What is the mechanism by which patients on serotonergic agents are theoretically at an increased risk of developing serotonin toxicity with the administration of methylene blue?
Serotonin is degraded by monoamine oxidase A (MAO-A) enzyme. Methylene blue has been shown in an in vitro study to competitively bind to MAO-A thus serving as a monoamine oxidase inhibitor. For this reason, there is a boxed warning of the potential for serotonin toxicity when methylene blue is administered in patients on serotonergic agents or monoamine oxidase inhibitors.
Ramsay B, et al. Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A (MAO A) confirms a theoretical prediction. Br J Pharmacol. 2007;152:946–951. [PubMed: 17721552]
Contributed by: Oyeyimika Oyekanmi, DO