Allopurinol

Limits on what this shows

• Null findings: PubMed "allopurinol mitochondrial function" (page 1 read): no record reported mitochondrial toxicity from allopurinol.

Regulatory status

No mitochondrial statement in the labels read [1][2][3][4].

Population evidence

None in humans. Cristóbal-García 2015 [26], Oxid Med Cell Longev: rats given oxonic acid, oxonic acid plus allopurinol (150 mg/L), oxonic acid plus Tempol, or vehicle; renal oxidative markers, tissue ATP, and oxygen consumption and aconitase activity in isolated renal mitochondria were assessed; allopurinol prevented the hypertension, vasoconstriction, tubular damage and oxidative changes (the reconstructed abstract does not give the mitochondrial values). A 1992 canine warm-ischemia liver study on mitochondrial function with allopurinol appeared in the PubMed listing and was not opened.

Mechanism

Proposed: less xanthine oxidase-derived oxidant load protects mitochondrial function. Not shown in healthy tissue.

Direction

Reverse or protective in a disease model. Not depletion.

Counter-evidence held on record

Counter-evidence The protective effect is relative to hyperuricemia-induced injury, so it does not show an effect of allopurinol alone. Animal only. Framing caution Not a mitochondrial-damage claim and not a mitochondrial-support claim. Do not suggest CoQ10 or other mitochondrial supplements from this entry.

Limits on what this shows

• Null findings: Sun 2022 [20]: randomized double-blind placebo-controlled trial, 28 participants (14 per group) with stage 3 CKD and hyperuricemia, allopurinol 300 mg daily for 12 weeks (full text read through a summarizing fetch tool). Urate fell 3.60 versus 0.26 mg/dL; serum XO activity did not change (-0.14 versus -0.04 mU/mL, P=0.70); endothelial XO expression unchanged; oxidized LDL and endothelial nitrotyrosine were measured and the authors conclude allopurinol "does not appear to result in significant antioxidant effects in this patient population". A 2004 randomized trial titled "Ineffectiveness of allopurinol in reduction of oxidative stress in diabetic patients" [21] was seen by title and metadata only (abstract not available) and is not relied on.
• At-risk subgroups: Not defined. Heart failure, diabetes and CKD are disease contexts in which the findings diverge.

Regulatory status

No oxidative-stress statement in the label sections read [1][2][3][4].

Population evidence

Farquharson 2002 [18]: randomized, placebo-controlled, double-blind crossover, 11 patients with chronic heart failure, allopurinol 300 mg daily (reconstructed abstract). Forearm blood flow response to acetylcholine 181 plus or minus 19% versus 120 plus or minus 22% (P=0.003); malondialdehyde 346 plus or minus 128 versus 461 plus or minus 101 nmol/L (P=0.03). Dogan 2010 [22]: randomized single-blind trial, 100 diabetic patients, 900 mg daily for 12 weeks; flow-mediated dilation improved (a functional outcome; oxidative markers not reported in the abstract).

Mechanism

Present. The heart-failure authors attribute excess oxidant production to xanthine oxidase activity [18][23], and inhibition lowers that source. Allopurinol itself did not inhibit linolenic acid peroxidation at 10 to 1000 µM in vitro and showed no antioxidant activity in rats at doses up to 100 mg/kg, while XO inhibition in liver and intestine was dose dependent [19].

Counter-evidence held on record

Counter-evidence and confounding Findings are discordant across diseases and rest on very small trials. The positive trial measured one marker. Disease-model rat studies seen in listings were not used for this human-facing claim. Framing caution This is a reverse-direction finding. It is not a deficiency claim and not an antioxidant-benefit claim. Do not describe allopurinol as depleting antioxidants, and do not suggest antioxidant supplements from this entry.

Limits on what this shows

• Null findings: Boyett [8] (above). PubMed "hemochromatosis allopurinol xanthine oxidase ferritin" returned zero records; a second hemochromatosis query was rate limited and not retrieved. No study in hemochromatosis or iron-overload patients was found.
• At-risk subgroups: People with hemochromatosis or other iron overload: no evidence located in either direction. This is an evidence gap for that subgroup, not reassurance.

Regulatory status

Not mentioned. A keyword check of four DailyMed labels (Mylan revised November 2025 [1]; Actavis [2]; Accord revised December 2023 [3]; Zyloprim 2009 archive [4]) for iron, ferrous, hemochromatosis, ferritin and hepatic iron returned no matches. These labels were read through a summarizing fetch tool, not as raw text.

