Azithromycin

Limits on what this shows

• Null findings: A 2025 MDPI respirometry study [18] tested permeabilized HEK293T cells with gentamicin, ciprofloxacin and amoxicillin only; azithromycin was not tested, so it is excluded as evidence. A 10-record PubMed search on mitoribosome and azithromycin returned structural reviews with no azithromycin experiments [26]. LiverTox could not be opened (bot challenge), so a hepatic mitochondrial mechanism was not checked.

Direction

Possible mitochondrial translation or biogenesis inhibition (mechanistic plausibility). Not a nutrient deficiency; hepatotoxicity is a drug toxicity and is not filed here.

Regulatory status

The label and the StatPearls chapter do not mention mitochondria; the label mechanism is bacterial 50S ribosome binding [1][3].

Population evidence (Tier B)

Lamb 2015 [15]: 12 cancer cell lines across 8 tumor types were used in the paper; azithromycin was the erythromycin-class representative and was tested in MCF7, T47D, DCIS.com and U-87 MG among others. Mammosphere formation in MCF7 was inhibited with an IC50 of about 50 micromolar (50 to 250 micromolar tested, 250 micromolar most effective, p under 0.001); oxygen consumption, ATP and mitochondrial mass were not reported for azithromycin and normal-fibroblast toxicity was tested only for other drugs (full text via summarizing fetch). Fiorillo 2019 [16]: 1 micromolar azithromycin with 1 micromolar doxycycline and 250 micromolar vitamin C in MCF7 inhibited cancer stem cell propagation by more than 90% (combination; see ATP). A 2023 MCF-7 hypoxia study [17] tested azithromycin and examined mitochondrial stress and membrane potential, with no numbers in the abstract and azithromycin unable to inhibit sphere formation in hypoxia (listing abstract only).

Plasma level comparison

The label peak plasma level after a 500 mg dose is 0.5 mcg/mL [1], about 0.67 micromolar (calculated here with a molecular weight of about 749 that is not from a source opened). The 50 to 250 micromolar in vitro range is roughly 75 to 370 times higher. The label states the drug penetrates many tissues [1]; tissue concentrations were not retrieved, so the gap in tissue is unquantified.

Mechanism

Proposed by the authors: the mitochondrial ribosome resembles the bacterial ribosome, so macrolides inhibit mitochondrial protein synthesis as an off-target effect [15][16]. Not shown for azithromycin by a direct respiration measurement in any source opened.

Counter-evidence held on record

Counter-evidence and confounding The Lisanti-laboratory papers [15][16] are one research group testing a drug-repurposing hypothesis in proliferating cancer lines; they are not independent confirmation and do not address normal tissue. Doses are supra-pharmacologic relative to plasma. Framing caution Do not state that azithromycin damages mitochondria in people or causes fatigue through energy failure. This is a laboratory hypothesis, graded for mechanistic plausibility only.

Limits on what this shows

• Null findings: No human study of malondialdehyde, glutathione or antioxidant capacity in azithromycin-treated people appeared in the top 10 PubMed records for the query (they were animal, algal or plant studies) [19][31].

Direction

Mixed (pro-oxidant at toxic doses, protective in inflammation or toxin models). This is a reverse-direction finding for part of the data and is not a deficiency.

Regulatory status

Not addressed in the label [1].

Population evidence (Tier B, animal; abstracts only)

Male Wistar rats given azithromycin 30 mg/kg for 21 days: malondialdehyde higher with azithromycin alone, reduced by co-treatment with gallic and glycyrrhetinic acids (Sci Rep 2025, PMID 40113827). Rats given 30 mg/kg/day for 2 weeks: oxidative markers changed and were ameliorated by rosuvastatin, direction not stated in the abstract (Life Sci 2021, PMID 33476632). Broilers at 50 to 200 mg/kg: malondialdehyde rose and SOD and catalase fell more at higher doses (Vet World 2024, PMID 39077436). In contrast, rats given acrylamide with azithromycin 3.1 to 50 mg/kg had lower malondialdehyde at all doses and higher GSH at 3.1 and 6.25 mg/kg (Neurotoxicology 2024, PMID 38043637), and Mycoplasma-infected mice treated with azithromycin had lower malondialdehyde and higher SOD and GSH via Nrf2/ARE (Cent Eur J Immunol 2025, PMID 41438358) [19]. Doses were 30 mg/kg in the rat toxicity studies against 10 mg/kg/day in children [6]; interspecies scaling was not applied, so human relevance is unquantified.

