Memantine

Limits on what this shows

• Key negative/null findings: McAllister J et al. (2008, PMID 18053965), same study as cited under Oxidative stress, measured Complex I and Complex IV electron transport chain activity, cytochrome oxidase protein, mitochondrial DNA levels, calcium levels, and oxygen consumption in human NT2 cells: Complex I activity was enhanced at high concentrations (60 uM) while Complex IV Vmax activity was reduced at high concentrations, a genuinely mixed, non-uniform result. The authors concluded memantine affects mitochondria in ways largely independent of NMDA channel antagonism, with both protective and harmful consequences depending on exposure.
• At-risk subgroups: Not established in humans; all direct evidence is preclinical (animal, cell line, or patient-derived iPSC neurons in vitro).
• Counter-evidence on record: The McAllister 2008 mixed-direction Complex I/IV finding above is the only source in this review reporting anything other than a protective direction; three of four other sources are unanimous in reporting protective/mitophagy-enhancing effects.

Regulatory status

Not addressed in the FDA label.

Population evidence

de Wet S et al. (2023, Cells 12(13):1726, PMID 37443760, DOI 10.3390/cells12131726): in GT1-7 murine hypothalamic neurons, memantine at 50 uM and 100 uM maintained mitochondrial network volume after CCCP-induced injury; the low concentration induced mitophagy specifically (increased automitosomes/automitolysosomes), while the high concentration induced macroautophagy without triggering mitophagy, a concentration-dependent divergence in mechanism rather than in overall protective direction. Hirano K et al. (2019, Biochem Biophys Res Commun 518(1):161-170, DOI 10.1016/j.bbrc.2019.08.025): across HeLa, SH-SY5Y, and iPSC-derived neurons from Huntington's and Parkinson's disease patients, memantine (10 uM, 24h) increased LC3-II in a dose- and time-dependent manner, upregulated autophagic flux, decreased huntingtin aggregates, and enhanced clearance of damaged mitochondrial material in neurons with defective mitophagy (PARK2/PARK6 patient-derived), independent of mTORC1 activity or NMDA receptor activation. Mishra SK, Hidau MK, Rai S (2021, Neurochem Int 142:104932, DOI 10.1016/j.neuint.2020.104932): memantine exerted an antidepressant-like effect by preventing hippocampal mitochondrial dysfunction and memory impairment via upregulation of CREB/BDNF signaling in a rat chronic-unpredictable-stress model, a direct drug-specific rodent study. Wang Y, Jiang B, Luo W (2022, Bioengineered 13(3):6688-6697, PMID 35235756, DOI 10.1080/21655979.2022.2026553): title and metadata indicate memantine ameliorated oxaliplatin-induced neurotoxicity via mitochondrial protection; the full abstract could not be retrieved in this session (target site returned HTTP 403; see access note), so this source is listed for completeness but not used to support specific parameter claims.

Mechanism

Enhancement of autophagic/mitophagic clearance of damaged mitochondria (VPS34-complex-dependent per Hirano et al., independent of mTORC1 and NMDA-receptor activation), alongside upregulation of CREB/BDNF signaling reported by Mishra et al. Overlaps with the Oxidative stress and ATP production entries where the same source measured more than one endpoint; see the overlap map.

Counter-evidence held on record

This is preclinical evidence only and must never be presented to a consumer as a demonstrated human mitochondrial benefit. Because one drug-specific human-cell study found genuinely bidirectional, concentration- and duration-dependent effects, this entry must not be simplified into an unqualified "protects mitochondria" claim, and it supports no supplement or dosing recommendation of any kind.

Limits on what this shows

• Key negative/null findings: McAllister J et al. (2008, Biochem Pharmacol 75(4):956-964, PMID 18053965, DOI 10.1016/j.bcp.2007.10.019), using human NT2 teratocarcinoma-derived neuronal precursor cells, found micromolar memantine concentrations affect mitochondrial peroxide production in opposite directions depending on exposure: acute exposure decreased peroxide production, while chronic exposure increased it, with effects the authors describe as occurring largely independent of NMDA channel antagonism. This is genuine counter-evidence to a uniformly protective narrative and is reported here in full rather than omitted.
• At-risk subgroups: Not established in humans; all direct evidence is preclinical.
• Counter-evidence on record: The McAllister 2008 chronic-exposure finding above; no other drug-specific study located in this review reported memantine increasing oxidative stress markers.

