Valbenazine

Limits on what this shows

• Null/negative findings: None identified; no direct valbenazine or tetrabenazine test of mitochondrial parameters exists in the sources located.
• At-risk subgroups: None established for any VMAT2-inhibitor drug in humans.

Regulatory status

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

Population evidence

Munoz et al. 2012 (as above): wild-type RCSN-3 cells exposed to aminochrome showed "dramatic remodeling of the mitochondrial inner membrane" and increased autophagy, both prevented by VMAT2 overexpression; a genetic model, not a drug study. Tinoco-Bravo & Manjarrez 2026, MicroPublication Biology, "Effects of Vitamin C Supplementation on Tetrabenazine Treatment in a Caenorhabditis elegans Huntington's Disease Model" (PMID 42438718): title, authors, journal, and year confirmed via a PubMed search-listing page under the query "tetrabenazine oxidative stress," and directly on-topic (an antioxidant tested alongside tetrabenazine), but the full abstract could not be retrieved after repeated attempts: the PubMed abstract page returned a reCAPTCHA bot-verification challenge, a Crossref bibliographic-title search did not return the record, and Europe PMC and OpenAlex per-PMID lookups both returned repeated HTTP 429 responses across multiple paced retries. Listed for completeness; not used to support the direction of this grade. Adetuyi & Wimalasena 2025, Toxics, "Exposure to Mitochondrial Toxins: An In Vitro Study of Energy Depletion and Oxidative Stress in Driving Dopaminergic Neuronal Death in MN9D Cells" (PMID 40863913): surfaced by both a "tetrabenazine oxidative stress" and a "tetrabenazine mitochondrial" PubMed search; whether tetrabenazine itself was among the "mitochondrial toxins" tested could not be confirmed through the same blocked and rate-limited channels. Listed for completeness only; not used to support this grade.

Mechanism

Same VMAT2/dopamine-oxidation pathway described under Oxidative stress: unsequestered dopamine forms reactive oxidation products that damage mitochondrial membranes.

Counter-evidence held on record

This is a genetic-model finding, not a valbenazine or tetrabenazine drug study, and should not be read as demonstrated mitochondrial harm at clinical dosing. It does not support CoQ10 or other mitochondrial-support supplementation, for which no dosing evidence exists in this drug's population. See Overlap map: Munoz et al. 2012 is shared with Oxidative stress and ATP production.

Limits on what this shows

• Null/negative findings: None identified. No study has directly tested oxidative-stress markers in valbenazine- or tetrabenazine-treated tissue at clinical exposure, so there is also no null result to report on this drug, only an absence of direct testing.
• At-risk subgroups: None established in humans on any VMAT2-inhibitor drug. The Sakano beta-cell finding raises an unconfirmed, mechanistically plausible connection to valbenazine's own labeled "blood glucose increased" adverse reaction (see Monitoring panel), but this connection has not been tested and is not itself evidence for this grade; it is a labeled clinical outcome (Hard Rule 2), not a nutrient/category finding, and is noted here only as context.

Regulatory status

Not addressed in FDA labeling.

Population evidence

Munoz et al. 2012, Biochim Biophys Acta, in vitro, RCSN-3 (rat substantia-nigra-derived) cells engineered to overexpress VMAT2 (7-fold) and DT-diaphorase (9-fold): overexpression produced a 6-fold reduction in cell death (P<0.001) on exposure to aminochrome, a reactive dopamine-oxidation product, versus wild-type cells, which showed "dramatic remodeling of the mitochondrial inner membrane," increased autophagy, and apoptotic DNA laddering. This is a genetic manipulation of VMAT2 expression, not a study of any pharmacological VMAT2 inhibitor. Sakano et al. 2020, Diabetes, in vivo, beta-cell-specific VMAT2 knockout mice under high-fat-diet stress: the authors state that "VMAT2 uptake of dopamine protects dopamine from degradation by monoamine oxidase, thereby safeguarding beta-cells from excess reactive oxygen species (ROS) exposure"; knockout mice showed initially elevated insulin secretion followed by impaired glucose tolerance and progressive beta-cell dysfunction. Again a genetic knockout in non-neuronal (pancreatic) tissue, not a drug study. Choi, Kim & Xia 2015, Toxicology, in vitro: "JNK inhibition of VMAT2 contributes to rotenone-induced oxidative stress and dopamine neuron death," a pharmacologically adjacent pathway (JNK-mediated functional impairment of VMAT2) in a rotenone Parkinson's-disease model, still not a VMAT2-inhibitor drug study. Guillot et al. 2008, J Neurochem, in vivo, genetic VMAT2 low-expression mice: reduced vesicular dopamine storage "exacerbates methamphetamine-induced neurodegeneration and astrogliosis," a further genetic, non-pharmacological line of convergent evidence.

