How to prescribe methylene blue?

From the Guidelines

Methylene blue should be prescribed at a dose of 1-2 mg/kg intravenously over 3 to 5 minutes as the first-line treatment for symptomatic methemoglobinemia with a high MetHb level, defined as more than 10%-30% 1.

Important Considerations

• 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.
• Patients with continued production of MetHb from a long-acting oxidant stress may require repeat dosing every 6-8 hours for up to 2-3 days or MB may be given as a continuous IV infusion of 0.10-0.25 mg/kg/hr 1.

Special Populations

• Methylene blue should be avoided in patients with G6PD deficiency due to the risk of hemolysis and worsening methemoglobinemia 1.
• Methylene blue should be used with caution in pregnant women due to concerns about teratogenicity and possible intestinal atresia 1.
• Methylene blue should be used cautiously in patients with renal failure and in anesthetized patients where it may inhibit guanylate cyclase, decreasing nitric oxide-mediated vasodilatation leading to systemic and pulmonary hypertension 1.

Additional Treatments

• Ascorbic acid can be given orally, intramuscularly, or IV in addition to methylene blue treatment 1.
• Therapeutic whole blood exchange (TWBE) or hyperbaric oxygen therapy should be considered if there is no improvement with the use of repeated doses of MB 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

Prescribing Methylene Blue

To prescribe methylene blue, consider the following:

• The dosage for treating methemoglobinemia is 1 to 2 mg/kg intravenously 2
• Methylene blue is generally safe but may cause dose-related hemolytic effects 2
• Special caution is needed when treating patients with G-6-PD deficiency, as methylene blue can increase the risk of hemolysis through oxidative stress 3, 2

Administration Considerations

• Methylene blue can be administered as a bolus or continuous infusion 4
• Bolus administration may increase pulmonary vascular resistance, while continuous infusion may avoid this effect 4
• The drug's pharmacologic actions, dosing, and adverse effects should be carefully considered 5

Patient-Specific Considerations

• Patients with G-6-PD deficiency may require alternative treatments, such as leucomethylene blue, which may be safer and more effective 3
• Patients exposed to aniline dyes and dapsone may also present special risks in the treatment of methemoglobinemia 2