) hepatotoxicity over 7 days: at 30 mg/kg, buspirone reduced hepatic malondialdehyde (MDA) by 15.8%, restored glutathione (GSH) by 20.1%, reduced nitric oxide by 17.4%, and increased serum paraoxonase-1 (an antioxidant enzyme) by 43.9-53.5%, versus CCl4-alone controls, alongside reductions in ALT (19.5-34.3%), AST (24.2-31.4%), and ALP (21.7%). El-Dessouki et al. 2026, Frontiers in Pharmacology, in vivo male Wistar rats (n=8/group), oral buspirone 5-10 mg/kg against cyclophosphamide-induced nephrotoxicity over 11 days: at 10 mg/kg, buspirone reduced protein carbonyls by 51.9%, increased SOD activity by 186.0%, and increased HO-1 expression by 168.2% versus cyclophosphamide-alone controls (all p<0.01), alongside reductions in serum creatinine (45.6%) and BUN (41.5%). Althagafy et al. 2023, J Biochemical and Molecular Toxicology, in vivo rat methotrexate-induced hippocampal toxicity model: title and indexed record confirm buspirone "attenuated" toxicity via Nrf2/HO-1, PPAR-gamma, NF-kB/nNOS, and ROS/NLRP3/caspase-1 signaling (protective direction confirmed at the title/indexed level; the publisher blocked full-text retrieval with an HTTP 403 response during this review, so quantitative magnitudes are not independently verified here). Biswal et al. 2021, IOVS/ARVO annual meeting abstract, C57BL/6J mice (intraperitoneal buspirone 30 mg/kg x12 days) against sodium-iodate-induced retinal pigment epithelium (RPE) injury, plus paraquat-challenged human ARPE-19 cell culture: buspirone preserved outer nuclear layer thickness (88.0 vs 32.8 micrometers in vehicle controls, p<0.0001), preserved RPE tight-junction integrity, and increased expression of cytoprotective antioxidant genes including Nqo1, Cat, Gstm1, and the mitochondrial antioxidant gene Sod2.

Mechanism

Buspirone's 5-HT1A agonism and downstream Nrf2/HO-1 antioxidant-pathway activation are proposed across these studies as the mechanism for reduced oxidative stress in each toxin/disease model; not established as a baseline (non-challenged) antioxidant effect in normal tissue.

Counter-evidence held on record

This is a reverse-direction (protective) finding in toxin-challenged animal tissue, not evidence of oxidative stress caused by buspirone, and it does not establish an antioxidant benefit in ordinary human anxiety treatment. Do not use this entry to justify antioxidant supplementation on top of buspirone; no dosing evidence exists in this drug's human population for any of the compounds discussed (SOD, glutathione, or antioxidant-gene induction are endogenous responses, not supplements). See Overlap map: these five studies are independent experiments in different organ systems, but they converge on the same general pharmacological property (buspirone's antioxidant/Nrf2-inducing activity in challenged tissue) and should be read as one converging mechanistic story, not five unrelated clinical confirmations.

Limits on what this shows

• Why no grade: Both conditions for ungraded are met on the evidence actually retrieved: no Tier B or Tier C evidence was found to support even a yellow grade (the nearest candidate source explicitly excluded buspirone from its cohort), and no circulating consumer claim specific to buspirone and copper was found on the four sources checked. PMID 17604252 (Farooq, Haleem & Haleem 2007, a rat electrolyte study flagged in the prior review as unresolved and directly relevant to this drug) was successfully retrieved this revision and confirmed to address sodium and magnesium only, with no mention of copper; it does not change this entry's grade. Treated as a genuine evidence gap on the now-completed PubMed channel, with a disclosed tooling limitation on Europe PMC/Crossref/OpenAlex-search that a later revision should re-attempt.

Channels tried (this revision)

PubMed search-listing pages, four separately phrased queries, all successfully returned (not blocked this session, reachable with pacing between requests): "buspirone copper" (2 results, both irrelevant: an ion-selective-electrode analytical chemistry method using a copper-coated sensor to assay buspirone tablets, and an unrelated antiemetic-receptor study); buspirone AND "trace element" (0 results); buspirone AND "trace metal" (0 results). DailyMed label search for "buspirone iron copper" (0 matches). Europe PMC REST API and OpenAlex's works-search endpoint were rate-limited (HTTP 429) on every attempt this session and could not be used to independently corroborate the PubMed negative; OpenAlex's per-record lookup endpoint (which did work reliably for named PMIDs elsewhere in this revision) has no relevant PMID to look up here, since no candidate source was found. Also re-reviewed: Schlegel-Zawadzka & Nowak 2000 (imipramine, citalopram, electroconvulsive shock only, buspirone not in cohort, fails the cohort test). Consumer sources re-checked: Drugs.com (buspar.html), Suzy Cohen site search, and two psychiatric-drug depletion charts - none list buspirone.

