Levocetirizine

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence and no circulating mitochondrial claim found (the only "energy" claim is fatigue, rebutted under Fails verification). Disclosed gap. Re-check when PubMed access is stable.

What was searched

Web search "levocetirizine mitochondria OR 'oxygen consumption' OR ATP OR 'membrane potential' in vitro cells" (generic membrane-potential methods papers); "cetirizine mitochondrial toxicity OR 'mitochondrial function' OR 'complex I' OR 'ATP depletion' antihistamine second-generation" (patents and unrelated toxicology; the one antihistamine hit was the cetirizine mouse liver study, which reported MDA and GSH, not mitochondrial or ATP markers [14]). Nature 2018 gut-bacteria drug screen opened; it names no antihistamine in the text read [16]. The cyclophosphamide and LPS rat studies measured redox markers only [8][9].

Channel outcomes

A final PubMed listing for levocetirizine with mitochondria, oxidative stress, ATP or microbiome terms returned 429 twice (spaced), and a matching Crossref listing was also 429-limited, so that sweep was not completed. Tooling-limited as well as a likely true gap. Repair attempt 2026-10-08: two further Crossref title queries (levocetirizine with mitochondrial function and oxygen consumption; levocetirizine with mitochondrial toxicity and ATP) and one on membrane potential were rate-limited (429) and returned nothing usable; the proxy asked that those pages not be fetched again, so no further attempts were made. The supplementary content of the Nature screen could not be opened (see Gut microbiome risk). Result: no new evidence; the earlier null channels stand and the sweep remains incomplete.

Limits on what this shows

• Null findings: GSH was not restored by levocetirizine in the LPS model [8]. No human oxidative-stress study of levocetirizine users was located [18][19][25].

Direction

Reverse (apparent antioxidant effect in injury models). Not a depletion. Not evidence of benefit in people.

Regulatory status

Not mentioned in the US label or SmPC sections retrieved [1][3]. The SmPC states preclinical safety data revealed no special hazard [3].

Population evidence

No human data. Fahmi 2018 [8]: male Sprague-Dawley rats, n = 6 per group, levocetirizine 1 mg/kg/day orally for 1 week then LPS 7.5 mg/kg intraperitoneally. LPS raised lung MDA (p < 0.01) and lowered lung SOD (p < 0.001) and GSH (p < 0.0001); levocetirizine "abolished" the MDA and SOD changes (no p value, no means given), did not alter GSH, and attenuated BALF NOx (p < 0.01). El-Kashef 2023 [9]: rats, n = 10 per group, levocetirizine 1 mg/kg for 14 days with cyclophosphamide 150 mg/kg on day 7. Cyclophosphamide raised lung MDA and NOx and lowered GSH and SOD; levocetirizine reversed these changes qualitatively (values are in figures I did not read; catalase not measured).

Mechanism

Not established. Fahmi's authors list H1 blockade, ROS scavenging, SOD activation, thioredoxin and reduced cell infiltration as possibilities and state mechanisms were not addressed [8].

Class cohort test

Both rat studies used levocetirizine itself (Tier B). Opposing racemate signal, cetirizine (not levocetirizine) in cohort: a mouse study of chlorpheniramine and cetirizine liver injury reported that L-carnitine lowered hepatic MDA and raised GSH [14], which implies antihistamine-associated hepatic oxidative changes, but dose, the cetirizine-alone values and the exact comparison were not visible in the page text read, so it is not weighted. Class extrapolation only.

Counter-evidence held on record

Counter-evidence and confounding Pretreatment in injury models says nothing about healthy people. Two independent groups used the same 1 mg/kg dose, so agreement is not independent confirmation of a human effect. Tissue and species differences apply. Framing caution Do not present levocetirizine as an antioxidant or as protective. Do not recommend any antioxidant supplement from this entry.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C source for levocetirizine and iron, and no circulating iron claim located. Genuine gap with a partial tooling limit. Not reassurance.

