Metoprolol

Limits on what this shows

• Key negative or null findings: The Power et al. 2019 title finding, mitochondrial dysfunction "remains impaired" despite metoprolol, argues against metoprolol being the cause of the dysfunction in that model (the pre-existing right-ventricular hypertrophy is the more direct explanation) and against metoprolol correcting it. The H9c2 study found metoprolol still produced a measurable protective effect versus untreated stressed cells, only smaller than nebivolol's, which is a relative-effectiveness finding, not evidence metoprolol itself impairs mitochondria.
• At-risk subgroups: None established in humans. All positive animal signals come from disease models (diabetic heart, pulmonary-hypertensive right ventricle, ischemia-reperfusion) where confounding by indication is presumed and not excluded (Hard Rule 6): heart failure and diabetes are independently established causes of mitochondrial dysfunction, so a change observed in a treated diseased animal cannot be attributed to the drug without a diseased-untreated arm, which most of these studies did include as comparator but whose quantitative results were not accessible here.
• Dose/duration: Varies by study (not independently verified for most beyond the listing); the Power et al. rat model used short-duration treatment per its own title. No human exposure-duration data exists to report.

Regulatory status

Not addressed in either metoprolol label. No FDA labeling language on mitochondrial effects exists for metoprolol or any beta-blocker.

Population evidence

No Tier A human study was located. Tier B animal/cell-culture evidence with metoprolol specifically in the study, identified via PubMed search listings (full abstracts of most of these could not be opened during this review after repeated access blocks; titles and listing summaries are cited, flagged, and no statistic is drawn from any of them beyond what the listing itself displayed): a rat pulmonary-hypertension model (Power et al., PLoS One 2019) found right-ventricular mitochondrial dysfunction persisted after short-duration metoprolol treatment, i.e., metoprolol neither clearly worsened nor corrected it; an H9c2 cardiomyoblast study (Gul et al., BMC Pharmacol Toxicol 2025) found metoprolol produced smaller gains in mitochondrial biogenesis and antioxidant defense than nebivolol under angiotensin-II-induced stress, but did show some effect; a myocardial-stunning model (Le et al., 2024) found carvedilol more protective of mitochondrial parameters than metoprolol; a separate rat diabetic-heart study is reported (via search listing only, full text not opened) to show metoprolol repressing PGC1-alpha-mediated carnitine palmitoyltransferase-1B expression, a mitochondrial fatty-acid-oxidation gene.

Mechanism

No single named mechanism is established. Candidate pathways raised across these studies include reduced PGC1-alpha-driven mitochondrial biogenesis signaling in the diabetic heart, and unequal antioxidant/biogenesis support compared with nebivolol (which has independent nitric-oxide-mediated mitochondrial effects not shared by metoprolol). This is distinct from, but may share machinery with, the existing Coenzyme Q10 entry above (a direct electron-transport-chain component); no new human or drug-specific animal data linking metoprolol to CoQ10 synthesis or clearance was found beyond what that entry already documents, so this entry does not double-count the CoQ10 finding (see Overlap map).

Counter-evidence held on record

No Tier A human data. Multiple Tier B studies show metoprolol retaining at least partial protective or neutral effects rather than uniformly worsening mitochondrial parameters; the clearest "impairment" finding (Power et al.) is more consistent with disease-driven dysfunction that metoprolol did not reverse than with drug-induced harm. Most primary sources here could not be opened beyond their PubMed listing entry during this review; that access limitation is stated explicitly rather than treated as full verification. Framing caution for the consumer-facing surface Do not present this as "metoprolol damages mitochondria." The evidence is animal/cell-culture only, mixed in direction, and confounded by the cardiac disease states studied. A circulating consumer claim exists (see Claim audit table) naming metoprolol brands alongside atenolol as "toxic to mitochondria," sourced to a database entry for a different drug in the class; it is not supported at drug-specific human level and must not be repeated as established fact.

