Chlorpheniramine

Limits on what this shows

• Null findings: PubMed listing "chlorpheniramine mitochondria" returned five records; only this one reported chlorpheniramine affecting mitochondrial function. Two other records indexed under chlorpheniramine pharmacology and mitochondria were identified on repair from OpenAlex metadata only: PMID 4572030 is Rhodes and Wilkie 1973 (Biochem Pharmacol), antimitochondrial activity of lampren in S. cerevisiae, with chlorpheniramine, mitochondria (drug effects) and oxygen consumption (drug effects) as MeSH terms, no abstract, so chlorpheniramine's role in it is unknown [23]; PMID 173380 is Nakamura 1975 (Br J Exp Pathol), rat renal subcellular fractions and vascular permeability, whose abstract does not mention chlorpheniramine or mitochondrial effects [24]. Neither is used as support. The 2026 Europe PMC search for chlorpheniramine with mitochondria, ATP or oxygen consumption surfaced no mammalian mitochondrial study of the drug [20].
• At-risk subgroups: None identified.

Direction

Possible burden (impairment of respiratory function), model organism only.

Regulatory status

Not mentioned in the OTC labels [1][2].

Population evidence

Marmiroli 1985 [10], petite-negative yeasts (Candida utilis, C. albicans, C. tropicalis) and S. cerevisiae: six CNS drugs inhibited growth; chlorpromazine and chlorpheniramine were the most effective and affected respiration and cytochrome biosynthesis. The abstract gives no concentration for chlorpheniramine, so relevance to human exposure cannot be judged. Read via PubMed record through a summarizing fetch tool. Full text not opened.

Mechanism

Named only generally (respiration and cytochrome synthesis in yeast). No mammalian electron-transport or membrane-potential data located.

Hunt result (red/orange)

No human or mammalian study with chlorpheniramine as exposure and a mitochondrial measure. No second source. Ceiling is yellow (Tier B).

Counter-evidence held on record

Counter-evidence and confounding Yeast growth inhibition at unknown concentration is often not predictive of human tissue effects. Classic H1 antihistamines are highly lipophilic [6], so nonspecific in vitro effects at high concentrations are possible; this is a general caution, not a finding for chlorpheniramine. Framing caution Hypothesis-generating only. Do not state that chlorpheniramine damages mitochondria in people.

Limits on what this shows

• Null findings: None found. No human study of chlorpheniramine with MDA, SOD, glutathione or total antioxidant capacity was located (PubMed listing for "chlorpheniramine oxidative stress" was blocked by 429 on two attempts; a listing for "chlorpheniramine body weight" surfaced this paper).
• At-risk subgroups: None identified. Not applicable to people.

Direction

Reverse (protective). Not a depletion and not an excess finding.

Regulatory status

Not mentioned in the OTC labels opened [1][2].

Population evidence

Al-Amri 2023 [9]: 18 male Wistar rats (180 to 200 g), 3 groups of n = 6 (saline control, forced-swim acute stress, chlorpheniramine 10 mg/kg i.p. then stress). In hippocampus, MDA rose with stress (p ≤ 0.0001) and fell with chlorpheniramine (p ≤ 0.0001) but was not restored to control; SOD fell with stress (p ≤ 0.0001) and rose with chlorpheniramine (significant, p not given in text). IL-6 and IL-1β followed the same pattern. Cortex Nrf2 and BDNF mRNA rose versus stress (Nrf2 p ≤ 0.0001, still below control at p = 0.0303). Numeric group means were in a figure only. GSH, catalase and ROS were not measured. Source read as abstract via OpenAlex reconstruction plus the full MDPI article via a summarizing fetch tool.

Mechanism

Named by the authors: Nrf2-BDNF pathway activation with lower inflammatory mediators. Not a nutrient mechanism.

Hunt result (red/orange)

One animal study, brain tissue only, single dose, no dose-response, mRNA not protein, and internal inconsistencies (abstract says 3 weeks, methods say 2). Tier B at most. No second independent source. Ceiling is yellow.

Counter-evidence held on record

Counter-evidence and confounding Authors list no pro-oxidant data; none was found. The study is a stress model, so the effect may reflect stress relief rather than a direct antioxidant action. The G6PD oxidant-hemolysis claim runs the opposite way and is addressed under Fails verification. Framing caution This is not evidence that chlorpheniramine is antioxidant in people and not a reason to expect or avoid any supplement. Do not recommend antioxidant supplementation or avoidance from this entry.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence supports even yellow, and no circulating copper claim for chlorpheniramine was traced (the reported metal-complex items are addressed under Fails verification as unsourced). This is a disclosed gap, not a finding of safety. Kept independent of Iron (Hard Rule 7). Gap type: mostly genuine, with some tooling limitation.

