Bupropion

Limits on what this shows

• Key negative/null finding: Complex II+III activity and complex-II-linked ATP kinetics were stimulated, not inhibited, in the same mitochondrial study; effects were measured at supratherapeutic in vitro concentrations (50-100 µmol/L), well above typical clinical plasma bupropion levels (roughly 0.1-2 µmol/L at therapeutic dosing), which bounds clinical relevance.
• At-risk subgroups: None established clinically; the hepatocyte-toxicity literature is most relevant to bupropion's known (rare) idiosyncratic hepatotoxicity rather than to a general population mitochondrial-burden claim.

Regulatory status

Not addressed in the FDA label.

Population evidence

None clinical. Two Tier B bupropion-specific in vitro studies: (1) isolated pig brain mitochondria: complex I activity 82.1±6.8% of control at 100 µmol/L bupropion (p=0.045); complex IV 78.6±3.8% of control at 100 µmol/L (p=0.001); complex II+III activity mildly stimulated, 104.5±1.2% at 100 µmol/L; bupropion was the only tested antidepressant that partially inhibited complex II-linked respiration (Antioxidants, 2023). (2) primary rat hepatocytes and, in a separate synthetic-cathinone toxicology screen, HepG2 cells: bupropion caused mitochondrial depolarization ("mitochondrial collapse") alongside a surge in ROS, glutathione depletion, and lipid peroxidation, partly reversible with N-acetylcysteine, alpha-tocopherol succinate, or cyclosporine A (Pharmacopsychiatry-affiliated toxicology study, 2017).

Mechanism

Direct interference with electron transport chain complexes I and IV and with mitochondrial membrane potential, demonstrated in isolated mitochondria and intact hepatocytes; complex II-linked respiration was spared or mildly stimulated, so the effect is complex-specific, not global mitochondrial poisoning.

Counter-evidence held on record

All positive findings are in vitro/isolated-mitochondria or hepatocyte-culture, at concentrations above typical therapeutic plasma exposure; no in vivo or clinical mitochondrial marker (e.g., blood lactate/pyruvate ratio, muscle biopsy) has been reported for bupropion. This evidence base is more directly relevant to bupropion's known idiosyncratic hepatotoxicity risk than to a general "mitochondrial burden" claim for typical users; it should not be read as evidence that ordinary therapeutic dosing measurably burdens mitochondria in patients.

Limits on what this shows

• Key negative/null finding: The 28-day oral rat study is the closest analog to ordinary human dosing in this evidence base and found no significant oxidative-stress signal versus control; this is recorded as the most clinically relevant single data point available.

Regulatory status

Not addressed in the FDA label.

Population evidence

Three Tier B bupropion-specific studies with three different directions: (1) primary rat hepatocytes, toxic in vitro concentrations: "a surge in ROS formation, depletion of intracellular glutathione, elevation of LPO, and mitochondrial collapse" (2017). (2) Male Wistar rats, bilateral carotid occlusion stroke model, bupropion 60-100 mg/kg IP pretreatment: reduced MDA (lipid peroxidation) at 100 mg/kg, increased SOD activity at both doses, no significant change in catalase or GSH, reduced IL-1β/TNF-α/NO2- and increased IL-10 (2025). (3) Female Wistar rats, 20 mg/kg oral bupropion for 28 days: total oxidant status, total antioxidant status, and oxidative stress index not significantly different from control (p=0.198, 0.108; only the escitalopram arm differed significantly from control, p=0.042) (East J Med).

Mechanism

Concentration- and context-dependent: supratherapeutic in vitro hepatocyte exposure is pro-oxidant via mitochondrial injury (see Mitochondrial burden, same source); acute high-dose ischemic-stress pretreatment is net antioxidant/anti-inflammatory; chronic oral dosing at a lower, more clinically comparable dose shows no net systemic redox shift.

Counter-evidence held on record

Reconciling these three findings: dose and context, not a fixed pro- or antioxidant identity, appear to drive the direction. None is a Tier A human study, so none can anchor a color above yellow, and no single "bupropion causes oxidative stress" or "bupropion is an antioxidant" claim is supported as a general statement.

Limits on what this shows

• Key negative/null finding: A direct PubMed search for "bupropion copper" returned no drug-nutrient study; the only relevant hit was the zinc/copper-ratio paper above.

