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Nitrates are medications that have been used in the treatment of heart conditions for more than 100 years. They are commonly prescribed to prevent and relieve angina – a type of chest pain, pressure or discomfort that is the main symptom of coronary artery disease. Nitrates prevent and relieve angina by addressing its cause: a lack of oxygen-rich blood to the heart (cardiac ischemia).
Nitrates are the most commonly prescribed vasodilators, or medications that widen the blood vessels. They work by converting into nitric oxide inside the body. Nitric oxide relaxes smooth muscles, most notably the muscles  of the heart and blood vessels. As a result, stress on the wall of arteries is reduced, which reduces the heart's need for blood while increasing the flow of blood to the heart. However, depending on the dose, nitrates may not reduce blood pressure because they operate through a different mechanism. At higher doses, however, blood pressure may drop.
Nitrates can be taken in many forms, including:
- Intravenous injections, the fastest strategy for relieving angina.
- Oral sprays or tablets that dissolve under the tongue (sublingual), dissolve on the side of the mouth or are chewable. These are designed to relieve an angina attack as it is happening. In the past, patients may have been advised that all nitrates in these forms will produce a tingling or burning sensation in the mouth indicating that the drug is active. This is no longer true for most nitrates, and the absence of tingling does not mean that the drug is not working. Patients should wait at least five minutes to see if chest pain diminishes before taking a second dose of the medication. No more than a total of three doses at five minutes apart should be taken during a given period of time.
In the past, patients have been advised to take all three doses before contacting emergency medical services if chest pains do not resolve. In 2004, however, the American Heart Association updated its guidelines to recommend contacting emergency help if the chest pain does not resolve within five minutes of the first dose. This recommendation may be changed by individual physicians who are familiar with the particulars of each patient.
- Tablets or time-release capsules. Designed for long-term use in the prevention of angina attacks, tablets or time-release capsules require a longer period of time before taking effect than the strategies listed above.
- Ointments or skin patches. Designed for long–term use to prevent angina attacks.
Nitrates may also be prescribed in the following situations:
- During a heart attack, an event that can result in permanent heart damage or death. It is also known as a myocardial infarction, because part of the heart muscle (myocardium) may die (infarction). A heart attack occurs when one of the coronary arteries becomes severely or totally blocked, usually by a blood clot. The leading cause of coronary artery disease is atherosclerosis, or "hardening of the arteries."
- In the management of heart failure, a serious condition in which the heart is not pumping well enough to meet the body’s demand for oxygen. By opening (dilating) the blood vessels, nitrates reduce the pressure in the veins and make it easier for the heart to pump blood. In this situation, nitrates are usually administered intravenously in a hospital setting.
 After stenting. Stenting is the procedure by which a small, metal mesh tube (stent) is inserted into an artery, often immediately after an angioplasty, to hold it open. Nitrates may reduce the incidence of myocardial necrosis (tissue death within the heart caused by a lack of oxygen) following this procedure.
- In the management of pulmonary hypertension. This condition occurs when the blood pressure in the lungs becomes elevated, often as a result of cardiac disease.
Types of nitrates include:
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amyl nitrate
erythrityl tetranitrate
erythritol tetranitrate
glyceryl tetranitrate
pentaerythritol tetranitrate
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isosorbide mononitrate
mannitol hexanitrate
nitroglycerin
isosorbide dinitrate
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