Limits on what this shows

• Key negative or null findings: Bank et al. 2007 found no significant difference between carvedilol and metoprolol on oxidative-stress markers in type 2 diabetes, a direct null result with metoprolol in the cohort. Step 4 counter-evidence rule applies directly to the rest: an active-comparator trial showing metoprolol did less well than nebivolol does not establish that metoprolol worsens oxidative stress relative to no treatment, only that it is a less effective antioxidant-supporting choice than one specific comparator in these particular trials.
• At-risk subgroups: None established at human Tier A strength. All human cohorts were hypertensive (Cicek et al. also coronary-intervention patients), so confounding by indication (hypertension and coronary disease both independently raise oxidative-stress markers) is presumed and not excluded by any of these active-comparator designs.
• Dose/duration: Not independently verified beyond listing-level detail for most studies; treatment durations in this class of trial are typically weeks to months. No dose figure is reported here.

Regulatory status

Not addressed in either metoprolol label.

Population evidence

Identified via a PubMed search listing (direction and species as characterized in that listing; full abstracts largely not independently opened after repeated access blocks, flagged below): Serg et al., Scand J Clin Lab Invest 2012, and Hayek et al., J Am Soc Hypertens 2015, both human, both nebivolol-versus-metoprolol in essential hypertension, both reporting nebivolol more favorable on oxidative-stress and related vascular markers than metoprolol; Celik et al., J Hypertens 2006, human, nebivolol versus metoprolol on oxidative stress, insulin resistance, and adiponectin, again favoring nebivolol; Bank et al., Am J Hypertens 2007, human, carvedilol versus metoprolol in type 2 diabetes, found no significant between-group difference in oxidative-stress markers; Cicek et al., Anadolu Kardiyol Derg 2006, human, metoprolol and coronary-angioplasty-induced oxidative stress and homocysteine; Ma et al., J Hypertens 2012, human, a felodipine-irbesartan combination produced less oxidative stress than a metoprolol-containing regimen. All of these have metoprolol directly in the studied cohort (Tier A by the cohort test), but every one is an active-comparator design.

Mechanism

No mechanism specific to metoprolol's beta-1 blockade is established as pro-oxidant. Nebivolol's comparative advantage in several of these trials is attributed in the literature to its own additional nitric-oxide-mediated antioxidant action, not to metoprolol actively generating oxidative stress; the two animal/lower-organism studies located (Oyedele et al. 2023, cockroach nymphs; Martinez-Rodriguez et al. 2018, common carp) did find metoprolol itself reduced antioxidant enzyme activity and induced oxidative damage directly, which is the closest thing to a drug-specific pro-oxidant mechanism in this evidence base, but neither is a mammalian or human model.

Counter-evidence held on record

At least one direct null result (Bank et al. 2007). No placebo-controlled human trial isolating metoprolol's own effect on oxidative stress from hypertension itself was located. Full abstracts for the nebivolol-comparator trials could not be opened during this review after repeated 429 responses from the hosting journals and from PubMed and Semantic Scholar; this is stated explicitly rather than treated as verified, and no p-value or percentage figure from those trials is cited anywhere in this entry. Framing caution for the consumer-facing surface Do not present this as "metoprolol causes oxidative stress" or as grounds for an antioxidant-supplement recommendation. The strongest same-species evidence for a direct pro-oxidant effect comes from insect and fish toxicology studies, not human data, and the human data is comparator-bound and mixed with a null result.

Limits on what this shows

• Key negative or null findings: The Suliburska et al. 2014 result itself is the key null finding: with metoprolol directly in a four-drug comparative cohort, only indapamide and amlodipine (a diuretic and a calcium-channel blocker, neither a beta-blocker) produced significant mineral disturbance.
• At-risk subgroups: None identified.
• Dose/duration: Suliburska et al.: 45-day treatment in rats. No human exposure data exists to report.

Regulatory status

Not addressed in either metoprolol label.

