Nitrates are medications that come under the umbrella of a larger group called vasodilators, which dilate the walls of blood vessels. Nitrates are primarily used to treat angina pectoris, which is pain caused by reduced blood flow to the heart muscle; as well as hypertension, and heart failure.
More recently, they’ve also been approved for the topical treatment of anal fissures. The most commonly used nitrates include nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate.
Out of these, nitroglycerin has a rapid and short-lasting action, so it is typically given through rapidly absorbable routes like sublingual, oral spray, or intravenously, to treat acute anginal pain or hypertension; or as transdermal patches or topical ointments for long-term prevention. Nitroglycerin can also be administered rectally for the treatment of anal fissures.
On the other hand, isosorbide dinitrate and isosorbide mononitrate have a longer duration of action and are typically administered orally as tablets or sustained-release capsules, which makes them useful for the long-term prevention of angina pectoris, or to treat clients with heart failure.
Once absorbed into the blood, nitrates quickly get converted into their active form, called nitric oxide. Nitric oxide diffuses to the smooth muscle cells of both veins and arteries, causing wall relaxation and vasodilation.