Cetirizine

Limits on what this shows

• Null findings: No human or intact-mammal mitochondrial measurement was found.
• At-risk subgroups: None established.

Direction

Burden (harm) at high in vitro concentration. A drug effect on an organelle, not a nutrient finding.

Regulatory status

No label read mentions mitochondrial effects [1][2][3].

Population evidence

Tier B: Salimi et al. 2018 [5], cetirizine at 4 to 40 ug/mL in human blood lymphocytes caused mitochondrial membrane potential collapse (no numbers in the abstract). A PubMed search for cetirizine and mitochondrial returned 4 records; the other three concern a platinum(IV) complex, a Leishmania screen (no effect) and a Leber hereditary optic neuropathy case report implicating erythromycin, not cetirizine [23]. Environmental exposure studies in mussels report an electron transport system measure (listing-level gist; not used) [22].

Mechanism

Present in vitro only: loss of membrane potential in exposed lymphocytes. Not shown at therapeutic concentration.

Counter-evidence held on record

Counter-evidence and confounding The lowest effective concentration is about 6-fold above the label pediatric Cmax (adult Cmax was not retrieved). A single abstract-level study cannot support a clinical claim. Framing caution Not a deficiency claim and not a reason to take mitochondrial supplements. This entry shares its only source with Oxidative stress and ATP production (see Overlap map).

Limits on what this shows

• Null findings: A non-mammalian ecotoxicology literature (mussel and clam exposures, PMIDs 28273617 and 28578237) reports mixed redox responses, with little oxidative injury in clams at low doses (listing-level gist; not used for grading) [22]. No human study measured MDA, 8-isoprostane, GSH or antioxidant enzymes during cetirizine treatment.
• At-risk subgroups: None established.

Direction

Mixed: pro-oxidant at supratherapeutic in vitro concentrations, anti-oxidant (reverse direction) in eosinophils. Hard Rule 2: this is a redox marker finding, not a nutrient deficiency, and it does not imply antioxidant supplementation.

Regulatory status

No label read mentions oxidative stress or antioxidant status [1][2][3].

Population evidence

Tier B, pro-oxidant: Salimi, Razian, Pourahmad, Curr Clin Pharmacol 2018, human blood lymphocytes in vitro. Buspirone and cetirizine were more toxic than olanzapine; cetirizine at 4, 20 and 40 ug/mL was associated with significant ROS formation, mitochondrial membrane potential collapse, lipid peroxidation, lysosomal damage and raised GSSG. The abstract gives no numerical values and an IC50 of 200 ug/mL at 6 hours whose drug is unclear [5]. For scale, the pediatric Cmax in the label was 660 ng/mL (0.66 ug/mL) at a 5 mg dose in ages 2 to 5 [2], so the lowest effective concentration was about 6 times that value (adult Cmax was not retrieved). Tier B, anti-oxidant: Okada et al., Int Arch Allergy Immunol 1994, human eosinophils in vitro at 0.01 to 1 ug/mL; cetirizine inhibited superoxide generation 60 minutes after platelet-activating-factor activation in allergic subjects, with no significant inhibition in normal subjects; subject numbers and superoxide percentages are not in the abstract [6]. A 1996 J Asthma study (PMID 8968296) reported decreased superoxide from integrin-dependent eosinophil burst only at 250 ug/mL and only transiently (listing-level gist, abstract not opened) [7]. Tier B, animal: a mouse study of chlorpheniramine and cetirizine reported that L-carnitine co-treatment lowered hepatic MDA and raised hepatic GSH versus the antihistamine-only groups, with no numbers or doses in the page read [9]. A 2025 rat study reports cetirizine reduced placental MDA and increased GSH and total antioxidant capacity in a cyclophosphamide model (listing-level gist; abstract unavailable) [10].

Mechanism

Named for the pro-oxidant arm: mitochondrial membrane potential collapse and glutathione oxidation in vitro [5]. Mechanism for the anti-oxidant arm is inhibition of eosinophil respiratory burst [6][7]. Neither is tied to a nutrient.

Counter-evidence held on record

Counter-evidence and confounding The pro-oxidant arm used concentrations far above therapeutic exposure; the anti-oxidant arm used concentrations near it but only in isolated cells. The two directions cannot be summed into a net clinical effect. The animal protection studies used disease models in which cetirizine is compared against injury, not against untreated animals. Framing caution Not a deficiency claim. No antioxidant supplement is implied or recommended.