Regulatory status

Not mentioned in the FDA label.

Population evidence

Tier B animal study (see Zinc entry, same source): serum copper was measured as the denominator of the zinc/copper ratio in mice under pathological/zinc-deficient conditions, across imipramine, escitalopram, reboxetine, and bupropion (15 mg/kg) arms. The paper's own findings are reported as a ratio; no bupropion-specific absolute serum-copper effect independent of the ratio was described.

Mechanism

None established. No absorption-interference, ceruloplasmin, or hepatic-copper-handling mechanism connects bupropion to copper status in any source located.

Counter-evidence held on record

This entry rests entirely on a ratio study, not an independent copper measurement; see the Overlap map. It is graded yellow rather than ungraded only because that Tier B animal source exists and does touch copper directly, but the evidentiary base is thin and should not be read as stronger than the zinc entry it shares its data with.

Limits on what this shows

• Why no grade: Both conditions of the Step 7 dual test are met: (1) no Tier B or Tier C evidence exists connecting bupropion to iron absorption, storage, or handling, so there is nothing to support even a yellow grade; (2) no consumer nutrient-depletion source located during this review claims bupropion depletes or affects iron (the consumer sources found claim CoQ10 and B-vitamins, not iron), so there is no claim to rebut as white.

Research channels tried

PubMed search-listing queries for "bupropion iron metabolism" (2 irrelevant results: an obesity/fertility review and an unrelated female-sexual-desire trial), "bupropion ferritin" (3 results, all about restless-legs-syndrome ferritin thresholds as a differential diagnosis, none about bupropion affecting ferritin), and "bupropion iron overload" via general web search (only drug-interaction-checker pages showing "no known interaction" and an unrelated restless-legs-syndrome iron-vs-bupropion comparative-treatment letter that explicitly does not discuss a bupropion-iron interaction). DailyMed/FDA label: no mention of iron, ferritin, transferrin, or hematinic effects tied to bupropion specifically (distinct from the general postmarketing anemia listing captured under Oxygen delivery/utilization, which is a clinical-outcome entry, not an iron-status entry per Hard Rule 2). Europe PMC and Semantic Scholar REST APIs were attempted for a broader sweep and returned HTTP 429 on every attempt this session; this is disclosed as a tooling limitation, not treated as evidence of absence, but the PubMed and general-web channels that did work returned consistently negative results across multiple phrasings, which is the basis for concluding this is a genuine literature gap rather than a single blocked attempt.

Limits on what this shows

• Key negative/null finding: No direct antimicrobial activity in vitro (study 2) is itself the key null/counter-finding, and it constrains how the favorable animal finding (study 1) should be interpreted: as host-mediated, not bacteriocidal/bacteriostatic.
• At-risk subgroups: None identified; both studies are animal/in vitro only, so no human subgroup claim is supported.

Regulatory status

Not addressed in the FDA label.

Population evidence

Two Tier B bupropion-specific studies: (1) male Sprague-Dawley rats (n=35) in a chronic-restraint-stress depression model: oral bupropion "modulated the gut microbiota composition in favor of beneficial bacteria such as Romboutsia and Muribaculum" while suppressing Staphylococcus, Streptococcus, and Bacteroides, and "improved the abnormal levels of acetic acid, butyric acid, tryptophan and its derivatives, nicotinamide, and biotin"; injectable bupropion did not fully replicate the oral effect (2025). (2) a 12-strain gut-commensal-bacteria screen: bupropion showed MIC >800 µg/mL or no inhibitory activity against any of the 12 strains tested, with no significant reduction in bacterial viability at any concentration tested, in contrast to desipramine and aripiprazole, which showed potent direct antibacterial effects (Nature Scientific Reports, 2020).

Mechanism

Because bupropion shows no direct antibacterial activity (study 2), the favorable compositional shift seen in study 1 is more plausibly a host-mediated effect (stress-axis, metabolic, or immune modulation, consistent with the same paper's findings on CD4+ T cells and IL-1β/CXCL2) than a direct drug-on-bacteria toxicity mechanism. This is explicitly a reverse-direction, not-harmful finding relative to the "gut microbiome risk" framing of the category.

