GTN - Glyceryl Trinitrate

Nitroglycerin, also known as glyceryl trinitrate (GTN), is a medication in the nitrate family used for heart failure, high blood pressure, anal fissures, painful periods, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine. This includes chest pain from a heart attack. It is taken by mouth, under the tongue, applied to the skin, or by injection into a vein.

Nitroglycerin was written about as early as 1846 and came into medical use in 1878. It is on the World Health Organization's List of Essential Medicines. The drug nitroglycerin (GTN) is a dilute form of the same chemical used as the explosive, nitroglycerin. Dilution makes it non-explosive.

GTN is a prodrug which must be denitrated, with the nitrite anion or a related species further reduced to produce the active metabolite nitric oxide (NO). Organic nitrates that undergo these two steps within the body are called nitrovasodilators, and the denitration and reduction occur via a variety of mechanisms. While the mechanism of action in angina is not entirely clear, it is believed to function by dilating blood vessels.

It was known almost from the time of the first synthesis of GTN by Ascanio Sobrero in 1846 that handling and tasting of nitroglycerin could cause sudden intense headaches, which suggested a vasodilation effect (as suggested by Sobrero). Constantine Hering developed a form of nitroglycerin in 1847 and advocated for its dosing as a treatment of a number of diseases; however, its use as a specific treatment for blood pressure and chest pain was not among these. This is primarily due to his deep rooted focus in homeopathy.

Following Thomas Brunton's discovery that amyl nitrite could be used to treat chest pain, William Murrell experimented with the use of nitroglycerin to alleviate angina pectoris and reduce blood pressure, and showed that the accompanying headaches occurred as a result of overdose. Murrell began treating patients with small doses of GTN in 1878, and the substance was widely adopted after he published his results in The Lancet in 1879.

The medical establishment used the name "glyceryl trinitrate" or "trinitrin" to avoid alarming patients, because of a general awareness that nitroglycerin was explosive.

Glyceryl trinitrate can cause severe hypotension, reflex tachycardia, and severe headaches that necessitate analgesic intervention for pain relief, the painful nature of which can have a marked negative effect on patient compliance. It is contraindicated in conjuction with medications within the sildenafil (PDE5 inhibitor) vasodilator drug family used for erectile dysfunction, such as sildenafil, tadalafil, and vardenafil. 

In 2017, it was the 143rd most commonly prescribed medication in the United States, with more than four million prescriptions.

It is unclear if use in pregnancy is safe for the baby. Overdoses may generate methemoglobinemia.