Methylene blue


Adult Dosing

  • Acquired methemoglobinemia: 1 mg/kg IV over 5-30min, may repeat in 1h with up to 1 mg/kg IV if methemoglobin level still >30% or symptoms persist
  • Drug-induced methemoglobinemia: 1-2 mg/kg IV slowly over several minutes
  • See vasopressors
    • For hypotension refractory to catecholamine pressors
    • Consider after catecholamine, vasopressin, and mineralocorticoid refractive shock

Pediatric Dosing

  • Same as weight-based adult dosing

Special Populations

  • Pregnancy Rating: X, Fetal risk has been demonstrated
  • Lactation risk: Infant risk cannot be ruled out
  • Renal dosing: no adjustment
  • Hepatic dosing: no adjustment


Adverse Reactions


  • Hemolytic anemia
  • Syncope
  • Serotonin syndrome
  • Paradoxical methemoglobinemia at doses > 4 mg/kg/hr or per bolus
  • Pulmonary vasoconstriction at 3-4 mg/kg/hr or per bolus


  • Skin discoloration, urine discoloration, hyperhidrosis
  • Nausea, abnormal taste
  • Limb pain
  • Dizziness, headache


  • Half-life: 24h
  • Metabolism: Hepatic
  • Excretion: Mostly renal

Mechanism of Action

  • Promotes non-enzymatic redox conversion of methemoglobin to hemoglobin


See Also


  1. Pasin L et al. Methylene blue as a vasopressor: a meta-analysis of randomised trials. Crit Care Resusc. 2013 Mar;15(1):42-8.