Often, the first thing that medical professionals will do for cyanide poisoning is to give amyl nitrate or sodium nitrate. These work by making the cyanide attach (stick) to a chemical called methemoglobulin. When it is stuck to methemoglobulin, cyanide is not as dangerous. However, methemoglobulin will only stick to cyanide for a while. Eventually, it will not stick any more. This is why another medicine is needed.