Regulatory status

Not addressed in the FDA label.

Population evidence

Dias CP et al. (2007, Neuroscience 146(4):1719-1725, DOI 10.1016/j.neuroscience.2007.03.018): memantine reduced oxidative damage and enhanced long-term recognition memory in aged rats, a direct drug-specific rodent study. Dabrowska-Bouta B et al. (2021, Int J Mol Sci 22(21):11330, PMID 34768760): in a rat experimental autoimmune encephalomyelitis model, memantine treatment decreased malondialdehyde levels, decreased superoxide dismutase activity, decreased protein and non-protein sulfhydryl groups versus untreated EAE rats, and increased reduced glutathione, alongside improved neurological deficit scores. Khola NUH et al. (2026, Biol Trace Elem Res, PMID 42593710, DOI 10.1007/s12011-026-05296-y): in 50 male Wistar rats given sodium arsenite (20 mg/kg) with a dedicated memantine-alone arm (10 mg/kg, n=10, 28 days, oral), memantine alone restored glutathione peroxidase, catalase, and superoxide dismutase activity in cortex and hippocampus and improved histological cellular density, with the memantine-alone group's histology outperforming the metformin-alone comparator. All three used memantine directly, not a class surrogate. A fourth, more limited source, a Journal of Receptors and Signal Transduction in vitro study of homocysteine and memantine on oxidative-stress-related TRP cation channels in an Alzheimer's model (2020;41(3), PMID 32781866), is drug-specific but its abstract could not be retrieved in this session (see access note); it is listed for completeness, not relied on for the direction claim above.

Mechanism

Proposed antioxidant action reducing lipid peroxidation and restoring endogenous antioxidant enzyme activity, plausible given memantine's glutamate-excitotoxicity-blocking mechanism, which is upstream of much oxidative calcium-mediated neuronal injury.

Counter-evidence held on record

Animal and in vitro findings do not establish a human antioxidant benefit and must never be marketed as one. The genuinely mixed McAllister 2008 result means this must not be presented to a consumer as a settled "memantine protects against oxidative stress" claim; concentration and duration both matter, and no human biomarker study was located either direction.

Limits on what this shows

• Key negative/null findings: No other drug-specific animal or human study of memantine and copper status was located in this review despite searches across PubMed search-listing pages, Crossref, and reachable Europe PMC/OpenAlex queries.
• At-risk subgroups: Not established; this is a single preclinical study in a disease model with experimentally elevated copper, not a general population finding.
• Counter-evidence on record: None found; this is the only drug-specific copper source located, so the finding is unreplicated rather than contradicted.

Regulatory status

Not addressed in the FDA label; copper status is not among labeled adverse reactions or monitoring parameters.

Population evidence

Li Z, Wang G, Zhong S, et al. (2020, Compr Psychiatry 102:152200, PMID 32892027, DOI 10.1016/j.comppsych.2020.152200): in adult male Sprague-Dawley rats given corticosterone injection and/or copper gluconate to model depression with elevated copper, memantine treatment "remarkably suppressed serum copper ion levels," with copper concentration decreased across treated groups; the authors link NMDA-receptor antagonism to copper-ion suppression as contributing to improvements in depression-related cognitive and behavioral symptoms. Memantine was tested directly, not as a class surrogate; no specific p-value or magnitude for the copper finding was retrievable from the abstract text available in this session.

Mechanism

Proposed link between NMDA-receptor antagonism and reduced serum copper ion levels in a corticosterone/copper-gluconate depression model; the precise biochemical pathway (altered ceruloplasmin, cellular copper handling, or another route) is not detailed in the retrievable abstract.

Counter-evidence held on record

This is a single unreplicated animal study in a copper-loaded depression model, not a human deficiency or excess finding. It must never be presented as a reason to supplement copper (memantine is not shown to deplete it) or to restrict dietary copper (the finding is in a copper-loaded disease model, not normal physiology); no dosing or supplement action follows from this entry.

