Methylene Blue--a therapeutic dye for all seasons?

Since it was first synthesised in 1876, Methylene Blue (MB) has found uses in many different areas of clinical medicine, ranging from dementia to cancer chemotherapy. In addition, MB formed the basis of antimicrobial chemotherapy--particularly in the area of antimalarials--and eventually led to the discovery of the neuroleptic drug families. More recently, the photosensitising potential of MB and its congeners has been recognised, and these are being applied in various antimicrobial fields, especially that of blood disinfection. The range of activities of MB is due to the combination of its simple chemical structure and facility for oxidation-reduction reactions in situ.