Treatment in mild cases can be limited to decontamination and observation and oxygen supplementation. In severe cases, treatment includes several antidotes, which are available in a prepackaged cyanide antidote kit [121] . Sodium thiosulfate promotes the formation of thiocyanate by the enzyme rhodanese and leads to excretion of thiocyanate in urine. Sodium nitrate and amyl nitrate lead to formation of methemoglobin, which has an affinity for cyanide, and thus helps to reduce its active presence. The desired methemoglobin level is between 20 and 30% of total hemoglobin [122] . Sodium nitrate is given intravenously, and amyl nitrate vapor can be administered by inhalation through saturated gauze or by emptying an ampule in a respirator reservoir.