What is the appropriate dosing for Methylene Blue (methylthioninium chloride)?

From the Guidelines

Methylene Blue should be dosed at 1–2 mg/kg (0.2 mL/kg of a 1% solution) infused intravenously over 3 to 5 minutes for the treatment of methemoglobinemia. This dosing recommendation is based on the most recent and highest quality study available, which was published in the American Journal of Hematology in 2021 1. The dose may be repeated at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes. However, it is crucial to note that the risk of worsening of methemoglobinemia increases with repeated doses, with toxic levels of Methylene Blue reached at a total dose > 7 mg/kg 1.

Some key points to consider when dosing Methylene Blue include:

• The dose should not exceed 7 mg/kg to avoid toxic levels 1
• Patients with continued production of methemoglobinemia from a long-acting oxidant stress may require 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 1
• Methylene Blue should reduce methemoglobin levels significantly in less than an hour, and a rebound phenomenon of increased methemoglobinemia levels after completion of therapy may occur 1

It is essential to carefully monitor patients receiving Methylene Blue and adjust the dosing regimen as needed to minimize the risk of adverse effects and ensure effective treatment of methemoglobinemia. In cases of worsening methemoglobinemia after Methylene Blue treatment, urgent exchange transfusion should be performed 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 appropriate dosing for Methylene Blue (methylthioninium chloride) is not explicitly stated in the provided text. The text only provides information about the available formulations and concentrations of the drug, but does not specify the recommended dose. 2

From the Research

Dosing for Methylene Blue

The appropriate dosing for Methylene Blue (methylthioninium chloride) varies depending on the condition being treated.

• For methemoglobinemia, the dose is typically 1 to 2 mg/kg intravenously 3, 4.
• In cases of refractory shock resulting from drug poisoning, a loading dose of 1.5 mg/kg and continuous infusion (1.5 mg/kg/h for 12 h, then 0.75 mg/kg/h for 12 h) has been used 5.
• For other conditions, such as vasoplegia and as an aid to parathyroidectomy, doses of 1-7.5 mg kg(-1) have been used 6.
• In cases of pharmacologically induced shock, bolus doses ranging from 1 to 3 mg/kg, with repeat boluses or maintenance infusions, have been reported 7.

Special Considerations

• Patients with G-6-PD deficiency may be at risk for hemolytic effects and should be treated with caution 3, 4.
• Methylene blue is less effective or ineffective in the presence of glucose-6-phosphate dehydrogenase deficiency, and high dose methylene blue can itself initiate methaemoglobin formation in the presence of haemolysis 4.
• The dose of methylene blue should be carefully considered in patients taking serotonin reuptake inhibitors, as it can precipitate serotonin toxicity 6.