Limits on what this shows

• Null findings: No study measured serum copper or ceruloplasmin with cetirizine exposure.
• At-risk subgroups: None established.

Direction

Neutral or unknown.

Regulatory status

No label read mentions copper [1][2][3].

Population evidence

Tier B: the same Chem Biodivers 2024 study [11] reports that the Cu(II) complex had the highest antibacterial activity among the complexes and, with the Zn(II) complex, increased lipoprotein lipase activity and lowered triglycerides in high-fat-diet mice, unlike the Cd(II) complex; serum copper was not reported. A PubMed search for cetirizine and copper returned 3 records; the other two (a pediatric syrup erosion study using copper as a sugar-assay reagent and an immobilized-laccase review) concern no biological copper [32].

Mechanism

Present only as laboratory complexation. No transporter competition, ceruloplasmin or enzyme data exist for cetirizine in any source retrieved.

Counter-evidence held on record

Counter-evidence and confounding As for zinc: a synthetic complex is not an in vivo interaction. Copper is kept separate from Iron and from Zinc per Hard Rule 7, but the zinc and copper entries rest on the same single paper (see Overlap map). Framing caution Not a deficiency claim and not a reason to supplement copper.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence supports even a yellow grade, and no circulating iron claim for cetirizine was found after the consumer sweep. This is a disclosed gap, not a finding of safety. Kept independent of Copper and Oxygen delivery/utilization (Hard Rules 7 and 9). Re-check if a cetirizine-stratified cohort with ferritin or hemoglobin is published.

What was searched

PubMed listing "cetirizine iron" (7 records): in vitro cetirizine-diclofenac complexes including Fe(III), an iron-graphene water-treatment sorbent, an iron-chelator (desferrioxamine) mast cell activation study in which cetirizine reduced skin reactions, the congenital methemoglobinemia case, an aquifer recharge field study, an anagrelide case report with iron tablets as a co-medication, and heme-iron P450 ligand work on histamine displacement. None measured iron status with cetirizine exposure [25]. Labels read [1][2][3] mention no iron, and neither does the Australian Product Information [40] or the Spanish oral solution leaflet [41]. The methemoglobin cases are handled under Oxygen delivery/utilization. Repair pass 2026-10-08: PubMed listing "cetirizine ferritin OR cetirizine anemia OR cetirizine hemoglobin" (12 records) held no study measuring iron status or ferritin in cetirizine users; ferritin appeared only in a COVID-19 renin-angiotensin paper in which cetirizine was an indexing term [44]. Consumer-claim sweep: WebSearch phrasings on cetirizine/Zyrtec with iron, ferritin, anemia, hair loss and "nutrient depletion list" were run and the pages opened (a nursing drug-reference excerpt that covers both cetirizine and iron, a nutrient-depletion blog, a trade magazine article, a retail health site, a supplement magazine and a Substack table) contained no statement linking cetirizine or Zyrtec to iron [42][43]. Histamine-2 blocker and proton pump inhibitor iron-deficiency literature turned up in a search on antihistamine-iron absorption; it concerns gastric acid suppression, which H1 blockade does not cause, so it was not treated as class evidence for cetirizine.

Channel outcomes

PubMed listings (two): opened. WebSearch (now available): five iron and depletion-list phrasings run, seven consumer or reference pages opened. PMC article pages: reCAPTCHA. Result: a clean zero on both PubMed listings and a clean zero in the consumer-claim sweep. This now looks like a genuine literature gap for the drug-to-iron direction rather than a tooling limit, although no cetirizine exposure cohort with ferritin exists to confirm absence.

Limits on what this shows

• Null findings: No significant antihistamine class enrichment in the Maier screen after multiple-testing correction [34]. Opposite directions within the class [33]. No human exposed-versus-unexposed microbiome contrast for cetirizine was found. Access: the Maier supplementary tables (Supplementary Table 1 xlsx is blocked to the fetch tool by robots.txt) and PMC article pages PMC11732700, PMC8967245, PMC6969170 and PMC12542764 were bot-challenged and not read; the 2025 CSU paper was read through its DOAJ abstract only.
• At-risk subgroups: None established.

Direction

Unknown for cetirizine; mixed within the class (inhibition with cyproheptadine and desloratadine, promotion with fexofenadine). A microbiome composition or function change, not a nutrient finding, and not a reason to take a probiotic.

