Methylene blue: a treatment for severe methaemoglobinaemia secondary to misuse of amyl nitrite

Poisoning with inhalational nitrites is a recognised cause of methaemoglobinaemia presenting to the emergency department. Methaemoglobin (MetHb) is the oxidised form of haemoglobin and incapable of carrying oxygen. The concentration of MetHb does not exceed 1%-2% in the normal physiological state. Previously reported cases include patients with severe poisoning who were comatosed on presentation or required repeat treatment with methylene blue (MB). Two cases of severe methaemoglobinaemia secondary to misuse of amyl nitrite are presented. A MetHb level of greater than 50% was measured in each case, however, both patients were conscious and talking on presentation and showed clinical and biochemical response to treatment with one dose of MB.