Glyburide

Limits on what this shows

• Key negative/null findings: Typical human therapeutic plasma glyburide concentrations are roughly 0.1-0.3 μM at standard oral doses, well below the 50-500 μM range tested; no human or whole-animal in vivo mitochondrial-function data were located.
• At-risk subgroups: Theoretical only: patients with renal or hepatic impairment, in whom the label documents elevated glyburide blood levels, could in principle approach higher local drug concentrations, but this has not been directly measured or demonstrated.

Population evidence

Engbersen R, Masereeuw R, van Gestel MA, et al. Br J Pharmacol. 2005;145(8):1069-1075. In vitro, isolated rat renal mitochondria and freshly isolated proximal tubular cells (animal model, not human). Glibenclamide 50 μM and 100 μM decreased intracellular ATP by 28±4% and 53±5% respectively; the drug inhibited ADP-stimulated respiration and showed dinitrophenol-like uncoupling across a 1-500 μM concentration range.

Mechanism

Named: interference with oxidative phosphorylation, consistent with mitochondrial substrate-transport disruption and ATP synthase reversal, at the concentrations tested.

Counter-evidence held on record

This is mechanistic, animal/in vitro evidence at concentrations far exceeding usual clinical exposure. It should not be read as evidence of mitochondrial toxicity at standard oral dosing in humans, and does not support a supplement or monitoring recommendation on its own.

Limits on what this shows

• Key negative/null findings: Effect was tissue-selective: renal antioxidant enzymes were unchanged in the Elmali study, and brain catalase/GPx were unchanged in the Nazaroglu study, arguing against a uniform, drug-intrinsic antioxidant effect.

Population evidence

Nazaroglu NK, Sepici-Dincel A, Altan N. J Diabetes Complications. 2009;23:209-213. Rat brain tissue: diabetic rats had significantly reduced SOD activity vs. controls (P<0.001); 4 weeks of glyburide treatment restored SOD activity (P<0.05). Brain catalase and glutathione peroxidase were not significantly altered by diabetes or by treatment. Separately: Elmali E, Altan N, Bukan N. Drugs R D. 2004;5(4):203-208. Rat liver and kidney: diabetic rats had significantly reduced hepatic catalase and SOD (P<0.05 both); 5 weeks of glibenclamide treatment restored hepatic enzyme activity. Renal catalase and SOD were unchanged by either diabetes or the drug.

Mechanism

Not a direct antioxidant action of glyburide. Both studies report concurrent normalization of blood glucose alongside enzyme restoration, consistent with an indirect, glycemic-control-mediated effect rather than an independent pharmacologic antioxidant property.

Counter-evidence held on record

Neither study included a non-diabetic, glyburide-treated comparison arm, so an antioxidant effect independent of glucose-lowering cannot be confirmed; both are animal-only, and the two papers share an overlapping author (Altan N) and experimental paradigm, so they should be read as a coherent research program rather than fully independent replications (see Overlap map). This is a reverse-direction finding: it argues against an oxidative-stress-depletion effect from glyburide, not for one. It should not be presented to consumers as a reason to add antioxidant supplements, and it does not establish a human antioxidant benefit either.

Limits on what this shows

• Why no grade: General type 2 diabetes population studies of copper, zinc, and iron alterations correlating with HbA1c were found, but none used glyburide, glibenclamide, or sulfonylureas as a studied exposure variable, so they fail the cohort test and cannot support even a Tier C grade. No Tier D consumer claim linking glyburide to copper was found either, so the white/fails-verification path does not apply. Both conditions for ungraded are met.

Search channels tried

DailyMed label (no mineral section), FDA label, NCBI Bookshelf StatPearls glyburide chapter (no mention of copper anywhere in the chapter), and multi-phrasing general literature search. Direct queries to the Europe PMC REST API and the Semantic Scholar Graph API for glyburide-and-copper were attempted but returned repeated HTTP 429 rate-limit responses during this review and could not be completed; the Crossref API and general search engines were blocked for automated fetch by robots.txt restrictions.

