Methylene blue is a salt used as a dye and as a medication. It is a formal derivative of phenothiazine and is a dark green powder that yields a blue solution in water. The hydrated form has 3 molecules of water per unit of methylene blue. Here are some of the uses and properties of methylene blue:
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Medication: Methylene blue is used to treat methemoglobinemia, a condition in which the blood loses its ability to carry oxygen. It is also an inhibitor of nitric oxide synthase and guanylate cyclase and has been found to improve the hypotension associated with septic shock.
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Dye: Methylene blue is a dye that behaves as a redox indicator and is commonly used in the food industry to test the freshness of milk and dairy products. It is also used in materials science to reflect the amount of clay minerals in aggregate samples.
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Disinfectant: Methylene blue is a positively charged dye that is inherently attracted to acidic cell components and has been found to be effective in decontaminating SARS-CoV-2 on personal protective equipment.
Some common adverse effects of methylene blue include bluish-green discoloration of urine and limb pain following IV administration. It is contraindicated in patients who have demonstrated hypersensitivities or anaphylaxis after past administration and for those with glucose-6-phosphate dehydrogenase deficiency due to susceptibility of experiencing hemolytic anemia.
