The ingestion of a toxic dose of sodium nitrite can produce symptoms such as lethargy, confusion, intoxication, nausea and vomiting. In large doses, nitrite and the production of nitric oxide act as a vasodilator, due to their relaxing action on vascular smooth muscle. The vasodilator action causes a drop in blood pressure (and a possible hypotensive headache).
(Note: Some reports have mistakenly attributed a peaceful nitrite death to the vasodilation and drop in blood pressure associated with the production of nitric oxide (NO): rather than the cerebral hypoxia that results form the high levels of methemoglobin in the blood. )
The altered oxygen-carrying ability of the blood cannot be corrected by the administration of oxygen. Indeed, the measurement of oxygen saturation levels will give a misleadingly high reading. A person suffering from nitrite hypemic hypoxia will show little improvement with the provision of even 100% oxygen.
There is, however, an antidote for sodium nitrite ingestion. The antidote is methylene blue which is administered intravenously. Methylene blue is a thiazide dye that converts methemoglobin back to the desired hemoglobin. With the increase in the use of nitrite as an effective end of life drug, many first responders now routinely carry methylene blue with them (for when they come across incidences of suicide and in order to resuscitate).