Limits on what this shows

• Why no grade: Dual condition met: no study, at any tier, testing memantine's effect on iron status was found, so no yellow grade is supportable; and no consumer depletion or excess claim about memantine and iron circulates, so no white rebuttal applies either. The nearest material found, Ashraf GM et al. (2017, PMID 28360837), "New Insights into the Crosstalk between NMDARs and Iron," is a narrative review describing NMDA-receptor activation as promoting iron uptake and iron-induced neurotoxicity via divalent metal transporter 1 (DMT1) at the receptor-class level; it names no specific NMDA antagonist drug and is not itself an interventional study of any drug, so it does not clear the Tier C bar ("class member with real data") required for even a class-extrapolated yellow grade.

Channels tried, this review

WebSearch queries across multiple phrasings ("memantine serum iron ferritin hemoglobin," "memantine iron chelator DMT1 neuroprotection," "memantine iron overload NMDA excitotoxicity," "NMDA receptor spinal iron accumulation DMT1") returned reviews and adjacent mechanism papers but no drug-specific memantine-iron study. The Crossref Works API was queried directly and returned no matching drug-specific record. Europe PMC (www.ebi.ac.uk) and OpenAlex (api.openalex.org) direct queries for this category were blocked by this session's outbound proxy with HTTP 403/429 responses across repeated attempts and could not be completed. Direct access to pubmed.ncbi.nlm.nih.gov and eutils.ncbi.nlm.nih.gov was blocked throughout this session (HTTP 403 policy denial at the proxy), so PubMed search-listing pages could not be loaded directly for this category; WebSearch was used as the best available substitute and returned PubMed/PMC result listings without full access to the underlying abstracts in most cases.

Assessment

Genuine literature gap, with a tooling limitation layered on top rather than substituting for it: even allowing that direct PubMed and Europe PMC access were degraded this session, the WebSearch, Crossref, and general web channels that did work turned up no drug-specific iron study for memantine at all, only a receptor-mechanism review naming no specific drug. A later revision with restored PubMed/Europe PMC/OpenAlex access should re-run "memantine AND (iron OR ferritin OR DMT1)" directly against those APIs before concluding this gap is fully closed.

Limits on what this shows

• Why no grade: Dual condition met: after tracing the one apparently on-topic study to its actual methods, no Tier A, B, or C evidence measuring memantine's effect on gut microbiota composition, diversity, or function was found, so no yellow grade is supportable; and no circulating consumer claim about memantine disrupting the gut microbiome was located, so no white rebuttal applies either.

Channels tried, this review

The most relevant-looking source, "Concomitant memantine and Lactobacillus plantarum treatment attenuates cognitive impairments in APP/PS1 mice" (PMID 31907339, Aging (Albany NY) 2020, DOI 10.18632/aging.102645), was fetched directly. On close reading, its APP/PS1 disease-model experiment used four arms (PBS control, memantine alone 1 mg/mL, L. plantarum alone, and the combination, n=15 per group), but gut-microbiota metagenomic sequencing was performed only in a separate, earlier C57BL/6J wild-type experiment (n=30) used to establish a choline-diet-to-microbiota-to-TMAO mechanistic rationale; that sequencing cohort was not treated with memantine at all, and no microbiota diversity or composition data are reported for any of the memantine-treated APP/PS1 arms. This is recorded here as a genuine near-miss, not as supporting evidence. A separate search for memantine's direct antimicrobial activity found Peng L et al. (2020, Front Cell Infect Microbiol 10:47, DOI 10.3389/fcimb.2020.00047), showing memantine enhances neutrophil extracellular trap formation against a multidrug-resistant meningitic Escherichia coli strain in a systemic bloodstream/organ-dissemination infection model; this is genuine drug-specific antimicrobial pharmacology but is about host immune defense against a systemic pathogen, not gut-resident microbiota composition, so it is listed as adjacent context rather than support for a gut microbiome grade. WebSearch queries for "memantine gut microbiota," "memantine gut microbiome bacteria," and related phrasings returned only these two sources as memantine-specific. Direct PubMed, Europe PMC, and OpenAlex API access were blocked by this session's proxy for parts of this review (see the Iron entry above and the access note below).