Limits on what this shows

• Why no grade: General type 2 diabetes population studies of serum ferritin and iron status were found in abundance, but none stratified by antidiabetic drug class or named glyburide as an exposure, so none passes the cohort test for this drug. No Tier D consumer claim was found either. Both ungraded conditions are met. (Note: the G6PD-related hemolysis entry under Oxygen delivery/utilization is a distinct, drug-labeled clinical outcome in a genetic subgroup, and is not iron-deficiency evidence; it is graded separately above.)

Search channels tried

DailyMed label, FDA label, NCBI Bookshelf StatPearls glyburide chapter (no mention of iron), and multi-phrasing literature search. As with copper, Europe PMC and Semantic Scholar API queries specific to glyburide-and-iron were attempted and blocked by repeated rate-limiting during this review.

Limits on what this shows

• Why no grade: Liu J-H, Meng Q-Y, Chen Y, et al. Environ Sci Pollut Res. 2023;30:121196-121206. Low-level environmental glibenclamide exposure in Pelophylax nigromaculatus (Asian bullfrog) tadpoles over 30 days: Firmicutes relative abundance decreased, some potentially harmful genera (Clostridium, Bilophila, Hafnia) decreased, beneficial genera (Akkermansia, Faecalibacterium) increased, and overall diversity showed a non-significant downward trend; the authors concluded low-level exposure "did not necessarily exert an adverse impact." Because this is a non-mammalian species under environmental rather than therapeutic dosing, it does not establish human mechanistic plausibility either for or against a risk, so it is not treated as usable Tier B support for a color grade. No circulating consumer claim specific to glyburide and the microbiome was located to rebut as white. Both ungraded conditions are met.
• Tooling limitation disclosed: Candidate class-level review articles on antidiabetic drugs and the gut microbiome (titles located via search, including two PMC review articles) could not be opened during this review: PMC repeatedly returned an automated bot-verification (reCAPTCHA) interstitial instead of article content, and separate Europe PMC REST API queries failed with repeated HTTP 429 rate-limiting. This is a genuine access gap at the time of writing, not a confirmed absence of class-level literature, and a future revision should re-attempt these specific sources.

Limits on what this shows

• At-risk subgroups: G6PD deficiency (X-linked; higher prevalence in patients of African, Mediterranean, Middle Eastern, and Southeast Asian ancestry).

Regulatory status

FDA and DailyMed labeling state directly: "Treatment of patients with glucose 6-phosphate dehydrogenase (G6PD) deficiency with sulfonylurea agents can lead to hemolytic anemia," and note hemolytic anemia has also been reported in patients without known G6PD deficiency.

Population evidence

Class-level regulatory labeling (Tier A) and postmarketing pharmacovigilance; no incidence rate or denominator was located for glyburide specifically during this review.

Mechanism

Named: G6PD-deficient red cells cannot adequately neutralize oxidative stress; sulfonylureas, structurally related to sulfonamides, can act as an oxidant stressor that precipitates hemolysis in these cells.

Counter-evidence held on record

This is a clinical outcome (hemolytic anemia) in a genetically defined subgroup, named as such per Hard Rule 2, not an iron- or B12-deficiency claim, and it is not remedied by iron or B12 supplementation. Overall population risk is low; the relevant response is screening for G6PD status in at-risk ancestries before initiation and prompt discontinuation if hemolysis occurs, both a prescriber decision.

Limits on what this shows

• Key negative/null findings: Concentrations tested (50-100 μM for the ATP endpoint) are far above typical human therapeutic plasma glyburide levels; no in vivo or human ATP/energy-metabolism data were located.

Population evidence

Engbersen R, Masereeuw R, van Gestel MA, et al. Br J Pharmacol. 2005;145(8):1069-1075. Same in vitro rat kidney model as above.

Mechanism

Named: ATP depletion attributed to oxidative-phosphorylation uncoupling and inhibited ADP-stimulated respiration at the tested concentrations.

Counter-evidence held on record

As with mitochondrial burden above, this is concentration-dependent, non-clinical evidence only. A reader should not count this and the mitochondrial burden entry as two independent lines of confirmation; both rest on the same single study (see Overlap map).