An angina is a condition in which the heart muscle does not get as much blood and oxygen as it needs. This is partly because the arteries of the heart are narrowed either caused by genetic inheritances, age, and poor diet. Nitrates are drugs that help the blood vessels of the heart relax. If the patient is complaining of a headache, the probable cause would be a slight dehydration and the patient must consume more fluids to help the drug become more soluble within the body.