What was searched

PubMed listing "chlorpheniramine copper": 5 records, none human and none on copper status. Records were sheep hemodynamics with copper sulfate (chlorpheniramine as H1 probe), chromatography materials with copper as a structural component, a 1970 aortic strip study, and a copper phthalocyanine tracer study. Also DrugBank page (copper not mentioned) and the OTC labels.

Channel outcomes

PubMed listing: opened once for copper; related listings for iron and zinc opened. OpenAlex works search and Crossref title search: 429. Europe PMC: 429. WebSearch: budget exhausted. Repair retry: a PubMed listing combining chlorpheniramine with ferritin, serum iron, ceruloplasmin, serum copper, iron or copper absorption and hemoglobin returned a page with no matching records (only a trending block). Crossref (once opened for microbiome) and Europe PMC (once opened for mitochondria) did not address copper; later Europe PMC, Crossref and OpenAlex calls were 429. Mixed: clean zeros on PubMed phrasings, plus tooling-limited coverage of other channels.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C source, and no circulating iron claim for chlorpheniramine was traced. Not a finding of safety. The hemolysis case reports are filed under Oxygen delivery/utilization and share no iron measurement (see Overlap map). Gap type: genuine on the channel opened, partly tooling-limited.

What was searched

PubMed listing "chlorpheniramine iron": 9 records. None measured iron absorption, ferritin or anemia as an effect of chlorpheniramine. Chlorpheniramine appeared as premedication before parenteral iron (iron dextran), in an iron-chelator anaphylaxis case, and as a model drug in iron-crosslinked bead formulations. DrugBank (gated) and the OTC labels show no iron statement.

Channel outcomes

PubMed listing opened. OpenAlex search, Crossref, Europe PMC, PubChem and WebSearch: 429, refused, or exhausted. Repair retry: the combined ferritin, serum iron, iron absorption and hemoglobin PubMed listing returned no matching records. A methemoglobin query errored, and other channels were 429. Mixed: clean zeros on PubMed phrasings, with other phrasings untested because of throttling.

Limits on what this shows

• Null findings: A Cureus 2021 pilot trial of intranasal chlorpheniramine with xylitol (PMID 33816038) mentions microbiome modulation only as a hypothesis and measured none [22]. The Maier 2018 Nature gut-bacteria drug screen [16]: the article page was opened on repair and the visible text names no antihistamine, but the supplementary compound table could not be opened (Supplementary Information file refused by the site robots rule; PMC returned a bot check), so whether chlorpheniramine was screened is still unknown. Earlier PubMed "chlorpheniramine gut microbiota" returned no records.
• At-risk subgroups: None identified.

Direction

Possible composition shift in a non-gut bacterial community. Direction for the human gut is unknown, and this is not a nutrient finding.

Regulatory status

Not mentioned in the OTC labels [1][2].

Population evidence

Li et al. 2025 [21], J Hazard Mater 495:139028 (DOI 10.1016/j.jhazmat.2025.139028): microcosm and metagenomic study of seven antiallergic drugs in surface water (OpenAlex keywords name chlorpheniramine, diphenhydramine, cetirizine, loratadine and desloratadine). The PubMed abstract excerpt states the drugs increased antibiotic-resistant bacteria by 1.24 to 7.78 fold and that chlorpheniramine promoted Actinobacteria (for example Aurantimicrobium). The OpenAlex record has no abstract and no full text, so per-drug fold changes, exposure concentrations and replicate numbers were not retrieved. Chlorpheniramine was in the exposure set; the bacteria are from water, not from human stool.

Cohort test

Chlorpheniramine was a named exposure (Tier B, in vitro microbial study with this drug). The system is environmental, so it supports only the existence of an effect on bacterial communities and not any gut effect.

Mechanism

None named in the text retrieved. No gut-specific mechanism located.

Hunt result (red/orange)

Needed: a gut-bacteria screen or fecal 16S study naming chlorpheniramine, and a second independent source. Not found. Ceiling is yellow.

Counter-evidence held on record

Counter-evidence and confounding Environmental exposure concentrations may bear no relation to colonic exposure, and surface-water taxa differ from gut taxa. The only abstract excerpt came from a PubMed listing, with the full text closed. Framing caution Not evidence that chlorpheniramine disrupts the human gut microbiome. Do not recommend probiotics or other supplements from this entry.

Limits on what this shows

• Null findings: The Wikipedia G6PD page opened names no antihistamine among triggers [14]. A PubMed listing for "chlorpheniramine hemolysis G6PD methemoglobin" returned only generic methemoglobinemia and hemolysis papers, none naming chlorpheniramine as a cause. A dedicated "chlorpheniramine methemoglobinemia" query and a "chlorpheniramine G6PD" query were blocked (429) or returned 404, so methemoglobin and G6PD are tooling-limited, not closed. Repair retries of "chlorpheniramine methemoglobinemia" returned a fetch error and remain unresolved.
• At-risk subgroups: Not defined by the evidence.

Direction

Possible reduction in red-cell mass through immune hemolysis. This is a drug adverse event (outcome), not a nutrient deficiency (Hard Rule 2).