Population evidence

Boyett 1968 [8], Blood: oral and intravenous ferrokinetic studies in 9 patients with gout or hyperuricemia, each studied in a control period and again on allopurinol; "allopurinol produced no measurable effect on iron metabolism" (absorption, storage, red-cell incorporation; reconstructed abstract). Emmerson 1966 (human) [9], Powell 1966 (rat) [10] and Grace 1970 [11] were located by title and metadata only and could not be read, so their findings are not used. A 1978 study of 8 porphyria patients and a 1975 JAMA letter appeared in the PubMed listing and were not opened.

Animal evidence

Houze 1991 [12], rats: acute ethanol raised total non-heme iron and low-molecular-weight iron in liver and cerebellum; allopurinol given before ethanol "prevents these changes of elements". This is protection in an ethanol model, not an allopurinol effect at baseline.

Mechanism

Not established in the sources opened. The title record of [11] ("Effect of allopurinol on iron mobilization") shows the question was asked; no readable abstract shows an answer. Direct, opened evidence for hepatic iron uptake or release by allopurinol does not exist in this dossier.

Counter-evidence held on record

Counter-evidence and confounding The human study had 9 patients and is from 1968. Gout and hyperuricemia patients are a different population from iron-loaded patients. Rat data cannot be mapped to dose or duration in humans. Framing caution No iron supplementation or iron avoidance advice comes from this entry. Absence of a label statement is not evidence of safety for people with iron overload; those patients follow their treating clinician. Iron deficiency is not anemia, and drug-induced marrow aplasia (see Oxygen delivery/utilization) is not iron deficiency.

Limits on what this shows

• Null findings: None located; no copper measurement in allopurinol users (PubMed "allopurinol copper complex", 6 records, none in human users).

Regulatory status

Not mentioned in the labels read [1][2][3][4].

Population evidence

None in humans. Malkiel 1993 [13] (reconstructed abstract): spectrophotometry showed a 1:1 allopurinol-Cu(II) complex (absorption peak 364 nm), slower copper-catalysed ascorbate oxidation and less copper-mediated, ascorbate-driven DNA breakage. Lapenna 1997 [14]: allopurinol at 9 to 58 µM counteracted copper-catalysed oxidation of human non-HDL lipoproteins (thiobarbituric acid reactants, conjugated dienes); oxypurinol was ineffectual; fluorescence quenching indicated only allopurinol interacted with copper. Ko 1990 [15] (allopurinol-ascorbate-copper complex) was seen by metadata only and not read. Houze 1991 [12], rats: ethanol lowered selenium, zinc and copper in tissue; allopurinol before ethanol prevented the changes.

Mechanism

Chelation chemistry is shown in vitro. Whether it occurs in plasma or tissue, and whether it changes copper absorption, distribution or excretion, is not shown.

Direction

Complexation in vitro and protection against an ethanol-induced fall in rats. Not depletion.

Counter-evidence held on record

Counter-evidence The label gives allopurinol a plasma half-life of about 1 to 2 hours [1], and the long-lived metabolite oxypurinol did not bind copper in the lipoprotein study [14], so the relevant exposure is brief. Binding in a flask does not show a status change. Framing caution Mechanistic curiosity only. Not a deficiency claim, not a reverse claim of copper retention, and not a reason to supplement or restrict copper.

Limits on what this shows

• Null findings: PubMed "allopurinol 16S rRNA fecal gout patients" returned zero records; "allopurinol gut microbiota" (4 pages, page 1 read) showed no human trial comparing allopurinol users with untreated gout patients.

Regulatory status

No microbiome statement in the labels read. The label notes about 20% of an oral dose is found in feces [1][4], which means some luminal exposure; the label draws no microbiome conclusion.

Population evidence

Lin 2023 [28], BMC Complement Med Ther, gout mice (reconstructed abstract): allopurinol reduced serum urate, liver xanthine oxidase and inflammatory markers; Simiao decoction "had a greater impact on gut microbiota than allopurinol" in restoring Proteobacteria and Helicobacter abundance; fecal transplant from treated mice was used to test mediation. Kondratiuk 2020 [27], J Med Life: 130 men with gout, allopurinol 300 mg daily in both groups, synbiotics added in 68; fecal microbiota stabilization was reported in the synbiotic arm; the design has no allopurinol-free comparison.

Mechanism

Plausible but unproven: urate-lowering and purine availability may change gut bacteria that degrade purines and urate. A 2024 Heliyon mouse paper on hyperuricemia and gut barrier was opened as an abstract and states nothing about allopurinol, so it supplies no allopurinol finding.

Direction

Unclear. Could be a normalization of disease-associated change; could be a drug effect. Not distinguishable.

Counter-evidence held on record

Counter-evidence and confounding Gout and hyperuricemia themselves shift microbiota in the models seen. Animal data in a decoction paper cannot size a human effect. Framing caution Not a dysbiosis claim. Do not suggest probiotics or synbiotics from this entry.

