Repaglinide

Limits on what this shows

• Why no grade: Both conditions for ungraded were met: no Tier B/C evidence was found linking repaglinide to mitochondrial structure, membrane integrity, electron transport, or biogenesis, and no circulating consumer claim about repaglinide and mitochondrial damage was identified to rebut as white. Search was genuinely multi-phrasing and multi-channel: PubMed searches for "repaglinide mitochondrial KATP channel," "repaglinide ischemic preconditioning OR mitochondrial KATP," and "repaglinide SUR1 SUR2 selectivity cardiac" returned either no repaglinide-specific results or only generic mitochondrial-KATP/ischemic-preconditioning reviews with no repaglinide-specific study among them. The related oxidative-stress evidence (Gumieniczek papers, above) addresses redox markers in cardiac, kidney, liver, and testicular tissue, not mitochondrial structure or biogenesis directly, and is recorded under Oxidative stress rather than here to avoid double counting.

Tooling note

Some PubMed queries during this category's search were also blocked by reCAPTCHA challenges rather than returning clean "no results" pages; the searches that did return clean results (mitochondrial KATP, ischemic preconditioning) genuinely found no repaglinide-specific study, so this is treated as a real evidence gap rather than purely a tooling failure, but a future revision should re-check given the partial blocking.

Limits on what this shows

• Key negative/null findings: Yamazaki et al. 2014 (comparative trial, repaglinide vs glimepiride, 9 patients completing) measured inflammatory and oxidative-stress markers in blood and urine as a head-to-head comparator study; this is an active-comparator design (repaglinide vs another secretagogue, not vs no treatment) and does not establish repaglinide's effect against an untreated baseline.
• At-risk subgroups: Not applicable; this is a protective, not depletive, signal.
• Counter-evidence on record: All animal evidence is in alloxan-induced diabetic rabbits, not humans; the human study (Tankova) is small and does not isolate the antioxidant effect from the drug's primary glucose-lowering action, so confounding by improved glycemic control (rather than a direct pharmacologic antioxidant property) cannot be excluded.

Regulatory status

Not addressed in the FDA label; this is an independent pharmacology literature finding.

Population evidence

Tankova et al. 2003 (Diabetes Research and Clinical Practice, DOI 10.1016/s0168-8227(02)00179-1): a clinical study in type 2 diabetic patients treated with repaglinide reporting improved glycemic control accompanied by a beneficial effect on oxidative-stress markers. Three animal studies by Gumieniczek (alloxan-induced diabetic rabbits, repaglinide-treated): kidney/liver oxidative stress (Acta Diabetologica 2005, DOI 10.1007/s00592-005-0182-2) found diminished lipid peroxidation in diabetic kidney with repaglinide treatment; cardiac oxidative stress (Life Sciences 2005, DOI 10.1016/j.lfs.2005.04.074) examined cardiac superoxide dismutase and related antioxidant enzyme changes; testicular oxidative stress (Open Life Sciences 2007, DOI 10.2478/s11535-007-0034-x) examined the same in testicular tissue. A separate rat study (PMID 27635199) found repaglinide (0.2-0.4 mg/kg) reversed cyclosporine-A-induced increases in malondialdehyde and decreases in superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, and total glutathione in kidney tissue.

Mechanism

Not a classical nutrient-sparing mechanism; proposed as a direct antioxidant/free-radical-scavenging property of the repaglinide molecule and/or an indirect effect of improved glycemic control reducing hyperglycemia-driven oxidative stress. Mechanism is not fully isolated from the glucose-lowering effect in the cited sources.

Counter-evidence held on record

This finding runs opposite to a "depletion" narrative and must never be used to suggest antioxidant supplementation is needed on repaglinide, or that repaglinide itself substitutes for dietary antioxidant intake. It is provided as context only: the available evidence does not support a repaglinide-associated oxidative-stress burden.

Limits on what this shows

• Why no grade: A PubMed search for "repaglinide copper" returned a clean, explicit "no results were found" (not a bot block), and no circulating consumer claim linking repaglinide to copper status was identified in the searches conducted for this review. Both conditions for ungraded are met.

Tooling note

None; this search returned a genuine, clean null result.

Limits on what this shows

• Why no grade: A PubMed search for "repaglinide AND (iron OR ferritin OR hemoglobin)" returned 149 results, but review of the top results found they were matched on "hemoglobin" in the sense of glycosylated hemoglobin (HbA1c, a glucose-control marker), not iron status, ferritin, or hemoglobin as an oxygen-carrying measure; none of the returned titles addressed iron metabolism or iron-deficiency anemia specifically. No circulating consumer claim linking repaglinide to iron status was identified. Both conditions for ungraded are met.

Tooling note

An earlier, narrower search ("repaglinide iron") returned only page metadata rather than confirmed search content, so this entry rests on the broader, successfully returned search described above rather than that first attempt.

Limits on what this shows

• Key negative/null findings: Not accessible; see access note below.
• At-risk subgroups: Not accessible; see access note below.
• Counter-evidence on record: Not accessible; see access note below.

Regulatory status

Not addressed in the FDA label.

