Instability of nitroglycerin tablets

Nitroglycerin is a volatile substance which evaporates from tablets if strict precautions are not taken. The tablets kept in small, amber, tightly capped glass bottles in a refrigerator maintain their potency for three to five months if bottles are opened once a week. After five months the unused tablets should be discarded. Tablets kept in a pill box and carried with the patient will deteriorate in a week and should be discarded thereafter. Cotton, plastic or paper stuffed in the bottle and frequent opening will reduce the potency of NG tablets considerably. Physicians, pharmacists and drug manufacturers should supply full instructions to patients on how to prevent rapid deterioration of their supply.