Mechanism

Pro-oxidant effects at high dose are described in the rodent organ-toxicity papers without a mechanism proven in the abstracts; anti-inflammatory and Nrf2-linked effects are described for the protective findings [19].

Counter-evidence held on record

Counter-evidence and confounding Animal doses, species and models differ widely, numeric values were not available in the abstracts, and the protective findings come from disease models in which the infection or toxin itself drives oxidative stress. Framing caution Do not claim that azithromycin causes oxidative stress or depletes antioxidants in people. If anything, part of the animal data point to an antioxidant effect.

Limits on what this shows

• Null findings: No human or animal copper measurement after azithromycin was found. The other 9 records in the copper search were environmental, synthetic-chemistry, analytical or materials papers [32]. The 9-record zinc listing measured no copper [31].

Direction

Possible binding of copper by the drug in vitro (mechanistic plausibility). Not a depletion and not merged with Iron (Hard Rule 7).

Regulatory status

The label names no copper interaction [1]; StatPearls and Wikipedia make no mineral statements [3][4].

Population evidence (Tier B, in vitro chemistry)

PMID 7695446, Antibiotiki i Khimioterapiia 1994 (title paraphrased by the fetch tool as interactions between copper ions and azalide, azithromycin): atomic absorption, IR and UV spectroscopy and potentiometry showed a 1:1 metal-ligand compound across molar ratios from 10:1 to 1:10, with a solubility product of 9.8 x 10^-14 at pH 7.0 [32]. Listing abstract only; authors, full text and the concentrations used were not retrieved.

Mechanism

In vitro complexation is shown in the abstract. Whether it occurs at relevant concentrations in the gut lumen, bile or blood, and whether it changes copper absorption or status, was not studied in anything retrieved. The label notes biliary excretion of unchanged drug [1].

Counter-evidence held on record

Counter-evidence and confounding A single abstract from a 1994 in vitro study; a stable complex in a test tube does not establish copper loss in a person. No replication was found. Framing caution Do not state that azithromycin lowers copper or causes copper deficiency. Do not suggest copper supplementation.

Limits on what this shows

• Why no grade: Dual condition met: no Tier B or C source on iron was retrieved and no circulating iron claim for azithromycin was found. This is a disclosed gap, not a finding of safety. Mixed genuine gap and tooling-limited.

What was searched

DailyMed Zithromax label [1]; StatPearls [3]; PubMed listing "azithromycin hemoglobin OR anemia OR haemolytic with trial or cohort" (76 results, top 10 read; hemoglobin outcomes only, no iron indices) [31]; PubMed listing "azithromycin zinc supplementation" (no ferritin or iron measured) [31]; PubMed listing "azithromycin induced hemolysis" (7 records, no human azithromycin hemolysis) [31]; PubMed listing "azithromycin ferritin OR iron chelation OR iron absorption" (10 of 50,004 records shown, none mentioning azithromycin; all iron or tetracycline reviews, so the Boolean OR made the query too broad to be informative) [31]; PubMed listing "azithromycin copper" (10 records; copper was studied in vitro or environmentally, none examined iron or zinc with azithromycin) [31][32]

Channel outcomes

Label, StatPearls and Wikipedia opened. Antidote Research (consumer depletion site) pages for azithromycin and Zithromax returned 404 and its amoxicillin page names no nutrient [30]. WebSearch had no budget left; PMC and several publisher pages were bot-blocked. A PubMed phrasing "azithromycin zinc iron copper serum levels patients" returned a 404. Hemoglobin outcomes that were found (null in randomised trials [20][21][22]) are filed under Oxygen delivery/utilization and are not iron measurements (Hard Rule 2, Hard Rule 7).

Limits on what this shows

• Null and opposite-direction findings: Gamma diversity not significantly altered in MORDOR I (p = 0.08) [8]; Shannon and overall composition unchanged in MORDOR Malawi [10]; Shannon not significant in Parker (p = 0.087) [5]; Wei found no composition difference at 13 to 39 months [6]. Abeles 2016 [11] (azithromycin and amoxicillin, one treated person per household, placebo to others, 6 months): in the OpenAlex abstract, gut dissimilarity over time was not sped up by antibiotic use compared with household members, while the authors conclude that as few as 3 days of either drug can cause sustained diversity reductions; the gut result is mixed and N was not retrieved. Bifidobacterium: reduced in Wei [6], "largely unaffected" Actinobacteria in Parker [5], and a single prophylactic dose was associated with a 1.99-fold increase in Bifidobacterium infantis colonisation (95% CI 1.33 to 2.97) in 150 mother-infant dyads (Mumta trial, Pasha 2025) [12]. Parker also found fewer new enteroaggregative and enteropathogenic E. coli and Campylobacter colonisations after azithromycin [5], while Malawi found enteropathogenic E. coli abundance up [10].
• At-risk subgroups: Infants and young children (most data); the subset of adults with a lasting diversity drop [7]; people dosed repeatedly (resistance selection) [9][10]; people with prior C. difficile risk factors (label) [1].

