Fatal methemoglobinemia caused by inadvertent contamination of a laxative solution with sodium nitrite.

We describe two cases of fatal methemoglobinemia resulting from ingestion of laxative solution inadvertently contaminated with sodium nitrite. Postmortem toxicological examination revealed methemoglobin levels in excess of 75% in both patients--a level that is uniformly fatal. The laxative solution was found to contain sodium nitrite instead of sodium sulphate at a concentration of 15 g/l. The pathophysiology of methemoglobinemia and a review of other reported cases of toxic methemoglobinemia are presented. Marked cyanosis in the face of intact cardiorespiratory function should alert the physician to the possibility of toxic methemoglobinemia.