Regulatory status

No label read mentions a microbiome effect; the labels were read for pharmacokinetic, adverse-event and interaction text and no microbiome statement was seen [1][2][3].

Class cohort test

CLASS EXTRAPOLATION. Hammouda, Wasfi and Abdeltawab, BMC Microbiol 2025: fexofenadine HCl, cyproheptadine HCl and desloratadine, tested at "intestinal concentrations" (values not given on the page read) against four reference strains (Bifidobacterium longum, Limosilactobacillus reuteri, Bacteroides fragilis, Escherichia coli); cetirizine and every piperazine antihistamine were not tested. Maier et al., Nature 2018: 1,197 drugs against 40 gut isolates; cetirizine and its ATC subgroup R06AE are not named anywhere in the text read, and whether cetirizine was in the screen is unconfirmed because the supplementary table could not be opened. Cetirizine is therefore not documented in either cohort. Capped at yellow [33][34].

Population evidence

Tier C, in vitro: cyproheptadine and desloratadine inhibited the growth of all four strains and reduced biofilm formation and altered adherence to Caco-2/HT-29 cells; fexofenadine promoted growth of all species except B. longum, enhanced biofilm and adherence of B. longum and L. reuteri, and raised lactic, propionic and acetic acid (acetic acid p under 0.05); no effect sizes or confidence intervals were on the page read, and the full text was not opened [33]. Tier C, screen: in Maier 2018 the extended-data captions say "phenothiazine and other antihistamines (R06AD and R06AX) are enriched" but that this does not hold after multiple-testing correction given small numbers, and the main text names only antimetabolites, antipsychotics and calcium-channel blockers as significantly enriched subclasses [34]. Human data that mention antihistamines contain no exposed-versus-unexposed contrast: Song 2022 (63 participants, all patients on levocetirizine, no drug-free comparator) [12]; and a 2025 Clin Transl Allergy case-control study of 20 chronic spontaneous urticaria patients with uncontrolled symptoms on second-generation antihistamines (drug not named) versus 15 healthy controls, which found higher diversity and a higher Firmicutes/Bacteroides ratio in patients and no association with treatment type, and which cannot separate disease from drug [35]. A PubMed listing for cetirizine and microbiota (4 records) held no cetirizine-exposure microbiome contrast [26]. An Estonian cohort preprint text read did not mention antihistamines [14].

Mechanism

Not named for cetirizine. For the tested class members the study measured growth, biofilm, adherence and short-chain fatty acid output, not a mechanism; whether cetirizine reaches the colon at inhibitory concentrations was not examined.

Counter-evidence held on record

Counter-evidence and confounding The three tested drugs are different molecules and pointed in opposite directions, so the class result does not predict the direction for a fourth drug; in vitro growth of four reference strains does not predict community change in people, and allergic disease itself changes the microbiome. This entry shares no source with any other entry except the human background papers listed in the Overlap map. Framing caution Not a deficiency claim and not a reason to take a probiotic or change diet. A class-level signal for other drugs is not evidence about cetirizine.

Limits on what this shows

• Null findings: No direct ATP, respiration or oxidative phosphorylation measurement with cetirizine was found.
• At-risk subgroups: None established.

Direction

Theoretical reduction at high in vitro concentration. A drug effect on cellular energetics, not a nutrient finding.

Regulatory status

No label read mentions cellular energy [1][2][3].

Population evidence

The only adjacent evidence is the lymphocyte membrane potential result [5]; ATP content was not reported in the abstract. A PubMed search for "cetirizine ATP" returned 16 results; the 10 shown concern pharmacokinetic modeling, efflux transporters (ATP-binding cassette), mast cell signaling and mouse hepatic steatosis, none showing a change in cellular ATP, respiration or energy metabolism [27]. The mouse steatosis study [8] did not report ATP.

Mechanism

Inferred, not demonstrated: membrane potential is the driving force of ATP synthase.

Counter-evidence held on record

Counter-evidence and confounding The inference chain (membrane potential to ATP) is untested here and the exposure is supratherapeutic. Kept as its own entry per Hard Rule 7 even though it shares the single source with Mitochondrial burden; do not count the two as independent confirmation. Framing caution Not a "low energy" claim. Fatigue on the label (6%) is an adverse event of the drug and has no demonstrated link to ATP.