Assessment

Genuine gap rather than a simple tooling failure: the near-miss study was actually read in full and shown not to contain the relevant data, which is a stronger basis for ungraded than an unreachable search would be. A later revision should look specifically for microbiota composition data in the memantine-treated arms of similar Alzheimer's-model gut-brain-axis studies, and should re-run direct PubMed/Europe PMC queries for "memantine AND (gut microbiota OR microbiome OR 16S)" once access is restored.

Limits on what this shows

• Key negative/null findings: The label does not characterize these events as dose-dependent, and pancytopenia/thrombocytopenia are not described as arising from a measured nutrient deficit in any source reviewed.
• At-risk subgroups: Not specified in the label beyond "postmarketing"; no subgroup analysis by age, renal function, or comedication was located.
• Counter-evidence on record: Common, trial-measured hematologic findings in the label are limited to weight increase (3% vs. 1% placebo); no trial-measured anemia, neutropenia, or thrombocytopenia signal above placebo was located in the controlled-trial adverse-reaction tables reviewed, consistent with these events being rare postmarketing reports rather than a frequent trial-level signal.

Regulatory status

Labeled postmarketing adverse reaction in the current U.S. prescribing information for Namenda XR.

Population evidence

Postmarketing pharmacovigilance data compiled by the manufacturer and FDA; the label lists agranulocytosis, leukopenia (including neutropenia), pancytopenia, thrombocytopenia, and thrombotic thrombocytopenic purpura among adverse reactions identified after approval, without a quantified incidence figure, consistent with rare, spontaneously-reported events rather than a trial-measured frequency.

Mechanism

Not established in the label; postmarketing blood dyscrasias of this kind are typically idiosyncratic and immune-mediated rather than nutrient-cofactor deficiencies. The label does not link these events to iron, copper, or B12 status, and no mechanism tying memantine's NMDA-antagonist pharmacology to bone-marrow suppression was located in this review.

Counter-evidence held on record

This is a rare, idiosyncratic hematologic adverse-reaction risk, not an iron, copper, or B12 deficiency. Per governing rule, any cytopenia identified on memantine must never be presented as a reason to supplement iron, B12, or copper; it warrants a CBC and clinical evaluation, not empiric nutrient repletion.

Limits on what this shows

• Key negative/null findings: No human ATP-production or cellular energy-metabolism study in memantine-treated patients was located in this review. The EXCLI J study did not report direct ATP concentration, oxidative phosphorylation flux, or glycolytic flux measurements, only gene/protein expression markers consistent with a metabolic shift.
• At-risk subgroups: None identified; this is an oncology-cell-line mechanistic study, not a risk signal for the treated Alzheimer's disease population.
• Counter-evidence on record: None found contradicting the direction reported; the caveat here is entirely about model relevance (cancer cell line, high fixed concentration) rather than a competing finding.

Regulatory status

Not addressed in the FDA label.

Population evidence

Albayrak G, Demirtas Korkmaz F (2021, EXCLI J 20:223-231, DOI 10.17179/excli2020-2890): A549 lung cancer cells treated with 0.25 mM memantine for 48 hours showed significant AMPK1/2 activation (p=0.039 and p=0.0105) alongside decreased expression of HIF1A, beta-catenin, and PKM, an "energetic switch" the authors link to reduced cell viability, G0/G1 cell-cycle arrest, apoptosis, and autophagy in this cancer cell line. Memantine was tested directly, not as a class surrogate, but the model is a cancer cell line under a high, fixed millimolar-range concentration, a context that does not generalize to normal neuronal or systemic energy metabolism in an Alzheimer's disease patient.

Mechanism

AMPK-mediated metabolic reprogramming; overlaps mechanistically with the Mitochondrial burden entry, since McAllister et al. 2008 (cited there) also measured oxygen consumption rate and electron-transport-chain complex activity, both directly relevant to ATP-generating capacity. See the overlap map.

Counter-evidence held on record

Single in vitro oncology-cell-line study at a high fixed concentration, no human or normal-tissue data, no dosing or supplement implication of any kind. Must never be presented as evidence that memantine raises or lowers a patient's cellular energy or "ATP levels."