• Leah K Cambal, Megan R Swanson, Quan Yuan, Andrew C Weitz, Hui-Hua Li, Bruce R Pitt, Linda L Pearce, and Jim Peterson.
• Department of Environmental and Occupational Health, Graduate School of Public Health, The University of Pittsburgh, 100 Technology Drive, Pittsburgh, Pennsylvania 15219, USA.
• Chem. Res. Toxicol. 2011 Jul 18; 24 (7): 1104-12.

AbstractSodium nitrite alone is shown to ameliorate sublethal cyanide toxicity in mice when given from ∼1 h before until 20 min after the toxic dose as demonstrated by the recovery of righting ability. An optimum dose (12 mg/kg) was determined to significantly relieve cyanide toxicity (5.0 mg/kg) when administered to mice intraperitoneally. Nitrite so administered was shown to rapidly produce NO in the bloodsteam as judged by the dose-dependent appearance of EPR signals attributable to nitrosylhemoglobin and methemoglobin. It is argued that antagonism of cyanide inhibition of cytochrome c oxidase by NO is the crucial antidotal activity rather than the methemoglobin-forming action of nitrite. Concomitant addition of sodium thiosulfate to nitrite-treated blood resulted in the detection of sulfidomethemoblobin by EPR spectroscopy. Sulfide is a product of thiosulfate hydrolysis and, like cyanide, is known to be a potent inhibitor of cytochrome c oxidase, the effects of the two inhibitors being essentially additive under standard assay conditions rather than dominated by either one. The findings afford a plausible explanation for an observed detrimental effect in mice associated with the use of the standard nitrite-thiosulfate combination therapy at sublethal levels of cyanide intoxication.© 2011 American Chemical Society

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