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Glyceryl trinitrate is a nitrate that is used to treat angina. It is also referred to as nitroglycerin or GTN. There are numerous preparations available, in oral, transdermal and injectable forms. It is known by different trade names in different countries, according to the manufacturer. Glyceryl trinitrate is available by prescription only in most countries.
Angina causes chest pain due to a lack of blood and oxygen to the heart muscles. Glyceryl trinitrate works by converting to nitric oxide, a naturally occurring chemical in the body that dilates blood vessels. This allows the blood to flow more easily, the transport of oxygen to increase, and the strain on the heart to decrease.
When used for angina, glyceryl trinitrate is best taken before the onset of an attack, or when the first signs are experienced. People with angina often know what may bring on an attack, such as exercise or cold, and can take their nitrate prophylactically. It is well absorbed when placed under the tongue or on the skin, allowing for a quick onset of action.
Tolerance to glyceryl trinitrate may develop quickly, so the patch should not be left on for an extended period. Patients should ensure that they experience a drug-free period each day. This should prevent the drug from not working or the patient needing increasing doses to achieve the same effect. Prescribed dosages should not be exceeded, and drug-free periods recommended by the medical practitioner should be adhered to.
As with any medication, glyceryl trinitrate may interact with other medications or be contraindicated in some disease states. These should be discussed with the prescribing doctor before initiation of treatment. A number of medications are completely contraindicated with nitrates, including some drugs used for erectile dysfunction, such as sildenafil, vardenafil and tadalafil. Some drugs may have additive side effects.
Glyceryl trinitrate may cause adverse effects. Flushing, dizziness and headache may occur, which should resolve fairly quickly. Postural hypotension or dizziness on standing has been reported, especially in patients on concomitant medicines that lower blood pressure, such as anti-hypertensives. It is advisable to avoid driving or operating heavy machinery while taking the drug.
Pregnancy, desired pregnancy and lactation should also be discussed with the prescribing doctor. If adverse effects become severe, medical intervention should be sought. Physicians should also be made aware if symptoms of angina do not improve after administration of the prescribed dose.