Although one group of drugs (including amyl nitrite and glyceryl tinitrate) has been used in the treatment of angina for over 100 years, the mode of action became clear only after the endothelium-derived relaxing factor had been identified as nitric oxide in 1987. Originally sodium nitrite was included in this group of drugs but it rapidly fell out of favour. Recently, however, interest in its therapeutic use has been revived. The medical uses of saltpetre (potassium nitrate) may be due to the presence of nitrite as an impurity.
