Positives

• In an Alzheimer's mouse model, animals receiving an intranasal methylene blue hydrogel showed restored mitochondrial function and reduced tau-driven cognitive decline, suggesting the brain-targeted route a patient hopes will reach long COVID neurons PubMed.
  
  
• Rats subjected to exhaustive exercise showed neuroprotection against oxidative damage when methylene blue was delivered intranasally rather than systemically PMC.
  
  

Negatives

• A patient on an SSRI or SNRI is at high risk of serotonin syndrome because methylene blue is a potent MAO-A inhibitor, with case reports of tremor, hyperthermia, and confusion PMC.
  
  
• A patient should know that no high-quality human evidence supports methylene blue for brain fog and FDA has not approved it for cognitive enhancement APSF.
  
  

Hurdles & Side Effects

• A patient must locate a compounding pharmacy that uses USP pharmaceutical-grade rather than industrial methylene blue, since the chemical-grade product carries heavy-metal contamination risk PMC.
  
  
• A patient stopping serotonergic antidepressants for safe dosing faces a long washout window, often weeks, before methylene blue can be safely introduced APSF.