A compound found in the blood following ingestion of nitrates, aspirin substitutes, and food preservatives.
A substance formed when the iron atoms of the blood pigment hemoglobin have been oxidized from the ferrous to the ferric form (compare oxyhemoglobin). Methemoglobin cannot bind molecular oxygen and therefore cannot transport oxygen around the body. The presence of methemoglobin in the blood (methemoglobinemia) may result from ingestion of oxidizing drugs or from an inherited abnormality of the hemoglobin molecule. Symptoms are fatigue, headache, dizziness, and cyanosis.
A form of hemoglobin in which the ferrous iron has been oxidized to ferric iron. Methemoglobin cannot transport oxygen. The presence of metHb in the blood may be due to toxic substances such as aniline dyes, potassium chlorate, or nitrate-contaminated water and to atypical responses to benzocaine-like analgesics, among other causes. Methemoglobin also is present in patients with a hereditary deficiency of methemoglobin reductase.
An abnormal variation of hemoglobin, appearing as a chocolate-brown hue, is detected in the blood following exposure to chemicals such as potassium chlorate, nitrates, nitrobenzene, acetanilide, and phenacetin. Given that phenacetin and some of these chemicals are present in common over-the-counter headache and pain relief medications, the risks associated with using such remedies without medical guidance are readily apparent.