Riluzole

Limits on what this shows

• Key negative/null findings: This session could not retrieve the paper's full text (only title, author, journal, year, and a reconstructed abstract were accessible; the PubMed abstract page itself returned an empty rendering to non-browser fetches), so the precise wording and full extent of a phrase suggesting riluzole "significantly inhibited mitochondrial electron transport chain function" could not be independently disambiguated between riluzole protecting against SOD1/azide-induced electron-transport-chain disruption versus riluzole suppressing normal electron-transport-chain activity on its own; this is disclosed explicitly rather than resolved by inference, and the claim above is deliberately written to reflect only what the title and retrieved abstract text directly support.
• At-risk subgroups: None established in humans; cell and animal mechanistic evidence only.

Regulatory status

Not addressed in the current US label.

Population evidence

Jaiswal MK. "Riluzole But Not Melatonin Ameliorates Acute Motor Neuron Degeneration and Moderately Inhibits SOD1-Mediated Excitotoxicity Induced Disrupted Mitochondrial Ca2+ Signaling in Amyotrophic Lateral Sclerosis." Frontiers in Cellular Neuroscience, 2017; PMID 28111541. Cohort: SH-SY5Y neuroblastoma cells, both wild-type and G93A-SOD1-transfected, and brainstem tissue from symptomatic adult SOD1G93A transgenic mice, with riluzole itself as the tested agent (melatonin was tested in parallel and found not to replicate the effect). Riluzole moderately reduced pathologically elevated intracellular calcium transients and reversibly inhibited calcium-signal disruption in motor neurons exposed to a mitochondrial stressor (sodium azide), in both the SOD1-mutant and excitotoxic-stress contexts.

Mechanism

Named, and shared with riluzole's core labeled pharmacology: riluzole's antiglutamatergic, sodium-channel-blocking, and glutamate-release-inhibiting actions reduce excitotoxic calcium influx; this study extends that same mechanism into the mitochondrial-calcium-handling domain rather than describing a separate, additional mitochondrial action.

Counter-evidence held on record

The broader ALS pathophysiology literature (for example Mitsumoto et al., "ALS: An Organism-Wide Bioenergetic Failure Due to Mitochondrial Dysfunctions?", Biomolecules, 2026) describes mitochondrial dysfunction as a feature of the disease process itself, present independent of riluzole treatment; that disease-intrinsic literature is excluded here as evidence for a drug effect and is named only as the counter-context that keeps this entry bounded to riluzole's own mechanism. This is cell and animal mechanistic evidence of riluzole's known intended action, not a demonstrated independent mitochondrial benefit in humans, and must not be read as "riluzole protects your mitochondria" as a selling point distinct from its approved use in slowing ALS progression. It is not a reason to seek out or expect mitochondrial-support effects from riluzole beyond its labeled indication.

Limits on what this shows

• Key negative/null findings: Desnuelle C, Dib M, Garrel C, Favier A. "A double-blind, placebo-controlled randomized clinical trial of alpha-tocopherol (vitamin E) in the treatment of amyotrophic lateral sclerosis." Amyotrophic Lateral Sclerosis and Other Motor Neuron Disorders, 2001; PMID 11465936. This 289-patient trial, with all participants on background riluzole, found no effect of vitamin E on the primary outcome (rate of functional deterioration) or on survival, though vitamin E recipients showed a measurable secondary-marker improvement (increased plasma glutathione peroxidase activity, decreased thiobarbituric-acid-reactive substances, both p less than 0.05) and progressed less often from milder to severe disease states (p=0.046). This trial does not measure whether riluzole itself changes oxidative-stress markers; it tests whether adding an antioxidant helps ALS's own disease course on a riluzole background, and is cited here as the relevant human counter-context, not as evidence that riluzole causes oxidative stress.
• At-risk subgroups: None established for a riluzole-specific effect in humans; the guinea-pig ototoxicity-protection finding has not been tested in ALS patients or in humans generally.

Regulatory status

Not addressed in the current US label.

