Knowledge Check 2

“I’ve given 3 doses and Methylene Blue isn’t working….” What should you be considering?

• Could there be an underlying NADPH-methaemoglobin-reductase or G6PD deficiency?
• Could there be an underlying HbM haemoglobinopathy?
• Is this a case of Sulfhaemoglobinaemia?
• Have I given too much Methylene Blue? At higher doses Methylene Blue has an oxidation effect.
• Have they taken too much toxin? Does the toxin exposure exceed the power of Methylene Blue, or is there a “double dipping” effect at work (e.g. Dapsone commonly causes a second rise in MetHb after several hours)