From the Guidelines
Methylene blue is primarily used to treat methemoglobinemia, a condition where blood cannot properly carry oxygen, at doses of 1-2 mg/kg administered intravenously, as recommended by the American Journal of Hematology in 2021 1. The treatment of methemoglobinemia with methylene blue involves administering the medication intravenously over 3 to 5 minutes, with a usual starting dose of 1–2 mg/kg (0.2 mL/kg of a 1% solution) 1. Key points to consider when using methylene blue for this purpose include:
- The dose may be repeated at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes 1
- Methylene blue should reduce MetHb levels significantly in less than an hour 1
- Risk of worsening of methemoglobinemia increases with repeated doses, with toxic levels of MB reached at a total dose > 7 mg/kg 1
- A rebound phenomenon of increased MetHb levels after completion of therapy is attributed to the reversal of the reduction reaction 1 In cases where methemoglobinemia is caused by a long-acting oxidant stress, such as after dapsone ingestion, repeat dosing every 6–8 hours for up to 2–3 days or a continuous IV infusion of 0.10–0.25 mg/kg/hr may be necessary 1.
From the FDA Drug Label
PACKAGE LABEL.PRINCIPAL DISPLAY PANEL NDC 70771-1768-1 Methylene Blue Injection, USP 50 mg/10 mL (5 mg/mL) Intravenous use only Single-Dose vial Rx only NDC 70771-1768-5 Methylene Blue Injection, USP 50 mg/10 mL (5 mg/mL) Intravenous use only 5 X 10 mL Single-Dose Vial Rx only NDC 70771-1767-1 Methylene Blue Injection, USP 10 mg/2 mL (5 mg/mL) Intravenous use only Single-Dose vial Rx only NDC 70771-1767-5 Methylene Blue Injection, USP 10 mg/2 mL (5 mg/mL) Intravenous use only 5 X 2 mL Single-Dose Vial Rx only
The FDA drug label does not answer the question.
From the Research
Uses of Methylene Blue
- Methylene blue is used to treat methemoglobinemia, a disorder characterized by the presence of >1% methemoglobin in the blood 2, 3, 4.
- It acts by providing an artificial electron acceptor for NADPH methemoglobin reductase, which helps to reduce methemoglobin to hemoglobin 2.
- The typical dose of methylene blue for treating methemoglobinemia is 1-2 mg/kg administered slow intravenously 2, 3, 4.
- Methylene blue can also be used to treat refractory hypotension, as seen in a case report where a 22-month-old girl with septic shock was treated with intravenous methylene blue 5.
- Additionally, methylene blue has been explored as a potential treatment for other conditions, but its primary use remains in the treatment of methemoglobinemia.
Important Considerations
- Methylene blue should be used with caution in patients with known or suspected glucose-6-phosphate dehydrogenase (G6PD) deficiency, as it can exacerbate the condition 2, 3, 4.
- The effectiveness of methylene blue can be reduced in the presence of haemolysis, and high doses can even initiate methaemoglobin formation 4.
- Alternative treatments, such as hyperbaric oxygenation monotherapy, may be considered when methylene blue is not available or effective 6.