Methylene Blue

What it is and how it works

Mechanism of Action Methylene blue is a water soluble thiazine dye that promotes a non-enzymatic redox conversion of metHb to hemoglobin. In situ, methylene blue is first converted to leucomethylene blue (LMB) via NADPH reductase. It is the LMB molecule which then reduces the ferric iron of metHb to the ferrous state of normal hemoglobin.

Indications

1. INDICATIONS AND USAGE Methylene blue injection is indicated for the treatment of pediatric and adult patients with acquired methemoglobinemia. Methylene blue injection (methylene blue) is an oxidation-reduction agent indicated for the treatment of pediatric and adult patients with acquired methemoglobinemia.

Dosage and administration (summary)

2. DOSAGE AND ADMINISTRATION Administer 1 mg/kg intravenously over 5-30 minutes. If methemoglobin level remains above 30% or if clinical symptoms persist, give a repeat dose of up to 1 mg/kg one hour after the first dose. Administer a single dose of 1 mg/kg in patients with moderate or severe renal impairment. Dosage and Administration Ensure patent venous access prior to administration of methylene blue injection. Do not administer methylene blue injection subcutaneously. Administer methylene blue injection 1 mg/kg intravenously over 5-30 minutes.

Contraindications

4. CONTRAINDICATIONS Methylene blue injection is contraindicated in the following conditions: Severe hypersensitivity reactions to methylene blue or any other thiazine dye . Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia Methylene blue injection is contraindicated in the following conditions : Severe hypersensitivity to methylene blue Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia

Warnings and precautions

5. WARNINGS AND PRECAUTIONS Hypersensitivity: If severe or life-threatening allergic reaction occurs, discontinue Methylene blue injection, treat the allergic reaction, and monitor until signs and symptoms resolve Lack of Effectiveness: Consider alternative treatments if there is no resolution of methemoglobinemia after 2 doses ( 2.1 , 5.3 ) Hemolytic Anemia: Discontinue Methylene blue injection and transfuse Interference with In-Vivo Monitoring Devices: Use methods other than pulse oximetry to assess oxygen saturation Effects on Ability to Drive and Operate Machinery: Advise patients to refra…

Pregnancy

Pregnancy Risk Summary Methylene blue injection may cause fetal harm when administered to a pregnant woman. Intra-amniotic injection of pregnant women with a methylene blue class product during the second trimester was associated with neonatal intestinal atresia and fetal death.

Storage and supply

16. HOW SUPPLIED/STORAGE AND HANDLING Methylene blue injection, USP: is supplied in 10 mL single-dose vials. Each 10 mL vial contains 50 mg of methylene blue as a clear dark blue solution. A box contains five vials. Box of 5 vials of 50 mg/10 mL (0.5%): NDC 82432-104-02 Storage: Store at 20°C to 25°C (68°F to 77°F).

Source: Methylene Blue (Methylene Blue) — US FDA prescribing information, 2026-01-28, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.