What was searched

Web search "cetirizine OR levocetirizine hemoglobin anemia iron deficiency antihistamine cohort" (bioequivalence trial, label pages, a childhood rhinitis trial title; none measured iron); "levocetirizine iron OR ferritin OR serum iron OR copper OR ceruloplasmin study" (unrelated iron and ceruloplasmin physiology papers); the PubMed and Crossref queries described under Zinc [23][24]. Labels list no iron interaction and no acid-suppression or chelation mechanism [1][3].

Channel outcomes

The acid-suppression to iron and B12 literature belongs to H2 receptor antagonists and PPIs, not to H1 antihistamines; a pharmacist review I opened discusses H2RAs only and does not list H1 antihistamines [22]. Not borrowed. The EPAAC hematology null is not iron-specific [5]. Tooling: later PubMed listings were rate-limited (429) and PMC returned bot-verification; WebSearch budget ran out.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C evidence, no circulating copper claim. Disclosed gap, not safety.

What was searched

The combined iron and copper web query above (ceruloplasmin included); the PubMed and Crossref metal queries [23][24]; "cetirizine zinc complex OR chelation OR serum zinc OR copper antihistamine study", which returned titles on metal chemistry and on zinc and copper status in asthma and atopic disease (disease association, not drug; titles only) with no levocetirizine data. Kept separate from Iron (Hard Rule 7).

Channel outcomes

No copper statement in the labels read [1][3]. No in vitro copper chelation study of levocetirizine was located. Same tooling limits as Iron.

Limits on what this shows

• Why no grade: Dual condition judged met: neither study provides Tier B or C evidence that levocetirizine changes the microbiome (one is non-attributable, one is silent on this drug), and no circulating microbiome claim for levocetirizine was found. The responder-versus-control null is disclosed but is not treated as safety evidence. Disclosed gap, partly tooling-limited.

What was searched

Web search "levocetirizine gut microbiota OR microbiome OR dysbiosis antihistamine 16S"; Nature 2018 drug-by-bacteria screen [16]. Frontiers 2022 [10] (Song, Dan, Yao, Yang, Chen, Hao; authors confirmed by a Crossref single-DOI lookup and the Frontiers page, 2026-10-08), levocetirizine IN the cohort: case-control, tertiary hospital in Chongqing, 16S rRNA; antihistamine-free patients received levocetirizine 5 mg/day for 2 weeks and were classed as resistant (RCSU, n = 25) or responders (CSU, n = 19) and compared with healthy controls (n = 19). Responders versus controls: no difference in Shannon diversity (p = 0.478) or genus abundance. Resistant versus responders: lower Shannon (2.88 plus or minus 0.56 versus 3.47 plus or minus 0.56, p = 0.001; healthy controls 3.27 plus or minus 0.81) and higher Escherichia (1.16 plus or minus 1.85 versus 0.11 plus or minus 0.25, corrected p < 0.001, the only genus surviving correction); Blautia, Anaerostipes, Alistipes and Lachnospira were lower and Prevotella and Megamonas higher in the resistant group at uncorrected p < 0.05 or < 0.01.

Channel outcomes

The groups were defined by response to the drug, there was no pre-treatment sample and no untreated urticaria group, and the authors list absent before-and-after sampling as a limitation [10]; differences therefore reflect disease or response phenotype, not a measured drug effect. The Nature screen (more than 1,000 drugs, 40 strains, about 24% of human-targeted drugs inhibited at least one strain) names no antihistamine in the text read, and its supplementary table was not accessible, so whether levocetirizine was screened is unknown [16]. Repair attempt 2026-10-08: the Nature article page was opened again and its only supplementary link (Supplementary Table 1) is described there as the pharmacokinetic estimates behind Extended Data Fig. 3, not a full drug list; a direct fetch of the Springer static supplementary spreadsheet was refused by robots.txt and was not worked around. A Crossref query for levocetirizine with gut microbiota or dysbiosis returned eight unrelated records (COVID-19, antibiotics, bile acids, acne), none on levocetirizine. In the Frontiers study the authors state that gut flora was not assessed before and after antihistamine treatment, that there was no within-subject verification, and that other second-generation agents were not included [10]. Europe PMC and PubMed listings were rate-limited. Genuine gap for any drug-attributable change; tooling-limited for the Nature drug list.

