This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
Mechanism of action of sodium nitrite in cyanide poisoning 
Select and explain. 
A. Increased blood flow to liver, B. Produces methemoglobinemia, C. Increased blood flow to kidney, D. Increased blood flow to hea
B: Produces methemoglobinemia
Answer: B: Produces methemoglobinemia 
Explanation: Cyanide poisoning:- Nitrates generate methaemoglobin which has high affinity for cyanide radical and forms cyanomethaemoglobin. However, this may again dissociate to release cyanide. Therefore, sodium thiosulfate is given to form Sod. thiocyanate which is poorly dissociable and is excreted in urine. Cytochrome and other oxidative enzymes are thus protected from cyanide. Ref:- kd tripathi; pg num:-545