From the Guidelines
Methylene Blue is a synthetic basic dye used to treat methemoglobinemia by reducing ferric iron in hemoglobin to ferrous iron, with a recommended dosage of 1-2 mg/kg administered intravenously over 3 to 5 minutes, as supported by the most recent guidelines 1. The medication works by accepting an electron from NADPH and reducing the 3+ ferric state back to the 2+ ferrous state in erythrocytes, as described in the American Journal of Hematology study 1. Some key points to consider when using Methylene Blue include:
- The dose may be repeated at 1 mg/kg if methemoglobinemia does not significantly decrease within 30–60 minutes, but risk of worsening of methemoglobinemia increases with repeated doses 1.
- Methylene Blue should reduce MetHb levels significantly in less than an hour, and a rebound phenomenon of increased MetHb levels after completion of therapy is attributed to the reversal of the reduction reaction 1.
- In cases of worsening methemoglobinemia after MB treatment, urgent exchange transfusion should be performed, as recommended by the 2023 American Heart Association guidelines 1. It's also important to note that Methylene Blue has antimicrobial properties and can be used in certain infections, but side effects may include blue discoloration of urine and skin, nausea, vomiting, and in rare cases, serotonin syndrome when combined with certain medications. As supported by the highest quality and most recent study 1, the use of Methylene Blue is recommended for the treatment of methemoglobinemia, with exchange transfusion and hyperbaric oxygen therapy considered as alternative treatments in cases where Methylene Blue is not effective.
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
Methylene Blue is an injection, as indicated by the label, for Intravenous use only. The provided text does not explicitly define what Methylene Blue is, but it does describe it as Methylene Blue Injection, USP. 2
From the Research
Definition and Uses of Methylene Blue
- Methylene blue is a drug used for various conditions, including intravenously in methemoglobinemia, vasoplegia, and as an aid to parathyroidectomy 3
- It is also used to treat ifosfamide-induced encephalopathy, fosfamide-induced encephalopathy, and cyanide intoxication 4
- Methylene blue has been used as a diagnostic substance during some diagnostic procedures and as a part of the treatment of several diseases 4
Mechanism of Action and Interactions
- Methylene blue inhibits monoamine oxidase-A, which can lead to serotonin excess syndrome when given in combination with serotonergic medications 5
- The interaction between methylene blue and serotonin reuptake inhibitors can precipitate serotonin toxicity, which has important preventative and treatment implications 3
- The use of methylene blue should be weighed in light of current medications and potential drug interactions, especially in patients undergoing cardiopulmonary bypass for cardiac surgery 5
Adverse Effects and Risks
- Methylene blue can cause severe central nervous system toxicity, including serotonin toxicity 3
- The toxic effects of methylene blue are dose-dependent and include serious symptoms such as hemolysis, methemoglobinemia, nausea, vomiting, chest pain, dyspnea, and hypertension 4
- Methylene blue-induced serotoninergic toxicity clinically manifests as neuromuscular hyperactivity 4
- Alternative treatments, such as ascorbic acid, may be used instead of methylene blue in patients at risk of serotonin syndrome 6