A patient on nitroprusside therapy developed cyanide toxicity. Sodium nitrite was administered i.v. to combat this poisoning. Beneficial effect of sodium nitrite in this case is dependent on:
Direct chelation of cyanide with sodium nitrite
Vasodilatation caused by sodium nitrite
Conversion of hemoglobin to methemoglobin by sodium nitrite
Facilitation of cyanocobalamin formation by sodium nitrite
Cyanide has very high affinity for the enzymes of respiratory chain paicularly cytochrome oxidase. Methemoglobin possesses even higher affinity for cyanides. It can free the enzymes due to competitive inhibition for cyanide. Nitrates act by reducing hemoglobin to methemoglobin, which removes cyanide from the enzymes.
Hypeension, Arrhythmias, Dyslipidemia