Limits on what this shows

• Null findings: No hemoglobin or hematocrit change was documented in any cetirizine source retrieved. The 2026 methemoglobin case [15] is a negative for cetirizine causation. A PubMed listing for cetirizine with ferritin, anemia or hemoglobin (12 records) held no cohort or trial measuring hemoglobin in cetirizine users: the hits were case reports in which cetirizine was a co-medication, an assay interference study, and the two methemoglobinemia cases [44]. Three spontaneous-report analyses of cetirizine were opened; two were limited to nervous system or neuropsychiatric terms and gave no hemolysis, anemia or methemoglobin figures, and the third (Kong 2024, FAERS) was available only as an abstract [39].
• At-risk subgroups: None established.

Direction

Possible reduction in red-cell mass through hemolysis (an adverse event), and, in one overdose case, reduced oxygen-carrying capacity through methemoglobin formation (a drug toxicity). Hard Rule 2: anemia and methemoglobinemia are outcomes, not iron or B12 deficiency, and no nutrient is implicated.

Regulatory status

Health Canada monograph: "hemolytic anemia, thrombocytopenia, orofacial dyskinesia, severe hypotension, anaphylaxis, hepatitis" listed as rare postmarketing events [3]. US syrup label (via aggregator summary): hemolytic anemia, thrombocytopenia and hepatitis listed as additional rare but potentially severe events [2]. The IV label (Quzyttir) reports no hematologic events in the text read [1]. The Australian Product Information (Alzene, revised 11/09/2024) also lists haemolytic anaemia among rare, potentially severe postmarketing events [40]. The Spanish Zyrtec oral solution leaflet lists very rare thrombocytopenia and no anemia or hemolysis [41]. Frequencies are not given.

Population evidence

No cohort or trial with hemoglobin as an outcome. A PubMed search for "cetirizine hemolytic" returned 2 records: a ceftriaxone-induced immune hemolytic anemia case report in which cetirizine was only symptomatic treatment, and a levocetirizine assay paper stating "hemolytic effect was negligible" (an in vitro assay validation point, not a clinical finding) [24]. Tier B, single case: BMJ Case Rep 2026, a woman in her 70s with COPD and persistent hypoxia (SpO2 86%) had methemoglobin 26.5%; she took cetirizine and indapamide, but genetic testing showed a homozygous cytochrome b5 reductase variant (type 1 congenital methemoglobinemia) and the abstract attributes the case to the congenital deficiency, not to cetirizine [15]. Tier B, single case that does implicate cetirizine: Grillo et al., J Pediatr Pharmacol Ther 2019, an 18-year-old woman (42.18 kg) who ingested 2 tablets of 20 mg plus 10 to 16 tablets of 10 mg within about an hour (estimated 120 to 180 mg, roughly 12 to 18 times a 10 mg dose) developed methemoglobin 38% on arterial blood gas, SaO2 94% on room air on arrival falling to 85% forehead and 75% on the left hand with cyanosis unresponsive to 100% oxygen. After IV methylene blue (second dose 4 hours later) methemoglobin fell to 22% at 1 hour and 3.3% at discharge; hemoglobin was not reported ("hematological profile was unremarkable"). The authors state this is the first report of cetirizine as a cause, found no Naranjo or other formal causality assessment (causality was concluded "in the absence of any other triggering factor"), noted a history of recurrent, spontaneously resolving blue-hand episodes, noted that baseline methemoglobin "remained slightly high", and recorded that she declined full enzyme testing, so a congenital reductase deficiency was not excluded. No comparator, no cohort, no confidence interval [36].

Mechanism

Not named in the label text read. Drug-induced immune hemolysis is a recognized general mechanism but no cetirizine-specific mechanism was retrieved. For methemoglobinemia the case authors speculate that oxidative metabolism of a very large dose may generate reactive by-products such as superoxide or hydrogen peroxide that overwhelm protective enzyme systems; this is stated as speculation and sits uneasily with the Australian Product Information statement that cetirizine is less extensively metabolised than other antihistamines [36][40].

Counter-evidence held on record

Counter-evidence and confounding Spontaneous postmarketing reports do not establish causation; concurrent drugs and infections confound hemolysis reports. This is the strongest-sounding entry in the dossier and still has no effect size. The overdose case cannot be generalized to ordinary use, a congenital methemoglobin reductase deficiency was not excluded in that patient, and a single uncontrolled case report is Tier B at most, so the entry stays yellow. Framing caution An adverse-event signal, not a nutrient deficiency, and not evidence that the drug reduces oxygen delivery in ordinary use. Do not recommend iron, B12 or vitamin C from this entry.