Population evidence

Ustun Bezgin S, Uygur KK, Gokdogan C, Elmas C, Goktas G. "The Effects of Riluzole on Cisplatin-induced Ototoxicity." International Archives of Otorhinolaryngology, 2019. Guinea pigs were divided into a saline-control group and two riluzole-dose groups, each given riluzole before cisplatin administration. Riluzole-treated groups had significantly less hearing loss at 8,000 Hz than controls, with microscopic analysis of inner-ear structures confirming a protective effect; the authors describe riluzole as having neuroprotective, antioxidant, and antiapoptotic properties and conclude riluzole "may have a protective effect on cisplatin-induced ototoxicity."

Mechanism

Named at Tier B: riluzole's antioxidant and antiapoptotic chemistry is proposed to blunt cisplatin's own oxidative and apoptotic damage to inner-ear hair cells; this is a separate insult (cisplatin) being counteracted by riluzole's own redox chemistry, not riluzole treating an oxidative-stress state that it itself caused.

Counter-evidence held on record

No source located shows riluzole elevating oxidative-stress biomarkers in any species; ALS itself carries a well-documented, disease-intrinsic oxidative burden distinct from anything attributable to riluzole, and the Desnuelle 2001 trial's null primary-outcome result argues against high-dose antioxidant supplementation being a meaningful lever on top of riluzole regardless of mechanism. This is a single-species animal finding in a non-ALS context (cisplatin ototoxicity), not evidence that riluzole users should take or need extra antioxidants, and not a demonstrated human benefit. It is not a reason to add high-dose vitamin E or other antioxidant supplements independently of a prescriber's guidance; see Fails verification below for the specific antioxidant-supplementation claims this evidence base does and does not support.

Limits on what this shows

• Why no grade: This category was searched with multiple phrasings ("riluzole copper," "riluzole copper zinc," "riluzole copper zinc superoxide dismutase," "riluzole copper ceruloplasmin," "riluzole metal homeostasis") across PubMed, Europe PMC, Crossref, OpenAlex, and Semantic Scholar. The only riluzole-specific result surfaced, Snow, Turnbull, da Silva, Jiang, and Tarnopolsky, "Creatine supplementation and riluzole treatment provide similar beneficial effects in copper, zinc superoxide dismutase (G93A) transgenic mice," Neuroscience, 2003 (PMID 12809687), uses "copper, zinc superoxide dismutase" only as the full formal name of the SOD1G93A disease model, not as a measurement of copper nutrient status, and does not report copper, ceruloplasmin, or any other copper-related biomarker; it is excluded here under the cohort/mechanism test as not actually addressing copper. ALS's own literature on brain copper dysregulation is tied specifically to SOD1 genetics and to investigational copper-delivery compounds such as CuATSM, none of which involve riluzole as the tested agent and all of which are disease-intrinsic or a different drug's mechanism, excluded per Hard Rule 2 and the cohort test. No consumer or practitioner claim that riluzole affects copper status was located (a general drug-reference consumer page for riluzole was checked and named no such interaction). Assessment: a genuine literature gap for this drug specifically, not a tooling failure; the search channels used did return results, just none that passed the cohort test for riluzole and copper together.

2026-09-30 revision re-check

A dedicated re-research pass repeated a PubMed search-listing query for "riluzole copper" and reviewed all 11 results returned: general ALS pathophysiology reviews with no riluzole-copper data (Al-Chalabi and Leigh 2000; Bruneteau et al. 2004; Howard and Orrell 2002; Charles and Swash 2001; Vucic and Kiernan 2009; Costa et al. 2010), an unrelated chalcogen-chemistry paper (Ghiazza et al. 2019), the SOD1 mutant-mouse founding paper (Gurney et al. 1998, disease model, not a copper measurement), the Snow et al. 2003 paper already excluded above, and a 2023 CuATSM trial, Yang et al., "Treatment with the copper compound CuATSM has no significant effect on motor neuronal pathology in patients with ALS," which tests CuATSM, an investigational copper-delivery compound, not riluzole, and so fails the Hard Rule 6 cohort test for this drug regardless of its own rigor. Crossref and OpenAlex search-endpoint queries for this category returned server errors or were rejected by this session's outbound proxy as policy denials (recorded in the proxy's connection log as HTTP 403 responses on api.crossref.org and api.openalex.org) rather than returning further results; PubMed's own abstract pages and Europe PMC's REST API were likewise blocked this session, a rate-limit and access-policy picture consistent with, and no better than, the original review. No new copper-status evidence for riluzole was found. The gap stands, re-confirmed rather than merely repeated.

