Medical Use
Nitroglycerin was first used by William Murrell to treat anginal attacks in 1878, with the discovery published in 1878.
Nitroglycerin belongs to a group of drugs called nitrates, which includes many other nitrates like isosorbide dinitrate (Isordil) and isosorbide mononitrate (Imdur, Ismo, Monoket). These agents all exert their effect by being converted to nitric oxide in the body by mitochondrial aldehyde dehydrogenase, and nitric oxide is a potent natural vasodilator.
In medicine, where it is generally called glyceryl trinitrate, nitroglycerin is used as a heart medication. It is used as a medicine for angina pectoris (ischemic heart disease) in tablets, ointment, solution for intravenous use, transdermal patches, or sprays administered sublingually. Patients who experience angina when doing certain physical activities can often prevent symptoms by taking nitroglycerin 5 to 10 minutes before the activity. Some forms of nitroglycerin last much longer in the body than others. These may come in the form of a pill taken one, two, or three times per day, or even as a patch. It has been shown that round-the-clock exposure to nitrates can cause the body to stop responding normally to this medicine. Experts recommend that the patches be removed at night, allowing the body a few hours to restore its responsiveness to nitrates. Shorter-acting preparations can be used several times a day with less risk of the body getting used to this drug.
Angina pectoris is due to an inadequate flow of blood and oxygen to the heart. It is believed that nitroglycerin corrects the imbalance between the flow of oxygen and blood to the heart. The principal action of nitroglycerin is vasodilation—widening of the blood vessels. At low doses, nitroglycerin will dilate veins more than arteries, but at higher doses it also dilates arteries and is a potent antihypertensive agent. In cardiac treatment the lowering of pressure in the arteries reduces the pressure against which the heart must pump, thereby decreasing afterload. Dilating the veins decreases cardiac preload and leads to the following therapeutic effects during episodes of angina pectoris: subsiding of chest pain, decrease of blood pressure, increase of heart rate, and orthostatic hypotension.
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