Nitroglycerin heart drug. Computer model of a molecule of the heart drug nitroglycerin. This drug is used to treat angina pectoris, pain due to the constriction of coronary arteries. It works by relaxing the artery walls and allowing the arteries to expand. The drug is prescribed as a patch, an ointment, pills or as an oral spray. Nitroglycerin is also a very unstable liquid explosive that is used in dynamite. It is prepared by nitrating glycerin. The molecule's chemical formula is C3.H5.N3.O9. The atoms are represented as colour-coded spheres in this ball-and-stick model: carbon (light blue), hydrogen (gold), nitrogen (dark blue) and oxygen (red).