Methylene blue

Q: Methylene blue (MB) should be given with caution in patients with 

A) Pulmonary hypertension
B) Glucose-6-phosphate dehydrogenase (G6PD) deficiency
C) Severe liver insufficiency
D) On serotonergic agents
E) All of the above


Answer: E

Use of Methylene blue has seen a surge in recent years in critical patients in a quest to quickly blunt refractory vasoplegia. But it should be given with caution and history and concomitant use of other drugs should be taken into consideration. Most commonly missed is the use of SSRIs by patients who receive  MB. 

In patients with G6PD-deficiency, methylene blue catalyzes the oxidation of ferrous iron in hemoglobin to ferric iron causing paradoxical methemoglobinemia and hemolysis.

#pharmacology
#cardiovascular


References:

Gillman P.K. (October 2006). "Methylene blue implicated in potentially fatal serotonin toxicity". Anaesthesia. 61 (10): 1013–4.

 Sikka P, Bindra VK, Kapoor S, Jain V, Saxena KK. Blue cures blue but be cautious. Journal of Pharmacy & Bioallied Sciences. 2011;3(4):543-545. doi:10.4103/0975-7406.90112.