Mechanism

Dopamine not sequestered into synaptic vesicles by VMAT2 is vulnerable to autoxidation into reactive quinones such as aminochrome, and to monoamine-oxidase-mediated oxidative deamination, which generates hydrogen peroxide; both pathways generate reactive oxygen species. This is established basic pharmacology of the VMAT2 target itself, not a valbenazine-, tetrabenazine-, or deutetrabenazine-specific finding.

Counter-evidence held on record

Every supporting source is a genetic knockout/overexpression model or a pharmacologically adjacent pathway (JNK/rotenone), not a study of valbenazine, tetrabenazine, deutetrabenazine, or any marketed VMAT2-inhibitor drug. This is mechanistic plausibility from basic transporter biology, not evidence that valbenazine at clinical dosing measurably increases oxidative stress in patients, and it should not be used to justify antioxidant supplementation, for which no dosing evidence exists in this drug's population. Two further title-confirmed sources (Tinoco-Bravo & Manjarrez 2026, vitamin C plus tetrabenazine in C. elegans; Adetuyi & Wimalasena 2025, mitochondrial-toxin exposure in MN9D cells) could not be opened this session (see Sources) and were not used to support this grade. See Overlap map: Munoz et al. 2012 is shared with Mitochondrial burden and ATP production.

Limits on what this shows

• Why no grade: Both conditions for ungraded remain met: no Tier B or Tier C evidence supports even a yellow grade, and no circulating consumer claim specific to valbenazine, tetrabenazine, or deutetrabenazine and copper was found. The three-label Tier A review strengthens this as a genuine evidence gap rather than a purely tooling-limited one, though the blocked search channels mean a later revision with different access should still re-attempt PubMed, Crossref, Europe PMC, and Semantic Scholar directly for this term, since none of those returned a genuine content-based result this session, only access blocks.

Channels tried

Re-researched in a dedicated follow-up pass with its own full tool budget. Original session: dedicated PubMed query "valbenazine AND copper" (clean, zero results); broader OR-combined PubMed queries (no drug-specific hits); full Crossref bibliographic catalog for "valbenazine" (50 records, 2016 to 2026) screened for any mineral-related title, none found; Drugs.com and RxList checked directly, none found. This follow-up pass added: all three marketed VMAT2-inhibitor regulatory labels (valbenazine/Ingrezza, tetrabenazine/Xenazine, deutetrabenazine/Austedo) fetched directly via the openFDA label API and their Adverse Reactions, Warnings and Precautions, and Clinical Pharmacology sections searched line by line for "copper"; none found in any of the three. OpenAlex's per-PMID single-record lookup endpoint successfully retrieved full abstracts for the two sources the original session could not open (PMID 42438718, vitamin C plus tetrabenazine in C. elegans; PMID 40863913, mitochondrial-toxin exposure in MN9D cells); neither abstract mentions copper or any mineral, and neither bears on this category. Fresh attempts to re-query PubMed's search-listing pages, the Crossref API, the Europe PMC REST API, the Semantic Scholar API, OpenAlex's general search endpoint, DailyMed, and NCBI E-utilities for "tetrabenazine copper," "VMAT2 copper," and related phrasings were blocked on every attempt across more than a dozen calls paced 20 to 90 seconds apart: PubMed, Europe PMC, DailyMed, and NCBI E-utilities returned proxy-level HTTP 429 rejections or robots.txt disallowals; Crossref, Semantic Scholar, and OpenAlex's general search endpoint returned genuine HTTP 429 responses from the host itself, unchanged after long waits. This pattern is consistent with this environment's disclosed organization-level access constraint rather than a transient rate limit. A mechanistic angle was also considered: dopamine-beta-hydroxylase, the copper-dependent enzyme that converts dopamine to norepinephrine, acts downstream of VMAT2's transport step, offering no plausible depletion pathway even if reasoned through rather than literature-confirmed.

