Glyceryl trinitrate
Organic nitrates
Organic nitrates
The classic nitrate: under the tongue it relieves an angina attack in minutes; as an infusion it treats acute coronary syndromes and acute heart failure.
Also called: Nitroglycerin, GTN
Quick facts
- Group
- Organic nitrates
- Target
- Soluble guanylate cyclase (activated by the nitric oxide released from the drug)
- Used for
- Relief of an acute angina attack · Intravenous
- Key effects
- Headache · Flushing · Reflex tachycardia
- Monitor
- Blood pressure and heart rate
- ATC
- C01DA02
No doses: the clinician sets them by the current guideline.
Mechanism of action
Glyceryl trinitrate releases nitric oxide (in part through mitochondrial aldehyde dehydrogenase, ALDH2). Nitric oxide activates soluble guanylate cyclase; cGMP rises, myosin light chains are dephosphorylated and smooth muscle relaxes. Venodilation lowers preload and myocardial oxygen demand; at higher doses arteries and coronary arteries also dilate.
- Glyceryl trinitrate releases nitric oxide in the vessel wall
- Nitric oxide activates guanylate cyclase and cGMP rises
- Veins relax: less preload and less oxygen demand
- Coronary arteries dilate and spasm is relieved
Indications
- Relief of an acute angina attack and prevention just before exertion Stable angina →
- Intravenous: heart failure in acute myocardial infarction, and angina not controlled by sublingual nitrates and beta blockers Myocardial Infarction (Heart Attack) →
- Intravenous: acute heart failure and perioperative hypertension Heart failure →
- Coronary spasm (vasospastic angina) Vasospastic (Prinzmetal) angina →
Adverse effects
Common
- Headache, often throbbing
- Dizziness and lightheadedness on standing
- Flushing
- Reflex tachycardia
Contraindications
- Use of PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) or riociguat
- Severe anaemia
- Raised intracranial pressure (for example cerebral haemorrhage or head injury)
- Acute circulatory failure or shock
- Intravenous form: pericardial tamponade, restrictive cardiomyopathy or constrictive pericarditis
Key interactions
- Sildenafil, tadalafil, vardenafil, avanafil
- Severe hypotension, syncope or myocardial ischaemia; contraindicated
- Riociguat
- Hypotension; contraindicated
- Ergotamine and related drugs
- Higher ergot levels and angina; avoided
- Heparin (with the intravenous form)
- Weaker anticoagulant effect; aPTT is followed closely
- Alcohol and other vasodilators or antihypertensives
- Additive fall in blood pressure
What is monitored
- Blood pressure and heart rate
- Chest pain relief and ECG in acute coronary syndromes
- aPTT if heparin is given with the infusion
Administration and safety
- Sublingual tablets dissolve under the tongue and are not swallowed; the patient sits or lies down first.
- Tablets stay in their original glass bottle, tightly closed, because they lose potency.
- Intravenous glyceryl trinitrate binds to PVC tubing and some in-line filters: non-PVC sets, glass bottles and an infusion pump are used.
Pregnancy and breastfeeding
Animal studies show no harm, but human data are limited; it is used in pregnancy when the benefit justifies it.
Nursing care
- Check blood pressure before each dose and during the infusion; hold and report hypotension.
- Ask about sildenafil, tadalafil or vardenafil use before giving any nitrate.
- Teach that chest pain not relieved by the doses the label allows is an emergency.
- Headache is common at the start and usually fades with continued use; teach not to drink alcohol with it.
Pharmacokinetics
- Absorption
- Rapid through the oral mucosa (sublingual tablet or spray); large first-pass loss if swallowed
- Metabolism
- Liver reductase, red cells and vessel walls, to di- and mononitrates
- Half-life
- A few minutes
- Onset and duration
- About 1 to 3 minutes after a sublingual dose; the effect is short-lived
Test yourself
Think of the answer, then tap the question to see it.
How fast does sublingual glyceryl trinitrate act, and why is it given under the tongue?
Within about 1 to 3 minutes; the oral mucosa absorbs it straight into the blood and avoids the large first-pass loss in the liver.
Why is intravenous glyceryl trinitrate given through non-PVC tubing?
It migrates into PVC plastic, so less drug reaches the patient and the delivered dose becomes unpredictable.
Which two contraindications of glyceryl trinitrate are classic besides PDE5 inhibitors?
Raised intracranial pressure and severe anaemia (also shock and, for the intravenous form, tamponade or constrictive pericarditis).
Why are sublingual tablets kept in their original glass bottle?
Glyceryl trinitrate is volatile and loses potency if exposed or stored in other containers.
Connections
← Back to the class: Organic nitrates
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - NITROGLYCERIN tablet (DailyMed (U.S. National Library of Medicine), 2026); DailyMed - NITROGLYCERIN injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.