[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Organic nitrates](https://durgical.com/en/pharmacology/classes/organic-nitrates/) › Glyceryl trinitrate

# 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.

Updated Nov 1, 2026

Also called: Nitroglycerin, GTN

## Quick facts

**Group**
[Organic nitrates](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## 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 →](https://durgical.com/en/conditions/stable-angina/)
- Intravenous: heart failure in acute myocardial infarction, and angina not controlled by sublingual nitrates and beta blockers [Myocardial Infarction (Heart Attack) →](https://durgical.com/en/conditions/myocardial-infarction/)
- Intravenous: acute heart failure and perioperative hypertension [Heart failure →](https://durgical.com/en/conditions/heart-failure/)
- Coronary spasm (vasospastic angina) [Vasospastic (Prinzmetal) angina →](https://durgical.com/en/conditions/vasospastic-angina/)

## Adverse effects

### Common

- Headache, often throbbing
- Dizziness and lightheadedness on standing
- Flushing
- Reflex tachycardia

### Serious (rare, important)

- Severe hypotension and syncope
- Methaemoglobinaemia with high exposure
- Rebound angina if a long nitrate course is stopped abruptly

## 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

## Memory aid

Nitro under the tongue, seated and sure; but if a PDE5 inhibitor came first, nitro is no cure.

## 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.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/glyceryl-trinitrate/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 4

- [Isosorbide dinitrate](https://durgical.com/en/pharmacology/isosorbide-dinitrate/)
- [Isosorbide mononitrate](https://durgical.com/en/pharmacology/isosorbide-mononitrate/)
- [Heparin](https://durgical.com/en/pharmacology/heparin/)
- [Methylthioninium chloride (methylene blue)](https://durgical.com/en/pharmacology/methylthioninium-chloride/)

## Related conditions 4

- [Stable angina](https://durgical.com/en/conditions/stable-angina/)
- [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/)
- [Heart failure](https://durgical.com/en/conditions/heart-failure/)
- [Vasospastic (Prinzmetal) angina](https://durgical.com/en/conditions/vasospastic-angina/)

[← Back to the class: Organic nitrates](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e4642ae0-6a42-4a49-b6d9-d292a0294c77) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - NITROGLYCERIN injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b8af0974-33ea-4dd5-9ff7-3b61272aeb25) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C01DA02) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/glyceryl-trinitrate/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/glyceryl-trinitrate/