Population evidence

Suliburska, Bogdanski & Jakubowski, Eur J Pharmacol 2014;738:326-31 (PMID 24927993): spontaneously hypertensive rats received perindopril, metoprolol, indapamide, amlodipine, or no treatment for 45 days; serum, erythrocyte, and tissue zinc, copper, and iron were measured by flame atomic absorption spectrometry. The verified abstract text states that indapamide and amlodipine significantly lowered zinc levels and reduced kidney copper; metoprolol is not named among the drugs producing a significant mineral change. This is a genuine Tier B (animal) drug-specific null finding, not an absence of a study. No other PubMed-indexed study naming metoprolol and copper, ceruloplasmin, or copper metabolism was located; the only other hits were a carvedilol superoxide-dismutase study (a different beta-blocker, unrelated mechanism) and a 1992 in-vitro LDL-oxidation assay using copper ions as a laboratory oxidation catalyst, not as a measure of the drug's effect on the body's copper status.

Mechanism

None identified. Metoprolol has no documented chelating, gastric-pH-altering, or renal copper-wasting mechanism in its regulatory labeling (see Pharmacokinetic basis above), and no in-vitro or animal study proposing such a mechanism was located.

Counter-evidence held on record

A direct, drug-specific Tier B study looked for this effect and did not find it. This is documented as the evidence, not discarded, and is the reason no yellow grade is assigned; per the governing rule, this absence of a positive finding is not converted into a safety reassurance either. Framing caution for the consumer-facing surface Do not present this as "metoprolol is safe for copper status," which would overstate a single animal null result, and do not present it as a deficiency claim, which the evidence does not support. It should read as an evidence gap.

Limits on what this shows

• Key negative or null findings: The Suliburska et al. 2014 iron measurement is itself the key null finding, with metoprolol directly in the comparative cohort.
• At-risk subgroups: None identified.
• Dose/duration: Suliburska et al.: 45-day treatment in rats. No human exposure data exists to report.

Regulatory status

Not addressed in either metoprolol label.

Population evidence

Suliburska, Bogdanski & Jakubowski, Eur J Pharmacol 2014;738:326-31 (PMID 24927993), the same spontaneously-hypertensive-rat, 45-day, four-drug comparative study described in the Copper entry above, measured serum, erythrocyte, and tissue iron alongside zinc and copper. The verified abstract text names only zinc (and, secondarily, kidney copper) as significantly disturbed, by indapamide and amlodipine; no significant iron effect is reported for any of the four drugs, including metoprolol, in the accessible abstract text. No other PubMed-indexed study naming metoprolol and iron status, ferritin, hemoglobin, or iron deficiency was located despite multiple search phrasings.

Mechanism

None identified. Metoprolol has no documented gastrointestinal, absorptive, or renal iron-handling mechanism in its regulatory labeling, and beta-blockers as a class are not established GI-bleeding or iron-chelating agents (unlike, for example, NSAIDs or certain anticoagulants).

Counter-evidence held on record

A direct, drug-specific Tier B study measured this parameter with metoprolol in the cohort and reported no significant effect. This is the evidence on record, not an absence of a search. Framing caution for the consumer-facing surface Do not present this as "metoprolol is safe for iron status," and do not present it as a deficiency claim. It should read as an evidence gap, exactly as printed here.

Limits on what this shows

• Key negative or null findings: No placebo or drug-naive comparator arm; the comparison is within the same uncontrolled-hypertension cohort, medicated timepoints against non-medicated timepoints, so a treatment-adherence or dietary-behavior confound cannot be fully excluded. No study measuring gut microbiome composition (rather than urinary metabolites) in metoprolol users was located. Two additional studies located in this search (Guo et al. 2022, J Adv Res; Zhang et al. 2024, Drug Metab Dispos ) run the opposite direction, gut microbiota and probiotic supplementation altering metoprolol's own pharmacokinetics via CYP450 activity, and are excluded from this grade as a nutrient/microbiome-affects-drug finding, not a drug-affects-microbiome one (see Overlap map).
• At-risk subgroups: None established; the source cohort was adults with uncontrolled hypertension, so confounding by the underlying cardiovascular and metabolic disease state, rather than metoprolol specifically, has not been excluded.
• Dose/duration: Metoprolol succinate at each patient's routine clinical dose (not separately reported by dose band in the accessible summary); urinary sampling weekly across a 6-week treatment window.