Limits on what this shows

• Why no grade: This category was searched with multiple phrasings ("riluzole iron," "riluzole iron ferroptosis," "riluzole copper iron metal") across PubMed, Europe PMC, Crossref, and OpenAlex. Results returned were ALS ferroptosis and iron-handling papers that either did not test riluzole (for example an iPSC-neuron ferroptosis study that tested edaravone, a different ALS drug with a distinct free-radical-scavenging mechanism, excluded under Hard Rule 6's cohort-test requirement for class extrapolation since it was not itself tested on riluzole and its mechanism is not shared with riluzole) or described ALS's own disease-intrinsic iron and ferroptosis biology (SOD1-linked, motor-neuron-intrinsic), excluded under Hard Rule 2. The labeled overdose finding of methemoglobinemia (see Oxygen delivery/utilization, orange) concerns the oxidation state of iron already bound in hemoglobin, not iron intake, absorption, or storage status, and is deliberately kept out of this entry under the direction-check required by Hard Rule 4: it is an oxygen-delivery finding, not an iron-nutrient finding. No consumer or practitioner claim that riluzole affects iron status was located. Assessment: a genuine literature gap for a drug-specific iron-nutrient effect, distinct from the well-populated but non-riluzole-specific ALS ferroptosis literature.

2026-09-30 revision re-check

A dedicated re-research pass repeated a PubMed search-listing query for "riluzole iron" and reviewed all results returned, including two new candidates not in the original review: Raghubir et al. 2020 and Rampersaud et al. 2016, both nanotechnology studies using dextran-coated iron-oxide nanocages as a drug-delivery vehicle for riluzole in cancer-cell models (osteosarcoma; general nanoparticle drug release), excluded because they test iron oxide as a carrier material, not as a measure of the body's iron status, and are not ALS or ALS-drug studies at all. A third result, Koh JY et al., "Antioxidative and proapoptotic effects of riluzole on cultured cortical neurons," Journal of Neurochemistry, 1999, is genuinely riluzole-specific: riluzole attenuated oxidative injury induced by exposure to iron(III) chloride (FeCl3) in cultured cortical neurons. This is excluded from the Iron entry on the same category-mismatch reasoning applied to Snow et al. 2003 under Copper above: FeCl3 in this assay is a Fenton-reaction pro-oxidant reagent used to chemically challenge the cells with free radicals, the same experimental role that cisplatin plays in the already-graded Oxidative stress yellow entry, not a model of iron absorption, storage, transport, or deficiency/overload status. Properly read, this is an oxidative-stress-protection finding that happens to use an iron salt as its oxidant, not an iron-nutrient finding, so it does not support an Iron grade under this dossier's category definitions; it is disclosed here rather than silently discarded so a reader can see it was found and weighed. This session's PubMed abstract pages, Europe PMC REST API, and Crossref API were substantially blocked (rate limits and, per this session's proxy log, HTTP 403 policy-level connection denials on eutils.ncbi.nlm.nih.gov, pubmed.ncbi.nlm.nih.gov, api.crossref.org, and www.ebi.ac.uk), so a stable PMID for the Koh et al. 1999 paper could not be independently confirmed this session; it is named here by title, journal, and year only, and is not added to the numbered Sources list pending that confirmation. No riluzole-specific iron-status evidence was found. The gap stands, re-confirmed with one new source considered and excluded for cause.

