Methylthioninium, commonly known as methylene blue, is a synthetic thiazine dye with important medical and analytical applications. It has redox properties that allow it to act as an electron carrier in biological systems. Clinically, methylthioninium is used in the treatment of methemoglobinemia by restoring hemoglobin’s oxygen-carrying capacity. It is also used as an antidote in certain drug- or chemical-induced toxicities. In addition, methylthioninium has antimicrobial and antiseptic properties. It is widely employed as a biological stain in microscopy and laboratory diagnostics. The compound is used in pharmaceutical analysis as a reference standard. It has applications in urinary tract infections as a mild antiseptic. Methylthioninium is also studied for neurological and psychiatric conditions. Its versatility makes it valuable in both clinical and laboratory settings.