Regulatory status

No hemolysis, anemia or methemoglobin statement in the OTC labels [1][2].

Population evidence

Duran-Suarez 1981 [13], Br J Haematol, "The I antigen as an immune complex receptor in a case of haemolytic anaemia induced by an antihistaminic agent": a short report whose OpenAlex record has no abstract; MeSH indexing lists chlorpheniramine under adverse effects. A second record, Duran-Suarez et al., Vox Sanguinis 1981;41:313-315 (PMID 7324446), red cell I antigen as immune complex receptor in drug-induced hemolytic anemias, was opened on repair through its OpenAlex record: its abstract reports laboratory review of six patients with drug-induced hemolytic anemia, with immune complexes attaching to red cells only when I antigen was present in five of the six. Its MeSH adverse-effects terms list chlorpheniramine alongside nitrofurantoin, rifampin and streptomycin, and the abstract text does not name chlorpheniramine, so which patient (if any) took it and the count are unknown. No hemoglobin value or drug-dependent antibody result for chlorpheniramine was retrieved for either record. A direct PubMed single-record fetch for both PMIDs was refused (429, do not retry).

Mechanism

Immune complex mechanism implied by the titles. This is not the oxidant mechanism of G6PD deficiency.

Hunt result (red/orange)

Needed: abstract or full text of the two 1981 papers, case counts, and an independent cohort measuring hemoglobin or hemolysis markers in chlorpheniramine users. None obtainable. Ceiling stays yellow.

Counter-evidence held on record

Counter-evidence and confounding Case reports of drug-induced immune hemolysis exist for many drugs and are rare events. Whether the agent in the first report was chlorpheniramine is inferred from indexing by the fetch tool, not seen in text. A transfusion-premedication trial (PMID 30364108) used chlorpheniramine in thalassemia with no hemolysis finding attributed to it, which is context only. Framing caution This is a rare adverse-event signal, not an oxygen-carrying deficiency and not a G6PD warning. Do not state that chlorpheniramine lowers oxygen delivery. Kept independent of the ATP production entry (Hard Rule 7).

Limits on what this shows

• Null findings: PubMed "chlorpheniramine adenosine triphosphate" returned 6 records, all using chlorpheniramine as an H1 blocker in signalling work with no ATP content measured. A Europe PMC search for chlorpheniramine with mitochondria, ATP or oxygen consumption (15 records shown) surfaced no study measuring ATP or respiration under chlorpheniramine exposure; a "histamine enhances ATP-induced itching" record does not involve chlorpheniramine. Two further PubMed phrasings (a quoted-phrase ATP query and "chlorpheniramine mitochondrial membrane potential") returned the home page or a fetch error, so they are tooling-limited and unresolved.
• At-risk subgroups: Acute overdose exposure only. None identified for therapeutic use.

Direction

Hypothesized cellular energy depletion in acute overdose, on the consumption side rather than a production deficit. Drug toxicity and a clinical outcome, not a nutrient deficiency (Hard Rule 2).

Regulatory status

The OTC labels opened carry no muscle injury or energy statement [1][2].

Population evidence

Lu and Wu 2026 [20], Front Pharmacol 17 (DOI 10.3389/fphar.2026.1770052; PMID 41800096), single case: a 14-year-old female who ingested 100 tablets of 4 mg (400 mg). Creatine kinase peaked at 11,219 U/L on day 1; myoglobin was raised at 6 hours then fell; troponin, CK-MB, creatinine and uric acid stayed normal; serum potassium in the case table was 3.08 to 3.73 mmol/L. She recovered with gastrointestinal decontamination, diuresis and electrolyte management. No comparator, no ATP or mitochondrial measurement. Read through the Europe PMC record and the Frontiers full text via a summarizing fetch tool.

Mechanism

The authors hypothesize altered membrane permeability, Na+/K+-ATPase activation with "excessive intracellular ATP consumption", rising intracellular sodium and calcium, protease activation, myofibril overcontraction and energy depletion, and state the exact mechanism is not fully understood. Mitochondria are not mentioned. This is an untested hypothesis.

Hunt result (red/orange)

Needed: a measured ATP or respiration endpoint, and a second independent report. The case report cites earlier chlorpheniramine rhabdomyolysis cases (not opened), and the summarizer flagged that two cited reference titles did not clearly match the claims. Ceiling is yellow.

Counter-evidence held on record

Counter-evidence and confounding A single overdose case in an adolescent, with whether other causes of rhabdomyolysis or co-ingestants were excluded not retrieved. The mechanism is the authors' hypothesis, not a measured result. The yeast respiration study [10] is held under Mitochondrial burden and is not an ATP measurement. Framing caution Not an ATP-production deficiency and not a therapeutic-dose finding. Do not suggest energy or mitochondrial supplements from this entry. Kept independent of Mitochondrial burden and Oxygen delivery/utilization (Hard Rule 7).