Methylene blue is a phenothiazine dye and the first fully synthetic drug. At low doses, it acts as an alternative electron carrier in the mitochondrial electron transport chain.
Mechanism — Accepts electrons from NADH and donates to cytochrome c, bypassing damaged complex I/III. Inhibits NOS-derived peroxynitrite. Mild MAOI activity. Net effect: cellular energy support, neuroprotection, and antioxidant action.
Use case — Low-dose (0.5-4 mg/day) for cognitive support, mitochondrial dysfunction, brain fog after illness. Pharmaceutical-grade only — aquarium-grade contains heavy metal contaminants.
Caveats — Stains everything blue (mouth, urine). MAOI interaction is real — don't combine with serotonergic drugs (SSRIs, MDMA, 5-HTP). High doses (>5 mg/kg) become a pro-oxidant. G6PD deficiency is a contraindication.