Methylene blue

Methylene blue (CI 52015) is a heterocyclic aromatic chemical compound with the chemical formula C₁₆H₁₈N₃SCl. It has many uses in biology and chemistry; for example, it can be used as a stain and as a pharmaceutical drug. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in water. The hydrated form has 3 molecules of water per unit of methylene blue. Methylene blue should not be confused with methyl blue, another histology stain, new methylene blue, nor with the methyl violets often used as pH indicators.

The International Nonproprietary Name (INN) of methylene blue is methylthioninium chloride.

Methylene blue was first prepared in 1876 by German chemist Heinrich Caro (1834-1910). It is on the World Health Organization's List of Essential Medicines, a list of the most important medications needed in a basic health system.

Medical uses

Methylene blue is a component of a frequently prescribed urinary analgesic/anti-infective/anti-spasmodic known as "Prosed", a combination of drugs which also contains phenyl salicylate, benzoic acid, hyoscyamine sulfate, and methenamine (aka hexamethylenetetramine and not to be confused with 'methanamine').