From the Guidelines
Methylene blue is the primary treatment for decreasing methemoglobin levels, and it should be administered at a starting dose of 1–2 mg/kg intravenously over 3 to 5 minutes. This 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 study highlights the importance of methylene blue in treating methemoglobinemia, a condition where blood cannot effectively carry oxygen.
Key Points to Consider
- The dose of methylene blue may be repeated at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes 1.
- 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.
- In cases of worsening methemoglobinemia after methylene blue treatment, urgent exchange transfusion should be performed 1.
- For 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 a continuous IV infusion of 0.10–0.25 mg/kg/hr may be necessary 1.
Important Considerations for Treatment
- Methylene blue should reduce methemoglobin levels significantly in less than an hour 1.
- A rebound phenomenon of increased methemoglobin levels after completion of therapy is attributed to the reversal of the reduction reaction 1.
- The medication works by accepting an electron from NADPH and reducing the 3+ ferric state back to the 2+ ferrous state in erythrocytes 1.
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 as a treatment for ifosfamide-induced encephalopathy, with some studies showing its effectiveness in preventing or reversing the condition 3, 4, 5
- Additionally, methylene blue has been used to treat refractory vasoplegic shock in both pediatric and adult critical care patients 5
- It has also been proposed as a potential adjunct in the treatment of septic shock, anaphylactic shock, and toxin-induced shock 6
Methylene Blue Mechanism of Action
- Methylene blue's mechanism of action is based partly on its oxidizing capabilities, which can help reduce methemoglobin to hemoglobin 2, 5
- It can also interfere with guanylate cyclase activity, preventing cyclic guanosine monophosphate production and vasodilatation, which can help increase blood pressure in shock states 6
Methylene Blue Administration and Dosage
- Methylene blue can be administered intravenously, with dosages ranging from 1 to 2 mg/kg for methemoglobinemia treatment 2
- For ifosfamide-induced encephalopathy, methylene blue has been administered at a dose of 50 mg intravenously every 6 hours 3
- The optimal dosage and administration schedule for methylene blue in other conditions, such as shock states, may vary and require further study 6