Regulatory status

Not addressed in either metoprolol label. No FDA labeling language exists on gut microbiota effects for metoprolol or any beta-blocker.

Population evidence

Brocker et al., Human Genomics 2020: a prospective pragmatic study of 86 adults (30-80 years) with uncontrolled hypertension, 77 completing follow-up, on metoprolol succinate, with 283 urine samples collected weekly over 6 weeks and analyzed by untargeted metabolomics. Supervised multivariate (OPLS-DA) modeling identified three gut-microbiota-derived urinary metabolites, hippuric acid, hydroxyhippuric acid, and methyluric acid, among the strongest features separating metoprolol-treated from non-medicated timepoints, all significantly elevated on treatment. This is Tier A: human, metoprolol succinate specifically named and dosed as part of routine care, a microbiome-derived parameter directly measured (not inferred from a clinical outcome).

Mechanism

Hippuric acid and its hydroxylated form are host-microbial co-metabolites, produced when gut bacteria break down dietary aromatic compounds (chiefly polyphenols) into benzoate derivatives that the liver and kidney conjugate with glycine. A rise in urinary output of these metabolites indicates a shift in gut microbial metabolic activity or composition attributable to metoprolol exposure; the paper does not identify which bacterial taxa shifted, so this is a functional signature of microbiome change, not a compositional (16S/shotgun sequencing) one.

Counter-evidence held on record

Single study; no independent replication located. No direct microbiome composition data. Confounding by indication (uncontrolled hypertension itself, and the diet/lifestyle factors that accompany it) is not excluded by the study design, since there is no drug-naive comparator arm within the same population. Framing caution for the consumer-facing surface This must never be worded as "metoprolol damages gut bacteria" or paired with a probiotic recommendation. The metabolite shift's clinical significance, if any, is not established; it should read as a documented pharmacometabolomic finding worth further study, not a health risk claim.

Limits on what this shows

• Key negative or null findings: No evidence located that metoprolol impairs oxygen utilization at the mitochondrial or cellular level (a distinct question from delivery via blood flow); the mechanism here is macrovascular/hemodynamic, not a tissue-level utilization defect. A Cochrane review series (Paravastu et al., several years) on beta-blockers in peripheral arterial disease did not find beta-blockers worsen claudication outcomes in the general PAD population, arguing against a clinically meaningful oxygen-delivery deficit for most patients despite the measurable resting-flow reduction.
• At-risk subgroups: Patients with pre-existing peripheral arterial disease or Raynaud phenomenon are the plausible subgroup for clinically noticeable cold extremities, consistent with general beta-blocker prescribing caution, though the Cochrane review above did not find a population-level harm signal in PAD.
• Dose/duration: Not independently verified beyond listing-level detail for either study; both describe resting-state measurement rather than a defined exposure window.

Regulatory status

Cold extremities and reduced peripheral circulation are recognized class-level beta-blocker effects in general prescribing literature; not framed in either metoprolol label as a nutrient or oxygen-delivery deficiency.

Population evidence

Karnik, Valentin & Slany, Angiology 1987, human, compared beta-1 blockers with and without intrinsic sympathomimetic activity; the PubMed search-listing entry for this study states directly that "metoprolol significantly lowered calf blood flow at rest." Svensson et al., Clin Sci (Lond) 1981, human, is titled "Metoprolol and pindolol in hypertension: different effects on peripheral haemodynamics," indicating a metoprolol-specific peripheral-hemodynamic comparison. Both are Tier A by the cohort test (metoprolol named and directly measured), but only the listing-level text could be accessed for either during this review; the full abstract pages returned repeated access blocks, so no additional magnitude, sample size, or p-value is cited from either beyond the quoted listing phrase above, which is flagged as such.

Mechanism

Beta-1 blockade reduces heart rate and myocardial contractility, lowering cardiac output; with beta-2-mediated vasodilation relatively unopposed by beta-1 blockade but systemic hemodynamics still net reduced, resting limb blood flow falls in several beta-blocker studies. This is squarely the drug's intended and labeled class of pharmacologic action (reducing cardiac workload and oxygen demand, which is therapeutic in angina and hypertension), not a novel nutrient-transport or mitochondrial-oxygen-utilization defect, so it is graded here as a context flag consistent with Hard Rule 3, the same treatment given to the potassium and melatonin entries above.