Limits on what this shows

• Null findings: No study measuring hemoglobin, hematocrit or red-cell mass in a general allopurinol cohort versus non-users was retrieved (PubMed "allopurinol anemia", 129 results, page 1 read: case reports and reviews, no cohort measuring hemoglobin).
• At-risk subgroups: Renal impairment appears in both opened case reports [30][31]; co-prescription of azathioprine or mercaptopurine is a label-listed interaction that raises myelosuppression risk [2]. Neither is a nutrient finding.

Regulatory status

Present, as toxicity. Mylan label section 5.5: "Myelosuppression, manifested by anemia, leukopenia or thrombocytopenia, has been reported in patients receiving allopurinol tablets. The cytopenias have occurred as early as 6 weeks up to 6 years after the initiation of therapy." Adverse reactions listed include anemia, hemolytic anemia, aplastic anemia and pancytopenia [1] (read through a summarizing fetch tool).

Population evidence

Case reports only, Tier B and drug-specific. Kim 2009 [30]: 37-year-old woman with stage III CKD, pancytopenia after 5 months of allopurinol, marrow cellularity under 20%, recovery to about 70% cellularity over 6 months after stopping the drug with transfusion and prednisolone. Gosavi 2020 [31]: middle-aged woman on allopurinol for 7 months, normocytic anemia (Hb 3.2 g/dL) and platelets 1000/mm3 as reported, death from leukopenic sepsis; the authors state nutritional, hemolytic and infective causes were ruled out. Further case-report titles (1986 and 1990 aplastic anemia, 2021 azathioprine plus allopurinol severe anemia) appeared in the PubMed listing and were not opened. No incidence figure was retrieved.

Reverse-direction finding

Cappola 2001 [23]: 9 patients with idiopathic dilated cardiomyopathy (ejection fraction 29 plus or minus 3%), intracoronary allopurinol. Myocardial oxygen consumption fell (peak effect -16 plus or minus 5%, P under 0.01) without parallel falls in contractility or stroke work; stroke work per unit oxygen consumption rose 40 plus or minus 17%. Acute physiologic study from a reconstructed abstract; not a measure of hemoglobin, red-cell mass or arterial oxygen delivery.

Mechanism

Marrow toxicity: not defined in the sources opened (idiosyncratic or hypersensitivity-type; the label does not name a mechanism in the sections read). Oxygen utilization: authors propose xanthine oxidase inhibition reduces oxidative inefficiency of the failing myocardium [23].

Counter-evidence held on record

Counter-evidence and confounding Case reports cannot give a rate and cannot exclude other causes of aplasia. Gosavi [31] was a fatal single case with many co-factors. The oxygen-consumption study is acute, intracoronary and 9 patients. Framing caution Anemia is not iron deficiency and marrow aplasia is not a nutrient deficiency (Hard Rule 2). Do not link this entry to iron, B12 or folate supplementation. It is a drug-toxicity pointer that belongs with prescriber monitoring.

Limits on what this shows

• Null findings: Bertorini [25]. That trial combined allopurinol with adenine and enrolled a disease population, so it does not isolate allopurinol in healthy tissue.

Regulatory status

No energy-metabolism statement in the labels read [1][2][3][4].

Population evidence

Lasley 1988 [24], J Clin Invest, isolated rat heart after global ischemia (reconstructed abstract): treated hearts had greater ATP and better functional recovery, attributed to enhanced salvage of hypoxanthine into adenine nucleotides. Cristóbal-García 2015 [26], rats: oxonic acid hyperuricemia with or without allopurinol 150 mg/L; kidney ATP, mitochondrial oxygen consumption and aconitase were assessed and "treatments with allopurinol prevented these alterations" (abstract does not give ATP values). Bertorini 1985 [25], Neurology: 18-month double-blind trial, 14 boys with Duchenne muscular dystrophy given allopurinol plus adenine; muscle ATP was lower in Duchenne (P under 0.02) and "did not change with therapy"; no correction of adenine nucleotide degradation and no significant clinical difference from placebo.

Mechanism

Present: blocking hypoxanthine to xanthine to urate conversion leaves hypoxanthine available for the purine salvage pathway, which rebuilds adenine nucleotides [24].

Direction

Reverse or neutral. Not depletion.

Counter-evidence held on record

Counter-evidence Ex vivo rat hearts and a rodent disease model are Tier B and cannot be carried to ordinary gout patients. The efficiency finding in humans [23] measured oxygen use, not ATP, and is filed under Oxygen delivery/utilization. Framing caution Not a "low energy" explanation and not a supplement prompt. Kept as its own entry, independent of Mitochondrial burden and Oxygen delivery/utilization; shared sources are disclosed in the overlap map.