Outcome

Clean negative across four differently phrased PubMed queries this revision, a more thorough sweep than the prior review's two WebSearch queries. Europe PMC, Crossref, and OpenAlex's works-search remain tooling-blocked (HTTP 429) rather than clean negatives on this specific category, so a later revision should still re-check those three channels directly, though the PubMed sweep now meets the Step 4 thoroughness bar (multiple phrasings, genuinely completed rather than a single blocked attempt).

Limits on what this shows

• Why no grade: Both conditions for ungraded are met on the evidence actually retrieved: no Tier B or Tier C evidence exists to support even a yellow grade, and no circulating claim specific to buspirone and iron was found on the sources checked. PMID 17604252 (the previously blocked rat electrolyte study, see Copper entry above) was retrieved this revision and confirmed to address sodium and magnesium only, with no mention of iron; it does not change this entry's grade. Treated as a genuine evidence gap on the completed PubMed queries, with a disclosed incomplete query and a disclosed tooling limitation on Europe PMC/OpenAlex-search flagged for a later revision.

Channels tried (this revision)

PubMed search-listing pages, three separately phrased queries, all successfully returned: "buspirone iron" (2 results, both irrelevant: a 1994 akathisia review mentioning iron status only as a general pathophysiology concept unrelated to buspirone, and a 2016 drug-metabolism-simulation paper using buspirone as one of several test compounds with no iron content); buspirone AND "trace metal" (0 results); buspirone AND "iron deficiency" (0 results). A fourth query combining buspirone with ferritin/transferrin/"iron status" using OR-grouping syntax returned a mis-parsed, non-buspirone result set on first attempt and was not successfully re-run before rate-limiting; this is disclosed as incomplete rather than folded into the clean-negative count. DailyMed label search for "buspirone iron copper" (0 matches). Europe PMC REST API and OpenAlex's works-search endpoint were rate-limited (HTTP 429) throughout this session.

Outcome

Clean negative across the three completed, correctly-parsed PubMed queries. The ferritin/transferrin/"iron status" combined query is disclosed as an incomplete attempt (a parsing issue, not a tooling block) that a later revision should re-run with corrected query syntax before treating iron as fully closed. Europe PMC and OpenAlex-search remain tooling-blocked rather than clean negatives.

Limits on what this shows

• Null/negative findings: Alpha-diversity was not significantly changed by buspirone in either direction in this study, a partial null worth preserving alongside the beta-diversity and taxa-level findings. No study was located examining buspirone's effect on a healthy, non-stressed gut microbiome, so a disruptive effect in ordinary use cannot be ruled out, only that none was found.
• At-risk subgroups: None established in humans; all evidence is murine and confined to a stress/infection disease model.

Regulatory status

Not addressed in FDA labeling.

Population evidence

Kim et al. 2021, Scientific Reports 11:5087, in vivo male C57BL/6N mice (n=6/group), buspirone 5 mg/kg/day oral gavage or 1 mg/kg/day intraperitoneal for 5 days, against immobilization-stress (IS) or E. coli K1 (EC)-induced anxiety/depression and colitis: buspirone "partially restored IS- or EC-induced gut microbiota perturbation such as beta-diversity to those of normal control mice" (alpha-diversity was not significantly affected either way); reduced stress-associated Proteobacteria overgrowth; increased Bacteroidetes, Verrucomicrobiota, and the beneficial genera Bacteroides and Roseburia; and alleviated stress-induced colitis by suppressing myeloperoxidase activity, TNF-alpha, IL-1beta, IL-6, and NF-kB activation in colon tissue.

Mechanism

Not fully characterized; serotonin signaling has documented roles in gut motility, mucosal immune function, and bacterial gene expression, offering biological plausibility for a restorative effect specifically in a stressed or inflamed gut rather than a uniform effect in a normal one.

Counter-evidence held on record

All evidence is in mice and in a stress/colitis disease model; no human gut microbiome data exist for buspirone. This should not be generalized as either a uniform protective or a uniform harm claim in ordinary human use, and does not support a probiotic or microbiome-targeted supplementation recommendation.

