A Rare Case of Drug Induced Methemoglobinemia

Methemoglobin is formed when ferrous ion (fe++) in the heme group is oxdised to ferric (fe+++) state. Methemoglobin is unable to combine with oxygen resulting in decreased oxygen carrying capacity of the blood. Reference range of methemoglobin is 15%, it results in pseudocyanosis. Levels >30% can cause headache and dyspnea and levels >70% can also prove to be fatal. Methemoglobinemia can be inherited or acquired from drugs or chemicals containing nitro or amino group and raised levels can be treated by intravenous methylene blue or red cell transfusion.