From the Guidelines
Methylene blue should be administered at a dose of 1-2 mg/kg intravenously to treat methemoglobinemia, with caution in patients with G6PD deficiency, serotonergic medication use, and other specific conditions. The treatment of methemoglobinemia with methylene blue is based on its ability to act as an electron donor, converting methemoglobin back to normal hemoglobin and restoring oxygen-carrying capacity in the blood 1.
Key Considerations
- The usual starting dose is 1–2 mg/kg (0.2 mL/kg of a 1% solution) infused intravenously over 3 to 5 minutes, with the option to repeat the dose at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes 1.
- Patients with G6PD deficiency are at risk for complications, including hemolytic anemia, and should be tested for G6PD deficiency before methylene blue therapy is instituted 1.
- Methylene blue should be used with caution in patients taking serotonergic medications due to the potential for serotonin syndrome 1.
- The medication can cause temporary blue-green discoloration of urine and skin, and careful monitoring is necessary to ensure proper dosing and to watch for potential side effects.
Special Populations
- In patients with continued production of methemoglobin from a long-acting oxidant stress, such as after dapsone ingestion, repeat dosing every 6–8 hours for up to 2–3 days or continuous IV infusion of 0.10–0.25 mg/kg/hr may be necessary 1.
- Methylene blue should be used cautiously in pregnant women, patients with renal failure, and anesthetized patients due to concerns about teratogenicity, potential intestinal atresia, and inhibition of guanylate cyclase leading to systemic and pulmonary hypertension 1.
Dosage and Administration
- The dose may be repeated at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes, with a maximum total dose of 7 mg/kg to avoid toxic levels of methylene blue 1.
- In cases of worsening methemoglobinemia after methylene blue treatment, urgent exchange transfusion should be performed 1. According to the most recent guidelines, methylene blue is recommended as a treatment for methemoglobinemia at a dose of 1-2 mg/kg, with careful consideration of potential risks and interactions 1.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Methylene Blue Uses
- Methylene blue is used to treat methemoglobinemia at a dose of 1 to 2 mg/kg intravenously 2
- It is also used to treat vasoplegic syndrome, ifosfamide-induced encephalopathy, and cyanide intoxication 3, 4
- Methylene blue is used as a diagnostic substance during some diagnostic procedures and to detect leaks or position of parathyroid corpuscles during surgery 3
Methylene Blue Side Effects
- The use of methylene blue can cause dose-dependent toxic effects, including hemolysis, methemoglobinemia, nausea, vomiting, chest pain, dyspnea, and hypertension 3
- Methylene blue can also induce serotoninergic toxicity, which clinically manifests as neuromuscular hyperactivity 3
- Patients with G-6-PD deficiency are at risk of hemolytic effects when treated with methylene blue 2, 5
- Adverse effects attributable to methylene blue were reported in 4.9% of cases, including one instance of hemolysis 5
Methylene Blue Interactions
- Methylene blue can interact with serotonergic medications, leading to serotonin excess syndrome 6
- The use of methylene blue in combination with selective serotonin reuptake inhibitors can be potentially lethal 6
- Patients undergoing cardiopulmonary bypass for cardiac surgery are at risk of postbypass vasoplegic shock and should be aware of the potential interaction between methylene blue and serotonergic medications 6
Methylene Blue Efficacy
- Methylene blue is effective in treating methemoglobinemia, with improvement reported in 98% of cases 5
- A single dose of 1-2 mg/kg of methylene blue is sufficient to treat most patients with methemoglobinemia 5
- Methylene blue is also efficacious in treating ifosfamide neurotoxicity and refractory vasoplegic shock in both pediatric and adult critical care patients 4