Limits on what this shows

• Null/negative findings: Argyropoulou et al. 1993 (the Tier A human COPD crossover trial discussed in the empty-orange-tier note above) measured arterial blood gases and ventilatory drive directly in humans and found no significant change with buspirone; that trial did not measure hematocrit or red-cell indices, so it neither corroborates nor contradicts this rat finding, and the two are not the same endpoint. This session's tooling could not retrieve the verbatim published abstract or full text of the Alam et al. 2021 paper (PubMed's individual article page returned only boilerplate on every attempt, and no PMC full text exists for this PMID); the summary above rests on an AI-reconstructed abstract from OpenAlex's indexed inverted-index text, not a direct read of the original, and exact percentages or p-values could not be confirmed.
• At-risk subgroups: None established in humans; the only direct evidence is a single rat toxicology study, at a dose (10 mg/kg/day) above typical human clinical exposure on a body-weight basis.

Regulatory status

Not addressed in FDA labeling; no hematologic monitoring requirement.

Population evidence

Alam N, Ikram R, Naeem S, Khan SS, Siddiqui T, Khatoon H, Kashif SS. 2021, Pakistan Journal of Pharmaceutical Sciences, in vivo male Wistar rats (n=40, 4 groups of 10): saline control, methylphenidate 2 mg/kg/day, buspirone 10 mg/kg/day, and methylphenidate+buspirone combined, dosed for six weeks. Per the retrievable (OpenAlex-reconstructed) abstract: hematocrit, MCV, MCH, and MCHC were decreased in all treated groups, including the buspirone-alone arm, relative to saline controls; RBC and WBC counts were also decreased in treated groups. Hemoglobin and cholesterol increases were reported specifically for the combination arm, not stated for buspirone alone. Serum creatinine decreased across all treated groups (a renal, not hematologic, finding, noted here only for completeness).

Mechanism

Not established. No named mechanism connects 5-HT1A partial agonism to reduced erythropoiesis or red-cell indices; the study is a general toxicology/safety screen for the methylphenidate-buspirone combination, not a mechanistic hematology study.

Counter-evidence held on record

This is a single Tier B animal study with an abstract that could only be reconstructed rather than read verbatim, not confirmed human hematologic data, and it should not be read as evidence of anemia or reduced oxygen-carrying capacity in patients taking buspirone. It does not support iron, B12, or other hematinic supplementation, for which no dosing evidence exists in this drug's population; a later revision should prioritize obtaining the verbatim full text to confirm magnitudes and statistical significance before this entry is strengthened further.

Limits on what this shows

• Why no grade: Both conditions for ungraded are met on the evidence actually retrieved: the one source with an ATP-specific endpoint could not be read for its actual result (direction and magnitude both unknown), so it cannot support even a yellow grade under this protocol's citation rule (do not cite a source for a finding you did not actually read), and no circulating "low energy" or ATP-depletion claim specific to buspirone was found (see consumer sources checked under Copper/Iron above). The Mitochondrial burden entry above is not treated as a substitute grade for this category, per Hard Rule 7 (the two must remain independent entries), and its Complex I finding is not carried in here because it is a different endpoint than ATP content.

Channels tried (this revision)

PubMed search-listing pages, two queries: buspirone AND "adenosine triphosphate" (2 results: Dykens et al. 2008, PMID 18344530, and an unrelated 1989 adenylate-cyclase receptor-pharmacology paper with no ATP-synthesis content); buspirone AND "oxidative phosphorylation" query attempted but not completed before rate-limiting. Unpaywall lookup for Dykens 2008's DOI (10.1093/toxsci/kfn056, confirmed) returned an open-access PDF location at Oxford University Press. That PDF was fetched directly and the figure caption confirms an ATP-content assay was run for buspirone (200 micromolar, HepG2 cells, 24h exposure, n=3 experiments, expressed as percent of vehicle-treated controls), but the numeric value itself is presented only as an image-based bar/line figure that this session's PDF-to-text tooling could not extract, on two separate fetch attempts. OpenAlex's per-record lookup of the same PMID returned only the published abstract text, which itself does not restate the ATP percentage (confirming the omission is in the source's abstract, not a retrieval failure on that channel specifically).

Outcome

Clean negative confirmed on the completed PubMed ATP-specific query: Dykens 2008 remains the only buspirone-specific source touching this endpoint at all. The source itself is now fully located and its relevant endpoint confirmed to exist, but the specific figure value remains inaccessible through this session's available tooling (image-embedded data, not a text/API block). A later revision with OCR or figure-extraction capability, or a supplementary-data file for this article, should be tried before this is treated as permanently inaccessible.