Table 1.

Summary of available cyanide antidotes in the USA with mechanism of action and adverse effects

Antidote	Mechanism	Adverse events/complications
Hydroxocobalamin	Binds cyanide to form cyanocobalamin (vit. B12), which is excreted renally	Hypertension [49], chromaturia [50–53], and acneiform rash. Interference with photometry-based laboratory tests (carboxyhemoglobin, methemoglobin, oxyhemoglobin) [54–56], aspartate aminotransferase, total bilirubin, creatinine, magnesium, and iron [57]. Blood leak alarm during dialysis [44, 58, 59]. Falsely elevated cyanide levels [60]. Allergic reactions [61–63]
Sodium nitrite	Induces methemoglobinemia. Cyanide binds ferric iron, forms cyanomethemoglobin [64]	Methemoglobinemia impairs tissue oxygenation [64–66, 22]. Hypotension, syncope, arrhythmias, seizures, acidosis, methemoglobin formation, and coma/death [67]
Sodium thiosulfate	Acts as a sulfur donor to cyanide to form thiocyanate, relatively non-toxic, renally excreted [68]	Hypotension, prolonged bleeding time, and persistent vomiting [67]