Methylene Blue
/ Phenothiazine dye (small molecule); mitochondrial alternative electron carrier; MAO inhibitor at high dosesALIAS · Methylthioninium chloride · Methylene blue · Provayblue (trade)
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Tier 1 for the FDA-approved methemoglobinemia indication. Methylene blue (methylthioninium chloride) has been an approved drug for decades; Provayblue received contemporary FDA approval (2016) for acquired methemoglobinemia. Geroscience and Alzheimer-related Phase 2 trials (TauRx LMTM — leucomethylthioninium, a derivative — Wischik and colleagues) sit alongside the approved indication; the cognitive enhancement and longevity framing in vendor channels substantially exceeds the controlled-trial evidence base.
Methylene blue (3,7-bis(dimethylamino)phenothiazine-5-ium chloride) is a heterocyclic phenothiazine dye with a redox-active phenothiazine ring that cycles between the oxidised (blue) MB+ and reduced (colourless) leucomethylene blue (MBH2) forms. The molecule accepts electrons from NADH and NADPH and donates them to oxygen or to downstream electron acceptors, enabling methylene blue to function as an alternative mitochondrial electron carrier — a property that underlies both its methemoglobinemia indication (reducing ferric to ferrous haem) and its preclinical mitochondrial bioenergetic literature.
At low concentrations methylene blue accelerates mitochondrial respiration; at higher concentrations it inhibits respiration through electron transport chain disruption, producing a bell-shaped dose-response that complicates clinical translation. Methylene blue is also a reversible monoamine oxidase A inhibitor at therapeutically relevant doses, which carries the principal drug-interaction concern: co-administration with serotonergic agents (SSRIs, SNRIs, MAOIs, certain opioids) has produced serotonin syndrome, including reported fatalities. The approved labelling carries explicit MAO-inhibitor and serotonin syndrome warnings.
Tier 1 for methemoglobinemia. Provayblue approval (2016) was based on demonstration of methemoglobin reduction in acquired methemoglobinemia. Geroscience/cognitive use rests on smaller mechanistic and Phase 2 datasets: Atamna and colleagues (2008) reported methylene blue extended cellular lifespan and improved mitochondrial function in cell models; the TauRx LMTM Phase 2 trial in Alzheimer disease (Wischik and colleagues 2015) evaluated leucomethylthioninium (a structurally related but distinct compound) and produced cognitive endpoint signals that have been the subject of substantial methodological debate.
The principal active concern is serotonin syndrome from MAO inhibition when combined with serotonergic agents — multiple reported cases including fatalities led to specific FDA label warnings. Other adverse events include skin and urine discoloration (blue staining is expected and generally cosmetic), haemolysis in glucose-6-phosphate dehydrogenase deficiency, and methemoglobinemia paradoxically at very high doses. Vendor-grade methylene blue (sold as a 'mitochondrial' or 'cognitive' supplement) lacks the purity and identity assurance of the pharmaceutical-grade Provayblue product; industrial-grade material may contain heavy-metal contaminants.
Regulatory status
- FDA status:
- FDA-approved
- Compounding:
- Not eligible for compounding (approved, not in shortage)
The TauRx LMTM Alzheimer programme is the highest-profile geroscience-adjacent translation of the methylene-blue family, but LMTM is leucomethylthioninium — a structurally distinct compound — and the Phase 2 and subsequent trials have not produced an FDA approval. The 'methylene blue for cognitive enhancement' literature in healthy adults consists of small mechanistic and short-term studies; long-term outcome trials have not been performed. The serotonin syndrome interaction with common antidepressants is the most clinically actionable safety concern in any consumer use case.