Direction

Disturbance and resistance-selection risk (excess-risk framing). This is not the depletion of a nutrient. No supplement is implied.

Regulatory status

The label warns that Clostridioides difficile-associated diarrhea can range from mild to fatal colitis and may occur more than 2 months after antibiotic use; diarrhea occurs in 5 to 14% overall (4 to 5% in adult multiple-dose trials, 14% after a single 2 g dose) [1].

Population evidence: infants and children

Parker 2017 [5]: randomised placebo-controlled trial, infants 6 to 11 months, south India, 3-day course; 120 infants in the microbiota subset (60 per arm), 114 per protocol. Day 14 OTU count 68.1 ± 15.4 vs 73.6 ± 13.7 (p = 0.027, about 7% lower); Shannon 2.6 vs 2.8 (p = 0.087, not significant). Arm explained a small share of beta diversity (R2 0.020 unweighted UniFrac, 0.022 weighted, p under 0.05). Proteobacteria and Akkermansia muciniphila fell (A. muciniphila present in 20% of azithromycin recipients at baseline, absent after). Wei 2018 [6]: double-blind placebo-controlled trial, children 12 to 36 months with recurrent asthma-like episodes, 10 mg/kg/day for 3 days; stool at day 14 (N = 59) and age 4 (N = 49, 18 placebo). Observed richness fell 23% and Shannon 13%, driven by Actinobacteria with reduced Bifidobacterium; no difference in composition 13 to 39 months later (abstract only; no p-values stated in it).

Population evidence: adults

Anthony 2022 [7]: healthy adult volunteers followed before, during and 6 months after 4 antibiotic regimens including azithromycin. Richness and culturable bacteria dropped after treatment; most volunteers regained richness within about 2 months but taxonomy, resistome and metabolic output stayed altered; azithromycin slowed richness recovery and produced greater compositional distance from baseline (the comparator is not stated in the abstract); a subset had a lasting diversity drop. Read as a reconstructed abstract paraphrased by the fetch tool: arm sizes, doses and effect sizes were not retrieved (full text blocked).

Population evidence: mass treatment and resistome

MORDOR I, Niger [8][9]: 30 communities randomised to biannual azithromycin or placebo. At 24 months two Campylobacter species and 33 other gut bacteria were significantly reduced (differential species FDR under 0.01, log2 fold change over 2) and macrolide-resistance gene expression was increased (p = 0.004), while gamma diversity was not significantly altered (p = 0.08) [8]. Rectal-swab resistome: macrolide-resistance determinants 7.4 times higher at 36 months (95% CI 4.0 to 16.7) and 7.5 times higher at 48 months (95% CI 3.8 to 23.1) in the azithromycin villages, with 546 placebo and 504 azithromycin samples analysed at 48 months [9]. MORDOR Malawi [10]: 182 stool samples (60 baseline, 122 at 24 months), azithromycin 20 mg/kg in four biannual rounds. Proportion of macrolide-resistant bacteria rose (p under 0.001) and 30 species changed (15 down, 15 up, including Escherichia albertii and enteropathogenic E. coli up), but Shannon diversity was unchanged (p = 0.454) and treatment did not change overall composition (PERMANOVA p = 0.598).

Mechanism

Present. The drug binds bacterial 23S rRNA of the 50S subunit and blocks protein synthesis and subunit assembly [1]; commensal gut bacteria carrying susceptible ribosomes are exposed to it, and biliary excretion of unchanged drug delivers it to the gut [1]. Selection for macrolide-resistance determinants follows [9][10].

Independence check

Independent cohorts with azithromycin named and microbiome directly measured: Parker (India) [5], Wei (Denmark) [6], Anthony (adult volunteers) [7], Abeles (US, mixed) [11], Pasha (Pakistan, opposite direction on one taxon) [12]. Doan 2019 and Doan 2020 are the same Niger trial [8][9]. MORDOR Malawi [10] is a separate country and community set under the same umbrella registration (NCT02047981). The infant and child cohorts are not adults.