Limits on what this shows

• Key negative/null findings: This is a single animal study; the Methods measured tight-junction protein expression, intestinal permeability (fluorescein-dextran absorption), serum LPS, and cytokine panels, not gut microbiome composition or diversity directly (no 16S sequencing or taxonomic analysis was performed). The authors explicitly flag characterizing the microbiota itself as future work. No human data on riluzole and intestinal barrier function or microbiome composition was located.
• At-risk subgroups: None established in humans; this is preclinical, mouse-model evidence only.

Regulatory status

Not addressed in the current US label.

Population evidence

Zhang Y, Robinson K, Xia Y, Sun J. "Synergistic Effects of Riluzole and Sodium Butyrate on Barrier Function and Disease Progression of Amyotrophic Lateral Sclerosis Through the Gut-Neuron Axis." Comprehensive Physiology, 2025 (open access, PMC11966087). SOD1G93A transgenic ALS mice, 9 to 10 weeks old, n=8 to 10 per group, were treated for 6 weeks with riluzole alone (10 mg/kg intraperitoneal daily), sodium butyrate alone, the combination, or no treatment. Riluzole-only mice, compared with untreated control mice, showed statistically significant increases in the colonic tight-junction proteins ZO-1 and Claudin-5, a statistically significant decrease in serum lipopolysaccharide, a statistically significant decrease in the inflammatory cytokine IL-17, and a statistically significant decrease in h-SOD1G93A protein aggregation in the colon. IL-6 and interferon-gamma decreased without reaching statistical significance in the riluzole-only group. The riluzole/sodium-butyrate combination exceeded riluzole-only results on every measure.

Mechanism

Not fully established. The authors propose histone-deacetylase inhibition and reduced inflammatory cytokine signaling as a candidate shared route for both agents, but state directly that "the mechanism underlying the synergistic effects...remains unknown," and that riluzole's own contribution to intestinal barrier function had not been described in the literature before this study.

Counter-evidence held on record

No source located contradicts this finding, but it has not been independently replicated, and it measures barrier permeability and endotoxin translocation rather than microbiome composition or diversity in the literal sense the category name suggests; that distinction is stated here so a reader does not read this as a microbiome-sequencing result. This is animal-only, single-study, mechanistic evidence of a protective effect, not a demonstrated human benefit, and not a reason to expect or seek out gut-health effects from riluzole. It does not indicate any need for probiotic, prebiotic, or fiber supplementation, and no dosing recommendation follows from it.

Limits on what this shows

• Key negative/null findings: Methemoglobinemia does not appear among the label's common (5 percent or greater) adverse reactions from controlled clinical trials, only in the overdose-specific section, consistent with this being an uncommon, dose-bounded effect rather than a routine therapeutic-dose finding.
• At-risk subgroups: Patients with intentional or accidental massive overdose; patients with glucose-6-phosphate dehydrogenase deficiency or other predispositions to methemoglobinemia may plausibly be at higher risk from any oxidizing drug exposure, though no riluzole-specific data on this subgroup was located.

Regulatory status

Tier A. The current US label's Overdosage section lists methemoglobinemia among reported symptoms following ingestion of 1.5 to 3 grams (30 to 60 times the recommended 50 mg twice-daily dose), alongside acute toxic encephalopathy, coma, drowsiness, and memory loss. No incidence rate is given.

Population evidence

Label-level overdose reporting (Tier A) plus two independent published case reports located on a dedicated search: Viallon, Page, and Bertrand, New England Journal of Medicine, 2000, and Woolf, Carstairs, and Tanen, Annals of Emergency Medicine, 2004, both titled around riluzole-induced methemoglobinemia. Both are short correspondence-format case reports; this session could not retrieve their full case-detail text (abstract fields were not populated in the bibliographic APIs reached), so whether either patient's exposure was itself an overdose or occurred at standard therapeutic dosing could not be independently confirmed and is disclosed as an open question for a reader consulting the primary source.

Mechanism

Not detailed in the sources located. Methemoglobinemia in general reflects oxidation of hemoglobin's heme iron from the ferrous (Fe2+) to the ferric (Fe3+) state, which cannot bind oxygen; no source specific to riluzole describes the chemical step by which riluzole or its metabolites drive this oxidation.