Counter-evidence held on record

Route matters in the one animal study available: injectable administration did not reproduce the oral effect, meaning the finding may be partly gut-exposure-dependent (first-pass, local GI drug concentration) rather than purely systemic. This is graded yellow, not white, because real Tier B bupropion-specific data exist and animal-only evidence caps it below orange; it should not be marketed as a probiotic-like benefit, since it is a single rodent stress model, not a human finding.

Limits on what this shows

• Key negative/null finding: A 28-day oral 20 mg/kg rat study (bupropion vs. escitalopram vs. control, n=8/group) found hemoglobin and hematocrit significantly higher in the bupropion group than control (Hgb 16.38±0.3 vs 15.63±0.2 g/dL, Hct 46.06±0.9 vs 44.43±0.5%, p<0.05), with no significant RBC-count difference. This is the opposite direction from the postmarketing suppression signal and argues against a routine oxygen-delivery deficit at ordinary dosing.
• At-risk subgroups: Not defined; all identified case reports are isolated, idiosyncratic events without a demonstrated risk factor.

Regulatory status

FDA label, Postmarketing Experience, Hemic and Lymphatic: "ecchymosis, anemia, leukocytosis, leukopenia, lymphadenopathy, pancytopenia, and thrombocytopenia," plus altered PT/INR when coadministered with warfarin.

Population evidence

Case reports: a 55-year-old man developed thrombotic thrombocytopenic purpura (TTP) roughly 54 days after starting bupropion, presenting with diarrhea, acute renal failure, and confusion (Int J Clin Pharmacol Ther, 2013); a separate case of TTP-hemolytic uremic syndrome was reported after bupropion for smoking cessation, described at the time as the first such report (Blood Coagul Fibrinolysis, 2003); a 2024 BMJ Case Reports case of bupropion-induced pancytopenia with rash was indexed in Reactions Weekly (2025). All are single-patient reports with no denominator.

Mechanism

Not established for the hematologic-suppression direction; TTP/HUS case reports invoke an idiosyncratic immune-mediated mechanism typical of drug-associated TTP, not a nutrient-deficiency pathway. Not a nutrient-deficiency-mediated anemia (Hard Rule 2): these are clinical outcomes, named as such.

Counter-evidence held on record

The rat hemoglobin/hematocrit finding is animal-only and does not rule out rare idiosyncratic human hematologic reactions; the two evidence bases describe different phenomena (routine physiological dosing vs. rare idiosyncratic drug reactions) and are not in direct contradiction, but neither should be read as generalizing to the other. Framing caution: unexplained bruising, infection, fatigue, or pallor in a bupropion user warrants a clinical CBC, not a self-directed iron or B12 supplement; nothing here indicates a nutrient-repletion response would address a drug-induced cytopenia.

Limits on what this shows

• Key negative/null finding: The complex-II-linked ATP stimulation is itself a null/counter-finding against a simple "bupropion impairs ATP production" claim, and is recorded as such rather than omitted.

Regulatory status

Not addressed in the FDA label.

Population evidence

Same two Tier B bupropion-specific in vitro sources as Mitochondrial burden: isolated pig brain mitochondria showed complex-II-linked ATP kinetics "significantly stimulated by BUP (105.7±0.4% at 50 µmol/L, p=0.032)" even as complex I and IV activity were each significantly inhibited at 100 µmol/L (Antioxidants, 2023). Primary rat hepatocytes/HepG2 cells showed mitochondrial membrane depolarization at cytotoxic bupropion concentrations, a state generally associated with reduced ATP-synthesis capacity, though ATP was not itself directly quantified in the snippet-level detail retrieved (2017).

Mechanism

Complex-specific: ATP-synthesis capacity via the complex-II/succinate dehydrogenase pathway appears preserved or mildly enhanced at the concentrations tested, while complex I/IV-dependent respiration is impaired; net cellular ATP output under these mixed effects was not directly reported.

Counter-evidence held on record

No study measured whole-cell or whole-body ATP output directly; both supporting studies are proxy measures (electron-transport-chain complex activity, membrane potential) in isolated mitochondria or cultured cells at concentrations above typical plasma levels, not a validated functional ATP marker in a living organism (Hard Rule 3 caution).