Can it cause harm if you take nitro glycerine tabs when you really don't need them?

Taking nitroglycerin when not needed can lead to severe headaches for one. It also could lead to an unsafe drop in blood pressure and can cause tachycardia which is a rapid heart rate, palpitations and fainting. He should probably be tapered down off the medication if he has been on more than a few weeks. Stopping abruptly can lead to spasm of the coronary arteries. Are we talking about a daily dose of nitro or are we speaking of the subligual form to be used as needed during periods of chest pain? If they are the as needed sublingual form, he can keep them until they expire in case he does have an episode of chest pain but if it is a daily dose he should not take them and ask the Dr if he needs to taper off.