Outcome

Clean negative confirmed on an expanded evidence base: the original PubMed zero-result count now sits alongside a completed, successful Tier A review of all three VMAT2-inhibitor labels finding no copper mention in any of them. Every further literature-search channel attempted this session was blocked at the proxy or host level rather than returning content, which is disclosed above as a tooling limitation distinct from the completed, genuine negative label review.

Limits on what this shows

• Why no grade: Both conditions for ungraded remain met: no Tier B or Tier C evidence to support even yellow, and no circulating claim to rebut as white. Treated as a genuine evidence gap for this drug and its class, strengthened by the three-label Tier A review, with the same caveat as Copper that a later revision with different access should re-attempt the blocked search channels directly.

Channels tried

Re-researched in a dedicated follow-up pass with its own full tool budget. Original session: dedicated PubMed query "valbenazine AND iron" (clean, zero results); same broader OR-combined queries as the Copper entry (no drug-specific hits); full Crossref bibliographic catalog for "valbenazine" (50 records) screened, none found; Drugs.com and RxList checked directly, none found. This follow-up pass added the same three-label direct review described under Copper (valbenazine/Ingrezza, tetrabenazine/Xenazine, deutetrabenazine/Austedo, via the openFDA label API): none of the three labels' Adverse Reactions, Warnings and Precautions, or Clinical Pharmacology sections mention iron, ferritin, or iron-deficiency anemia. OpenAlex's per-PMID lookup again retrieved both previously inaccessible PMIDs (42438718, 40863913); neither mentions iron and neither bears on this category. The same set of fresh re-query attempts against PubMed, Crossref, Europe PMC, Semantic Scholar, OpenAlex's general search endpoint, DailyMed, and NCBI E-utilities for "tetrabenazine iron," "VMAT2 iron," and related phrasings were made and blocked identically to Copper, paced 20 to 90 seconds apart, consistent with the same organization-level access constraint. A mechanistic angle was considered: tyrosine hydroxylase, the iron-dependent rate-limiting enzyme in catecholamine synthesis, acts upstream of VMAT2's vesicular-storage step, offering no plausible depletion pathway on reasoning alone.

Outcome

Clean negative confirmed on an expanded evidence base, as under Copper: the original PubMed zero-result count now sits alongside a completed Tier A review of all three VMAT2-inhibitor labels finding no iron mention. Further literature-search channels were blocked at the proxy or host level rather than returning content.

Limits on what this shows

• Why no grade: Both conditions for ungraded remain met. Treated as a genuine evidence gap for this drug and its class, strengthened by the three-label Tier A review; a later revision with different access should re-attempt the blocked search channels directly, and specifically check whether any VMAT1-focused gut literature exists that might bear on VMAT2-selective inhibitors by contrast.

Channels tried

Re-researched in a dedicated follow-up pass with its own full tool budget. Original session: dedicated PubMed query "valbenazine AND microbiome" (clean, zero results); broader OR-combined queries (no drug-specific hits); full Crossref bibliographic catalog for "valbenazine" (50 records) screened, none found; Drugs.com and RxList checked directly, none found. This follow-up pass added the same three-label direct review described under Copper: none of the valbenazine, tetrabenazine, or deutetrabenazine labels mention gut microbiome, flora, or GI bacteria in any section. The labels do show a labeled GI adverse reaction, diarrhea, for two of the three drugs (valbenazine 4.7% vs. 1.6% placebo in the chorea trials; deutetrabenazine 9% vs. 0% placebo), but neither label offers a microbiome-composition or mechanistic explanation for it, so under Hard Rule 2 a GI symptom rate alone is a clinical outcome, not a measured microbiome-composition change, and cannot be used to support a yellow grade here; it is noted for transparency only. OpenAlex's per-PMID lookup again retrieved both previously inaccessible PMIDs (42438718, 40863913); neither concerns the gut microbiome. The same set of fresh re-query attempts against PubMed, Crossref, Europe PMC, Semantic Scholar, OpenAlex's general search endpoint, DailyMed, and NCBI E-utilities for "tetrabenazine microbiome," "tetrabenazine gut flora," and related phrasings were made and blocked identically to Copper and Iron, paced 20 to 90 seconds apart.