Limits on what this shows

• Null findings: No ATP, respiration or membrane potential study of levocetirizine was located (see Mitochondrial burden). The sedation battery was null for levocetirizine [7][15].

Direction

Increased regional glucose utilization (higher demand), not impaired ATP production. Hard Rule 2: a drug's CNS pharmacodynamic effect is not an ATP deficiency.

Regulatory status

Not mentioned in the labels retrieved [1][3].

Population evidence

Kikuchi 2018 [7]: double-blind, placebo-controlled, three-way crossover, 18 healthy young Japanese men, single doses of levocetirizine 5 mg and diphenhydramine 50 mg at least 6 days apart; FDG-PET and near-infrared spectroscopy during word fluency, two-back and Stroop tasks. Abstract: prefrontal energy consumption rose after antihistamines, most with diphenhydramine. The abstract gives no effect sizes, p values or regions for levocetirizine alone. Full text was not retrievable (publisher page 403), though the abstract was read in two independent records (Crossref and OpenAlex). Repair attempt 2026-10-08: a PubMed single-record lookup (PMID 29532516) returned only the abstract, now with PMC ID PMC5900896; the PMC page returned a reCAPTCHA verification page, the Wiley direct PDF returned 403 (OpenAlex lists it as hybrid open access), and the Europe PMC copy is blocked to the fetch tool by robots.txt. No route around these was attempted, so the FDG and NIRS effect sizes remain unretrieved and the entry stays yellow (Tier A single-dose surrogate, not an ATP measurement, so it could not reach orange even with the numbers).

Mechanism

The authors propose higher energy demand with reduced capillary permeability, a hypothesis that needs validation [7]. No mitochondrial or ATP measure exists.

Counter-evidence held on record

Counter-evidence and confounding Single dose, healthy men, regional brain measure, n = 18. The signal was largest for the sedating comparator. Not extrapolable to systemic energy metabolism. Framing caution Not a "low energy" or ATP-depletion claim. Fatigue on the label is a central H1 effect, not evidence of impaired cellular energy production.

Direction

Possible reduced red-cell mass through rare idiosyncratic hemolysis. Hemolytic anemia is a clinical outcome and is not iron deficiency (Hard Rule 2).

Regulatory status

Levocetirizine: the UK SmPC postmarketing list contains no blood or lymphatic disorders [3]; the US label postmarketing summary I read does not list a hematologic category [1]. Cetirizine: the Canadian monograph lists "hemolytic anemia, thrombocytopenia" among rare, potentially severe postmarketing events, with no counts [13].

Population evidence

EPAAC [5]: hematology and biochemistry changes were similar in the levocetirizine and placebo arms (514 children, 18 months) and none were clinically significant; no numeric values in the document read. Kikuchi 2018 [7]: prefrontal oxygenated hemoglobin by near-infrared spectroscopy was lower with diphenhydramine; the abstract does not report a levocetirizine reduction, and this is a regional cerebral measure, not blood oxygen-carrying capacity.

Mechanism

Absent for levocetirizine. No oxidant, methemoglobin-forming or marrow-suppressing chemistry is described for it in any source retrieved.

Class cohort test

CLASS EXTRAPOLATION (racemate). Levocetirizine was NOT in the cohort behind the cetirizine monograph wording [13] (it describes cetirizine postmarketing reports). Capped at yellow. The parallel cetirizine dossier was not opened.

Counter-evidence held on record

Counter-evidence and confounding The levocetirizine SmPC does not carry the wording, and the pediatric trial hematology was unremarkable [3][5]. Spontaneous postmarketing reports cannot establish causation or frequency. Framing caution This is not an oxygen-delivery or anemia claim for levocetirizine. It marks a rare idiosyncratic label term seen on the racemate.