Methylene Blue Injection is a prescription drug used in the treatment of Methaemoglobinaemia. Its active ingredient is methylene blue trihydrate (3,7-Bis(dimethylamino)phenazathionium chloride trihydrate).
In patients with methaemoglobinaemia, therapeutic doses of methylene blue can lower the levels of methaemoglobin in red blood cells. It activates a normally dormant reductase enzyme system that reduces the methylene blue to leucomethylene blue, which in turn is able to reduce methaemoglobin to haemoglobin. However, in large doses, methylene blue can itself produce methaemoglobinaemia and the methaemoglobin concentration should therefore be closely monitored during treatment. Methylene blue is not effective for the treatment of methaemoglobinaemia in patients with glucose-6-phosphate dehydrogenase deficiency as these patients have a diminished capacity to reduce methylene blue to leucomethylene blue. It is also potentially harmful as patients with glucose-6-phosphate dehydrogenase deficiency are particularly susceptible to the haemolytic anaemias induced by methylene blue.
Methylene Blue Solution for Injection is indicated:
For the treatment of drug-induced methaemoglobinaemia
For the treatment of idiopathic methaemoglobinaemia (in which a structural
abnormality of haemoglobin is not present)
As a bacteriological stain
As a dye in diagnostic procedures such as fistula detection
For the delineation of certain body tissues during surgery.