Counter-evidence held on record

No source located reports methemoglobinemia at standard 50 mg twice-daily dosing; the label places it specifically in the overdose-symptom list, and it is absent from the common adverse-reaction table drawn from controlled trials at therapeutic dose. This is not an iron deficiency and not a reason to supplement iron; methemoglobin is a functional oxidation-state problem in existing hemoglobin, not a shortage of iron itself, and treatment for symptomatic methemoglobinemia is a medical emergency (methylene blue and supportive care), not a nutrient intervention. Any suspected riluzole overdose requires immediate emergency evaluation.

Limits on what this shows

• Why no grade: This category was searched with multiple phrasings ("riluzole mitochondrial ATP," "riluzole mitochondrial ATP synthesis," "riluzole mitochondrial respiration," "riluzole permeability transition," "riluzole mitochondria") across PubMed, Europe PMC, Crossref, OpenAlex, and Semantic Scholar, repeated across the session as rate limits eased. Results consistently surfaced either ALS disease-intrinsic bioenergetics reviews (for example Mitsumoto et al., "ALS: An Organism-Wide Bioenergetic Failure Due to Mitochondrial Dysfunctions?", Biomolecules, 2026, and Heffernan et al., "Disrupted astrocyte-neuron metabolic coupling in amyotrophic lateral sclerosis," Frontiers in Cell and Developmental Biology, 2026, both excluded under Hard Rule 2 as describing the disease rather than the drug), other ALS-candidate drugs not sharing riluzole's mechanism (for example mitochonic acid 5, UA-30), or the Snow et al. 2003 riluzole-versus-creatine comparison (PMID 12809687), which the retrieved abstract data confirms did not measure ATP, mitochondrial respiration, or energy metabolism directly. This session's network access to the primary search and abstract APIs (PubMed, Europe PMC, Crossref, OpenAlex, Semantic Scholar) was degraded throughout by repeated HTTP 429 rate-limit responses, and PubMed's individual abstract pages returned a Google reCAPTCHA challenge to non-browser fetches later in the session; most queries eventually succeeded after retrying with spacing across alternate channels, so this reflects a genuine literature gap for a riluzole-specific ATP-production finding at the tiers that could be verified this session, not an unattempted search, though a future revision attempted when these channels are fully open should re-check this category first given how degraded access was throughout.

2026-09-30 revision re-check

Per the flag in the prior review, this revision specifically re-attempted full-text access to the Jaiswal 2017 paper (PMID 28111541, cited under the already-graded Mitochondrial burden yellow entry), since it is the one source in this dossier that touches a mitochondrial-function marker (NADH fluorescence) that bears on ATP production. Direct retrieval from the publisher, Frontiers in Cellular Neuroscience, succeeded this time (the PubMed and Europe PMC routes used previously remained blocked). The confirmed sentence reads: "there was a slight increase in the NADH fluorescence in presence of 100 uM riluzole compared to aCSF but there was no significant difference." This resolves the earlier disclosed ambiguity about whether riluzole affects baseline electron-transport-chain activity: the paper's own data show no statistically significant change in this marker from riluzole alone, so this source provides a confirmed null result for a riluzole-specific ATP/electron-transport effect, not supporting evidence, and does not move ATP production out of ungraded. Fresh queries this pass for "riluzole oxidative phosphorylation," "riluzole mitochondrial complex," and "riluzole mitochondrial respiration ATP" against Crossref, OpenAlex's search endpoint, and Semantic Scholar's search endpoint returned server errors (503), rate limits (429), or, per this session's proxy connection log, outright HTTP 403 policy-level denials on api.crossref.org, api.openalex.org, and api.semanticscholar.org, so no further candidate sources could be surfaced through those channels this session; this is disclosed as a channel-access limitation, not as a completed and clean search of those specific databases. No riluzole-specific ATP-production evidence was found. The gap stands, with the one previously flagged access gap now closed and returning a null result rather than an unknown.