Why orange, not red

Several independent Tier A cohorts with a named mechanism support a real, measured disturbance, which clears orange. Red is withheld on three grounds: the diversity effect is small to moderate and time-bounded (about 7% to 23% at 12 to 14 days, recovered at 13 to 39 months in children [6], mostly within about 2 months in adults [7]); two cohorts found no diversity or composition change at 24 months [8][10]; and taxon-level direction conflicts across cohorts [5][6][12]. No cohort linked the microbiome change to a clinical or nutrient outcome. The resistance-selection signal is the most consistent finding [8][9][10] but it is a resistance outcome, not a nutrient state.

Counter-evidence held on record

Counter-evidence and confounding Confounding by indication is real: the infections and asthma-like episodes being treated, and age, geography and diet in the cohorts, all shape the microbiome; Parker and Wei used placebo controls, which addresses this, but the adult study [7] compares antibiotics with each other. Mass-treatment cohorts [8][9][10] are repeated biannual dosing, not a single course. Microbial change is not shown here to alter vitamin, short-chain fatty acid or other nutrient status: no azithromycin study retrieved measured those. Framing caution This is a disturbance and resistance-selection risk after a short course, not evidence of a depleted nutrient and not a reason to take a probiotic or supplement. Do not present it as permanent damage. Any diarrhea, especially over 2 months after a course, is a clinician question because of C. difficile [1].

Limits on what this shows

• At-risk subgroups: None established. Pregnant women and malaria-endemic populations in the trials have a high baseline anemia prevalence (44.1% and 41.3% in APPLe) [20].

Direction

Possible reduction in hemoglobin (context flag). Not an iron entry: iron was not measured in any source (see Iron). Anemia is an outcome, not iron deficiency (Hard Rule 2).

Regulatory status

Adult trials, over 1%: decreased hemoglobin, hematocrit, lymphocytes, neutrophils and blood glucose. Pediatric trials: "Anemia and leukopenia". Postmarketing: thrombocytopenia. The label does not mention hemolytic anemia [1].

Population evidence

APPLe trial [20]: 2,297 pregnant women (1,096 azithromycin 1 g, 1,087 placebo), anemia at 28 to 32 weeks 44.1% vs 41.3%, OR 1.07 (95% CI 0.88 to 1.30). Malawi antenatal trial [21]: 1,313 women in three arms (control 433, SP 439, azithromycin plus SP 441); mean hemoglobin and anemia prevalence did not differ between groups (no effect sizes in the abstract). MORDOR Niger malaria study [22]: annual vs biannual mass azithromycin, no significant hemoglobin difference between arms (no placebo comparator for this outcome).

Mechanism

Absent as a named mechanism. A PubMed search for azithromycin-induced hemolysis returned 7 records, none identifying azithromycin as the cause of hemolysis in a human; azithromycin appeared as a treatment or co-medication [31]. Methemoglobinemia and arterial oxygenation were not separately found.

Counter-evidence held on record

Counter-evidence and confounding The label laboratory list is not causally attributed and includes disease effects; the trials above are the stronger evidence and are null. Confounding by indication (infection, malaria, pregnancy) is presumed. Framing caution Do not state that azithromycin lowers oxygen delivery or causes anemia. This is a label flag, bounded by null randomised data.

Limits on what this shows

• Null findings: None specific. No human measurement (for example muscle or blood ATP, lactate or respirometry) after azithromycin was found. The one respirometry paper that surfaced for antibiotics excluded azithromycin [18].

Direction

Possible reduction of cellular ATP output (mechanistic plausibility). Not a nutrient deficiency and not independent of the Mitochondrial burden entry.

Regulatory status

Not addressed in the label [1].

Population evidence (Tier B, weak)

Fiorillo 2019 [16]: MCF7 ER-positive breast cancer cells; 1 micromolar doxycycline, 1 micromolar azithromycin and 250 micromolar vitamin C reported "strong inhibitory effects" on oxygen consumption and ATP production by metabolic flux analysis (reconstructed abstract; no numbers). The 1 micromolar azithromycin concentration is near the calculated plasma peak of about 0.67 micromolar, but doxycycline, a known mitochondrial-translation inhibitor, and vitamin C were co-applied.

Mechanism

Proposed: inhibition of the large mitochondrial ribosome and mitochondrial protein translation [16]. Azithromycin-alone oxygen consumption and ATP data were not found in Lamb 2015 [15] or elsewhere.

Counter-evidence held on record

Counter-evidence and confounding The effect is attributed to a three-component combination in cancer cells by the same group as the mitochondrial burden evidence; it shares its origin with that entry (see Overlap map). Framing caution Do not attribute low energy, fatigue or reduced ATP to azithromycin from this entry.