Methylene Blue

Hazard

Toxic by ingestion.

Biological Activity

Biological stain and redox indicator. Inhibits tau filament formation (IC 50 = 1.9 μ M). Also inhibits soluble guanylyl cyclase.

Biochem/physiol Actions

Methylene blue (MB) is a highly recognized histological dye. It plays a vital role in microbiology and pharmacology. It has been employed in staining living organisms and in methemoglobinemia treatment. MB exhibits maximum absorption at 664nm. Exposure to methylene blue leads to various health hazards such as increased heart rate, vomiting, shock, Heinz body formation, cyanosis, jaundice, quadriplegia and tissue necrosis in humans

Safety Profile

Poison by ingestion,intraperitoneal, intravenous, and subcutaneous routes.Human systemic effects: cyanosis, blood changes.Experimental reproductive effects. Mutation datareported. When heated to decomposition it emits verytoxic fumes of NOx, SOx, and

Veterinary Drugs and Treatments

Methylene blue is used primarily for treating methemoglobinemia secondary to oxidative agents (nitrates, chlorates) in ruminants. It is also employed occasionally as adjunctive or alternative therapy for cyanide toxicity. Intra-operative methylene blue is also being used to preferentially stain islet-cell tumors of the pancreas in dogs in order to aid in their surgical removal or in determining the animal’s prognosis.

Purification Methods

Crystallise the chloride from 0.1M 664 2HCl (16mL/g), the crystals are separated by centrifugation, washed with chilled EtOH and diethyl ether, and dried under vacuum. Crystallise it from 50% aqueous EtOH, wash it with absolute EtOH, and dry it at 50-55o for 24hours. It has also been crystallised from *benzene/MeOH (3:1). It has been salted out with NaCl from a commercial concentrated aqueous solution, then crystallised from water, and dried at 100o in an oven for 8-10hours. [Beilstein 27 III/IV 5152.]

Definition

ChEBI: An organic chloride salt having 3,7-bis(dimethylamino)phenothiazin-5-ium as the counterion. A commonly used dye that also exhibits antioxidant, antimalarial, antidepressant and cardioprotective properties.

General Description

Methylene blue, also known as methylthioninium chloride, is a photoactive phenothiazine dye. It is a small molecular weight dye, which is effective against Gram positive and Gram negative bacteria.