Glyceryl trinitrate


Glyceryl trinitrate is the active ingredient of Angised tablets (Nappi code : 703605-003).

General information
Glyceryl trinitrate is a nitrate vasodilator. Nitrate vasodilators are drugs that widen and relax blood vessels to reduce the workload on the heart, and thereby also improve the supply of oxygen-rich blood to the heart.

In South Africa glyceryl trinitrate is registered for the prevention or treatment of acute angina, a suffocating chest pain, which results when partially clogged arteries restrict the flow of oxygen-rich blood to the heart; and chronic heart failure, a condition where the heart can no longer pump enough blood to the body.

If you develop chest pain during exercise, taking these tablets before exercise will increase the amount of exercise you can do before chest pain begins.

Glyceryl trinitrate does not cure any of these conditions, but merely keeps its symptoms under control. For this drug to be effective, it has to be taken regularly.

The first few doses of this drug may cause dizziness if you get up suddenly from sitting or lying down. It is advised to get up carefully, until you know how this drug affects you.

Treatment should not be stopped abruptly, especially if you have been taking this drug for a prolonged period of time. To prevent the return of symptoms, you should decrease your dose gradually only as directed by your doctor.

How does glyceryl trinitrate work?
Vasodilators relax smooth muscle within blood vessels via a direct effect it has on these arterial muscles. As a result it widens and relaxes blood vessels to reduce the workload on the heart, and to increase the supply of oxygen-rich blood to the heart. This leads to chest pain subsiding.

Fast facts

Drug schedule: schedule 3
Available as: glyceryl trinitrate is available as tablets.
What does it do? Glyceryl trinitrate widens blood vessels to reduce chest pain.
Overdose risk: medium
Dependence risk: low
Is glyceryl trinitrate available as a generic? no
Is glyceryl trinitrate available on prescription only? yes

User information

Onset of effect: when tablets are chewed or dissolved in the mouth, it takes effect within minutes.
Duration of action: the tablets have a short action and their effect may last up to 2 hours.
Dietary advice: take tablets with water 1 hour prior to a meal, or 2 hours after a meal.
Stopping this medicine: the decision to stop using this drug should only be made after consulting your doctor.
Prolonged use: some patients may develop a tolerance to the effect of glyceryl trinitrate, which causes its effects to be reduced over time. Speak to your doctor if you suspect your treatment to be losing it efficacy.

Special precautions
Consult your doctor before using this drug if:

  • you have anaemia
  • you have glaucoma
  • you have history of a head injury
  • you have history of heart attack
  • you have low blood pressure
  • you have an under-active thyroid
  • you are taking any other medication

Pregnancy: avoid. It is unknown how this product may affect your baby. Consult your doctor before use, or if you are planning to fall pregnant.
Breastfeeding: avoid. It is unknown how this medication may affect your baby. Consult your doctor before use.
Porphyria: this medication is safe for use.
Infants and children: this medication is not intended for use in children.
The elderly: no special precautions need to be taken.
Driving and hazardous work: caution is advised as use of this medication may lead to dizziness, light-headedness and/or sedation. Avoid such activities until you know how this medication affects you.
Alcohol: avoid concomitant use of alcohol with this medication.

Possible side effects

Side Effect
Consult your doctor

Only if severe
In all cases








heart rhythm disturbances


nausea and vomiting


skin rash


eye pain




Drug interactions

alcoholreduced blood pressure - risk of dizziness and fainting
medication for high blood pressurereduced blood pressure - risk of dizziness and fainting
aspirinrisk of increased GTN side effects
heparinblood-clotting effect of heparin is reduced
sildenafilcauses life-threatening lowering of blood pressure and should be avoided at all times when taking nitrates
sumatriptanpossible vasospasm of coronary arteries which may worsen angina

Overdose action
A small overdose is no cause for concern. In case of intentional large overdose, seek emergency medical attention.

Recommended dosage
Adults, sublingual: one tablet at the onset of an attack repeated up to three times within 15 minutes. If pain persists after taking 3 tablets, call your doctor immediately.

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.

We live in a world where facts and fiction get blurred
In times of uncertainty you need journalism you can trust. For 14 free days, you can have access to a world of in-depth analyses, investigative journalism, top opinions and a range of features. Journalism strengthens democracy. Invest in the future today. Thereafter you will be billed R75 per month. You can cancel anytime and if you cancel within 14 days you won't be billed. 
Subscribe to News24
Voting Booth
Have you entered our Health of the Nation survey?
Please select an option Oops! Something went wrong, please try again later.
28% - 9936 votes
72% - 25948 votes