Drug-induced methaemoglobinaemia presenting with angina following the use of dapsone.

Anaemia may result in tissue hypoxia which may induce or exacerbate symptoms of ischaemia. Tissue hypoxia may however also result from the presence of haemoglobin with altered oxygen-binding characteristics. Drug-induced methaemoglobinaemia in which oxygen is irreversibly bound to haemoglobin may complicate the use of some common drugs. This condition may result in severe tissue hypoxia, which is rapidly and cheaply reversed by methylene blue.