Nitroglycerin

An explosion caused by nitroglycerin. Source:National Park Service

Other Names

Nitroglycerin contains several nitrogen and oxygen atoms. Source:Wikimedia Commons

Uses

Nitroglycerin is primarily used to treat and prevent angina associated with reduced blood flow to the heart. It is also used to treat some patients with congestive heart failure and to reduce the work done by the injured heart immediately after a heart attack.

How Nitroglycerin Is Taken

Nitroglycerin is taken whenever patients notice the characteristic discomfort of angina, which is sometimes described as a squeezing or stabbing pain in the upper chest that may radiate to the neck or arm (typically on the left); it can also be taken at the expectation of angina. The drug may be taken by mouth (by dissolving a tablet under the tongue) or given through the skin via a medicated patch. Nitroglycerin is often recommended in combination with beta blockers or calcium channel blockers to further improve blood flow to the heart.

The drug is sold as sublingual tablets, buccal tablets, long-acting capsules, or spray to be used orally. The buccal extended-release tablets and the extended-release tablets and capsules are usually taken three to six times a day. The sublingual tablet and spray are used as needed to relieve chest pain that has already started or to prevent pain before activities known to provoke attacks. The drug can also be given intravenously.^[1]

Recommended dose ranges are as follows:^[2]

• Sublingual NTG tablets 0.3-0.6 mg as needed, maximum 3 doses in 15 min
• Sublingual NTG spray 0.4 mg as needed, maximum 3 doses in 15 min
• NTG paste/ointment ½-2" 2% NTG every 8 hours, with 8-10 h free of NTG every day
• NTG patch 0.1-0.8 mg/h, on 12 h/off 12 h

How It Works

Nitroglycerin works by rapidly degrading in the body to release nitric oxide (NO), a simple molecule that is normally a gas at room temperature and pressure but which dissolves well in the blood. Nitric oxide acts on the cells that line blood vessels (the endothelium) to relax them, thus increasing the diameter of the blood vessels and reducing blood pressure.^[3]

How the body affects Nitroglycerin

Benefits

Side Effects

Side effects from nitroglycerin are common; these include headache, rash, dizziness, upset stomach, or flushing. More serious side effects include blurred vision, dry mouth, chest pain, and fainting.

Risks and Precautions

Interactions

History

A copy of Murrell's 1882 book. Source: Lane Medical Library, Stanford University

Nitroglycerin is not found in nature; it was first synthesized in 1847 by treating glycerin with a mixture of sulfuric acid and nitric acid. The first batches were described by its inventor, Ascanio Sobrero, as yellow and oily, with a sharp sweet taste. Sobrero discovered its explosive properties when a small sample blew up and injured his face and hands. The intrepid chemist's taste test rapidly revealed its profound physiological effects:

A trace of nitroglycerin placed upon the tongue, but not swallowed, gives rise to a most pulsating, violent headache, accompanied by great weakness of the limbs. A dog was given a few centigrams of nitroglycerine. It soon began to foam at the mouth and then vomited. Despite the fact that the greater part of the nitroglycerine had thus been eliminated from the system, within seven or eight minutes the animal had fallen down and almost ceased breathing. A dose of olive oil and ammonia was administered. The animal revived somewhat, and remained for some two hours whining, trembling violently, and beating its head on the wall. A post-mortem examination showed that the vessels of the brain and heart were suffused with blood and much distended.^[4]

Other European physicians attempted to safely exploit nitroglycerin's effects. William Murrell published a book "Nitro-Glycerine in Angina Pectoris" in 1882 that described the physiology, pharmacology, and best practices of the day.^[5]

Before the introduction of therapeutic nitroglycerin, angina was commonly treated by nonspecific remedies such as opium, chloroform, or bleeding. The introduction of nitroglycerin represented a significant advance in cardiology.

Alternatives

The nitrate class of drugs also releases NO into the blood and relaxes the blood vessels; these include isosorbide mononitrate and isosorbide dinitrate. Persons with decreased blood flow to the heart may also benefit from reducing their platelet activty with aspirin, improving their blood lipids with statin drugs, or reducing their blood pressure.

References

1. ↑ Hill NS, Antman EM, Green LH, Alpert JS. Intravenous nitroglycerin. A review of pharmacology, indications, therapeutic effects and complications. Chest. 1981 Jan;79(1):69-76. Citation
2. ↑ Rosendorff C. Essential Cardiology Principles and Practice, 2nd Edition. Humana Press, 2005.
3. ↑ Ignarro LJ. After 130 years, the molecular mechanism of action of nitroglycerin is revealed. Proc Natl Acad Sci U S A. 2002 Jun 11;99(12):7816-7. Citation | Full Text | PDF
4. ↑ Macdonald GW. Historical papers on modern explosives. London, Whittaker & Co., 1912
5. ↑ Murrell WA. Nitro-glycerine as a remedy in angina pectoris. George S. Davis, Medical Publisher, Detroit, 1882. Full Text