Which antidote should be used for cyanide poisoning?

The appropriate antidote for cyanide poisoning is amyl nitrate. Amyl nitrate works by converting hemoglobin to methemoglobin, which then binds to cyanide, forming a stable complex. This process helps to reduce the amount of free cyanide in the bloodstream, allowing for its elimination or reducing its toxic effects on the tissues. Amyl nitrate is particularly effective in situations where cyanide exposure has occurred, such as in cases of smoke inhalation from house fires or certain chemical exposures.

In contrast, other options like glucagon, digoxin Fab, and calcium gluconate are not used for cyanide poisoning. Glucagon is primarily used for hypoglycemia and certain types of cardiac arrhythmias, while digoxin Fab is an antidote for digoxin toxicity. Calcium gluconate is commonly administered for calcium channel blocker overdoses or certain types of hyperkalemia but has no effect on cyanide toxicity. Therefore, amyl nitrate is specifically targeted towards mitigating the harmful effects of cyanide and is the correct antidote in this scenario.