Counter-evidence held on record

This is the drug's own hemodynamic mechanism of action, not a nutrient-transport defect; Hard Rule 3 requires it be flagged as such rather than filed as a new deficiency category. Full-text access to both primary studies was blocked during this review; only the listing-level description is cited, and no statistic beyond the directly quoted phrase is used. Framing caution for the consumer-facing surface Never present this as "metoprolol starves your tissues of oxygen" or pair it with an iron, B12, or antioxidant recommendation. If surfaced, it belongs with the existing cold-extremities/circulation prescribing caution, not with a nutrient-deficiency claim.

Limits on what this shows

• Key negative or null findings: The Sharma et al. 2008 title itself reports metoprolol improving cardiac function and modulating (not simply depleting) metabolism in the diabetic rat heart, which argues against a straightforward depletion narrative. Reducing myocardial oxygen and substrate demand is metoprolol's intended therapeutic mechanism in ischemic and failing hearts (Hard Rule 3 applies: this is the drug's own mechanism, not a novel deficiency), which further complicates attributing any energy-metabolism shift in disease-model studies to harm rather than intended pharmacology.
• At-risk subgroups: None established in humans. All positive animal signals are disease-model specific (diabetic heart, post-ischemic muscle), so confounding by the cardiac or metabolic disease itself is presumed and not excluded (Hard Rule 6).
• Dose/duration: Not independently verified beyond listing-level detail for any of these studies.

Regulatory status

Not addressed in either metoprolol label.

Population evidence

No Tier A human study was located despite searching multiple phrasings (metoprolol plus ATP production, skeletal muscle bioenergetics, exercise energy metabolism). Tier B animal evidence, identified via PubMed search listing with full text not independently opened during this review (flagged, no statistic cited beyond title/topic): Fellenius, Hedberg & Karlsson, Acta Physiol Scand 1980, rat, titled around beta-receptor blockade and adrenaline-induced changes in redox and energy state in m. vastus lateralis and m. soleus, with metoprolol and propranolol both named in the listing as tested; Sharma et al., Am J Physiol Heart Circ Physiol 2008, rat, titled "Metoprolol improves cardiac function and modulates cardiac metabolism in the streptozotocin-diabetic rat," which on its face describes a beneficial, not depleting, effect on diabetic cardiac metabolism; a separate diabetic-rat study (title only, full text not opened) reports metoprolol repressing PGC1-alpha-mediated carnitine palmitoyltransferase-1B expression, a fatty-acid-oxidation/ATP-generation pathway gene, in the diabetic heart specifically.

Mechanism

No single mechanism is established for metoprolol reducing ATP production. The PGC1-alpha/CPT-1B repression finding is mechanistically plausible as a route to altered fatty-acid-driven ATP generation, but it comes from a diabetic-heart model where excessive fatty-acid oxidation is itself part of the disease's inefficiency, so repressing it could represent a therapeutic normalization rather than a harmful depletion; this ambiguity is not resolved by the available listing-level information. This entry cross-references, rather than duplicates, the existing Coenzyme Q10 entry above (CoQ10 is a direct electron-transport-chain component feeding ATP synthase); no new metoprolol-specific human or animal CoQ10 data beyond that entry was found in this search (see Overlap map).

Counter-evidence held on record

No Tier A human data. The clearest titled effect in this evidence base (Sharma et al. 2008) describes improvement, not depletion, in diabetic cardiac metabolism. Full-text access to all four animal studies cited here was blocked during this review; only listing-level titles and topics are used, and no numeric result is cited from any of them. Framing caution for the consumer-facing surface Do not present this as "metoprolol drains your cellular energy." The strongest specific evidence located describes metoprolol modulating, and in one disease-model title improving, cardiac energy metabolism, not depleting it; framing this as a fatigue-causing ATP deficiency is not supported.