Outcome

Clean negative confirmed on an expanded evidence base: the original PubMed zero-result count now sits alongside a completed Tier A review of all three VMAT2-inhibitor labels finding no microbiome mention, and a labeled diarrhea rate that does not qualify as microbiome evidence under Hard Rule 2. VMAT2 is predominantly a neuronal and neuroendocrine transporter (with the beta-cell finding elsewhere in this dossier as one documented exception); peripheral serotonin storage in enterochromaffin cells relies mainly on VMAT1, which offers a plausible reason a gut-microbiome effect was not found, but this reasoning is not itself literature-confirmed and is not used as a substitute for a search result. Further literature-search channels were blocked at the proxy or host level rather than returning content.

Limits on what this shows

• Null/negative findings: None identified; no direct valbenazine or tetrabenazine test of ATP levels exists in the sources located.
• At-risk subgroups: None established for any VMAT2-inhibitor drug in humans.

Regulatory status

Not addressed in FDA labeling.

Population evidence

Munoz et al. 2012 (as above): VMAT2-overexpressing RCSN-3 cells preserved ATP levels on aminochrome exposure, "contrasting sharply" with wild-type cells, which showed depleted ATP alongside mitochondrial ultrastructure damage and apoptosis markers; a genetic model, not a drug study. Adetuyi & Wimalasena 2025 (PMID 40863913, as above) is titled around "energy depletion" in dopaminergic MN9D cells exposed to mitochondrial toxins, and was surfaced by tetrabenazine-focused PubMed searches, but whether tetrabenazine was one of the toxins tested could not be confirmed given the same access blocks described under Mitochondrial burden. Listed for completeness only; not used to support this grade.

Mechanism

Same VMAT2/dopamine-oxidation pathway: mitochondrial damage from unsequestered dopamine's oxidation products impairs oxidative phosphorylation and depletes ATP; this is the same underlying experiment as the Mitochondrial burden entry, not an independent confirmation (see Overlap map).

Counter-evidence held on record

This is a genetic-model finding, not a valbenazine or tetrabenazine drug study, and does not establish an ATP-production deficit at clinical dosing. It does not support CoQ10 or other ATP-targeted supplementation, for which no dosing evidence exists in this drug's population. See Overlap map: Munoz et al. 2012 is shared with Oxidative stress and Mitochondrial burden; do not count the three entries as independent confirmations of one another.

Limits on what this shows

• Why no grade: Both conditions for ungraded remain met. Treated as a genuine evidence gap for this drug and its class, not a tooling-limited one, given the clean and complete negative results across multiple phrasings and now a direct three-label Tier A review, though a later revision with different access should still re-attempt the blocked search-engine channels directly.

Channels tried

Re-researched in a dedicated follow-up pass with its own full tool budget. Original session: dedicated PubMed query "valbenazine AND (hemoglobin OR hematocrit OR oxygen)" (zero valbenazine-specific results; PubMed's spell-correction reinterpreted the term as "valienamine," an unrelated compound); broader OR-combined queries (no drug-specific hits); full Crossref bibliographic catalog for "valbenazine" (50 records) screened, none found; Drugs.com and RxList checked directly, none found; FDA label Warnings/Precautions and Adverse Reactions reviewed directly. This follow-up pass added the same three-label direct review described under Copper, this time via the openFDA label API rather than manual reading: none of the valbenazine, tetrabenazine, or deutetrabenazine labels' Adverse Reactions, Warnings and Precautions, or Clinical Pharmacology sections mention hemoglobin, hematocrit, anemia, red blood cells, or oxygen delivery. QT prolongation remains labeled for valbenazine but is the drug's own intended-adjacent cardiac electrophysiology effect, not an oxygen-delivery or hematologic finding, and stays excluded from grading under Hard Rule 2. OpenAlex's per-PMID lookup again retrieved both previously inaccessible PMIDs (42438718, 40863913); neither concerns hemoglobin, hematocrit, or oxygen delivery. The same set of fresh re-query attempts against PubMed, Crossref, Europe PMC, Semantic Scholar, OpenAlex's general search endpoint, DailyMed, and NCBI E-utilities for "tetrabenazine hemoglobin," "tetrabenazine anemia," and related phrasings were made and blocked identically to the other three categories, paced 20 to 90 seconds apart.

Outcome

Clean negative confirmed on an expanded evidence base: the original PubMed zero-result count now sits alongside a completed Tier A review of all three VMAT2-inhibitor labels finding no hemoglobin, hematocrit, anemia, or oxygen-delivery mention in any of them. Further literature-search channels were blocked at the proxy or host level rather than returning content.