Related Information about Methylene Blue

Methylene blue (MB), or methylthioninium chloride, is the primary compound of eosin methylene blue (EMB) agar, a medication and microbiological dye. It is used as an antidote to drug-induced methemoglobinemia and in surgical sciences for staining the surgical field. It was reported to show activity against Plasmodium falciparum strains and to have the potential to be used as an antimalarial agent in combination with other drugs[1].

History

Working in Germany, Heinrich Caro synthesized Methylene blue as a dye in 1876. Soon after, it was studied by Paul Ehrlich, who used it to stain Mycobacterium tuberculosis. Methylene blue also stains Plasmodium malariae and has been tried as an antimalarial agent with an adequate clinical effect. In the late nineteenth century, it was used in cases of psychotic agitation but was later replaced by newly discovered barbiturates[2].

Use

Methylene blue is a tricyclic phenothiazine approved by the FDA and EMA for treating methemoglobinaemia and malaria. It is also used to inactivate viruses in blood products for transfusion in the presence of UV light. It has been used with promising results in the treatment of mood disorders. Outside of neuropsychiatry, methylene blue is used for acute treatment of carbon monoxide or cyanide poisoning, methemoglobinemia, as a urinary antiseptic, in septic shock, for the treatment of malaria, and as an in vivo dye during surgical procedures[3].

Pharmacokinetics

The bioavailability of methylene blue is significantly higher following intravenous administration. Thus, the US Food and Drug Administration warned about the concurrent use of serotonin reuptake inhibitors and intravenous use of methylene blue. Methylene blue is eliminated via the kidneys, with about three quarters in the form of its reduced form, leukomethylene blue, as well as demethylated metabolites, azure A and azure B. Azure B, in particular, has been reported to have antidepressant-like properties in animal models. The terminal half-life of elimination has been estimated at 5–6.5 h.

Side effects

In humans, methylene blue is usually well tolerated. Its main side effects are gastrointestinal tract irritation and urinary tract burning; some patients find urine discoloration troublesome.

References

[1] Deniz Gazel, Alper Akçalı, Müşerref Tatman Otkun. “In vitro activity of methylene blue and eosin methylene blue agar on colistin-resistant A. baumannii: an experimental study.” Journal of medical microbiology (2019).

[2] Alda, Martin. “Methylene Blue in the Treatment of Neuropsychiatric Disorders.” CNS drugs 33 8 (2019): 719–725.

[3] Giulio Scigliano , Giuseppe Augusto Scigliano. “Methylene blue in covid-19.” Medical hypotheses 146 (2021): Article 110455.