Antidote
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.