Nitroglycerin, also known as glyceryl trinitrate (GTN), is a vasodilator used for heart failure, high blood pressure (hypertension), 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.

Continuous administration and absorption (such as provided by daily pills and especially skin patches) accelerate onset of tolerance and limit the usefulness of the agent.

[citation needed]It may also be given as a sublingual or buccal dose in the form of a tablet placed under the tongue or a spray into the mouth for the treatment of an angina attack.

[14] Tentative evidence indicates efficacy of glyceryl trinitrate in the treatment of various tendinopathies, both in pain management and acceleration of soft tissue repair.

Studies have shown[citation needed] that nitrate tolerance is associated with vascular abnormalities which have the potential to worsen patients' prognosis.

[27][non-primary source needed] Glyceryl trinitrate 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.

Among other roles, cGMP serves as a substrate for a cGMP-dependent protein kinase that activates myosin light chain phosphatase.

Murrell began treating patients with small doses of glyceryl trinitrate in 1878, and the substance was widely adopted after he published his results in The Lancet in 1879.

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