Population evidence

"Effects of metformin, saxagliptin and repaglinide on gut microbiota in high-fat diet/streptozocin-induced type 2 diabetic mice," BMJ Open Diabetes Research & Care, 2024, DOI 10.1136/bmjdrc-2023-003837 (PMID 38719505). The title and Crossref bibliographic record confirm repaglinide was one of three drug arms studied (alongside metformin and saxagliptin) against a diabetic control in a mouse model, specifically examining gut microbiota effects.

Mechanism

Not confirmed for this specific study; plausible mechanisms for antidiabetic-agent effects on gut microbiota in general include altered glucose availability to colonic bacteria and altered gut transit/motility, but this dossier could not confirm which, if any, of these were invoked for repaglinide specifically.

Counter-evidence held on record

Full text of this study was attempted via PubMed, PubMed Central, Europe PMC, and the publisher (BMJ) directly; all four attempts were blocked by bot-verification challenges or rate limiting rather than returning content. Only the bibliographic record (title, DOI, journal, year, and the three-arm design implied by the title) could be confirmed via the Crossref API. This entry is graded yellow on the strength of the confirmed drug-specific study design alone; the direction and magnitude of any microbiota change are not stated here because they could not be verified, and should be re-checked in a future revision when full-text access is available.

Limits on what this shows

• Key negative/null findings: The 12-24 week pivotal clinical trials summarized in the label do not report hemoglobin or hematocrit changes as an adverse finding; hemolytic anemia only appears in the postmarketing section, consistent with a low-frequency signal not captured in premarketing trial sample sizes.
• At-risk subgroups: Not specified in the label; general pharmacovigilance principle is that idiosyncratic hemolysis can occur in patients with underlying G6PD deficiency or other predisposing hematologic conditions, though this is not stated specifically for repaglinide.
• Counter-evidence on record: No hemoglobin/hematocrit signal appears in controlled trial data; this is a rare postmarketing report, not a reproducible controlled finding.

Regulatory status

Listed in the U.S. Prandin (repaglinide) label under postmarketing experience, alongside severe hepatic dysfunction including jaundice and hepatitis. Clinical-trial-era laboratory findings (<1% incidence) separately list elevated liver enzymes, thrombocytopenia, leukopenia, and anaphylactoid reactions, but not hemolytic anemia specifically; hemolytic anemia is a postmarketing-only signal.

Population evidence

Postmarketing pharmacovigilance reporting (spontaneous adverse-event reports), not a controlled incidence study; no denominator or rate is given in the label.

Mechanism

Not specified in the label. Postmarketing hemolytic anemia associated with oral antidiabetic agents is most often idiosyncratic/immune-mediated rather than a nutrient-deficiency (e.g., iron, B12, or folate) hemolysis; no iron, B12, or folate deficiency mechanism is described in the source.

Counter-evidence held on record

This is a drug safety outcome, not a nutrient deficiency, and is not evidence that repaglinide causes iron, B12, or folate deficiency. It should be framed to a reader as "rare drug-induced blood-cell effect to be aware of," not as a reason to supplement any hematinic nutrient. Unexplained fatigue, pallor, or jaundice in a patient on repaglinide warrants a clinician-ordered CBC, not self-directed supplementation.

Limits on what this shows

• Key negative/null findings: The same review notes that despite this in vitro signal, the FDA Adverse Event Reporting System shows minimal human cases of muscle atrophy attributable to glinides or sulfonylureas, and concludes current evidence is insufficient to support clinical recommendations or prohibitions.
• At-risk subgroups: Not established clinically; the source discusses this as a theoretical concern for frail or sarcopenic older adults on long-term secretagogue therapy, not a confirmed clinical risk group.
• Counter-evidence on record: DrugBank's pharmacology summary for repaglinide states the drug "appears to be selective for pancreatic beta cells and does not appear to affect skeletal or cardiac muscle or thyroid tissue," directly conflicting with the ex vivo finding above. This conflict is disclosed rather than resolved; the ex vivo result is a laboratory/mechanistic finding, and the tissue-selectivity claim appears to reflect the drug's primary intended pharmacology rather than a systematic muscle-tissue study.

Regulatory status

Not addressed in the FDA label.

Population evidence

Mele A et al., "Database search of spontaneous reports and pharmacological investigations on the sulfonylureas and glinides-induced atrophy in skeletal muscle," Pharmacology Research & Perspectives, 2014 (DOI 10.1002/prp2.28). Ex vivo incubation of isolated mouse flexor digitorum brevis muscle for 24 hours found a potency ranking for muscle protein reduction of repaglinide ≥ glibenclamide > glimepiride > tolbutamide > nateglinide, i.e., repaglinide was among the most potent KATP-channel-blocking secretagogues tested for this effect, reviewed and cited in Wu CN, Tien KJ, Journal of Diabetes Research 2020;2020:9368583.

Mechanism

Named: blockade of the sarcolemmal/skeletal-muscle KATP channel (the same ATP-sensing channel class repaglinide targets on pancreatic beta cells) is proposed to activate caspase-3-dependent and -independent skeletal muscle atrophy pathways, an off-target effect distinct from the drug's intended pancreatic action.

Counter-evidence held on record

This is a mechanism-level, ex vivo laboratory finding with directly conflicting tissue-selectivity data and minimal human case evidence. It should not be presented to a consumer as an established clinical risk, and no supplement or dosing action follows from it.