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How should I use glyceryl trinitrate (GTN) spray or tablets for angina chest pain? 

Posted
Updated
ByMy Patient Advice
Author: Harry Whitmore, Medical Student | Reviewed by: Dr. Rebecca Fernandez, MBBS

Glyceryl Trinitrate (GTN) is the â€˜fire extinguisher’ for angina. It is a rapid-acting vasodilator, meaning it widens your blood vessels within seconds to improve blood flow to the heart. Whether you carry the spray or the tiny tablets, knowing exactly how to use them, and knowing the strict timeline for when to call for help, is the most important part of your angina safety plan. 

What We’ll Discuss in This Article 

  • Why you must sit down before using GTN. 
  • Step-by-step instructions for using the spray correctly. 
  • How to handle the small tablets if you don’t use the spray. 
  • The critical ‘5-Minute Rule’ for calling 999. 
  • Using GTN to prevent pain before exercise (prophylaxis). 
  • Common side effects like ‘head rushes’ and headaches. 
  • Storage tips: why tablets spoil faster than sprays. 

Step 1: Preparation (The Golden Rule) 

Before you even reach for your spray, you must stop what you are doing and sit down. 

GTN works by lowering your blood pressure rapidly. If you use it while standing up, gravity can pull blood away from your brain, causing you to faint. Fainting during a heart episode is dangerous. Find a chair, a wall, or even sit on the floor if necessary. 

Step 2: How to use the GTN Spray 

Most patients are prescribed the spray because it has a longer shelf life. It is designed to be absorbed through the lining of your mouth, not your stomach. 

  1. Prime it: If you haven’t used the bottle for a week or more, spray it into the air once to check it works. 
  1. Aim: Hold the bottle upright close to your mouth. 
  1. Spray: Open your mouth and lift your tongue. Spray one dose under your tongue. 
  1. Close: Close your mouth immediately. 
  1. Do Not Inhale: Do not breathe in the spray like an asthma inhaler. You want the liquid to settle under your tongue, not go into your lungs. 

Step 3: How to use GTN Tablets 

If you prefer tablets, the principle is the same: absorption through the mouth lining. 

  1. Place: Put one tablet under your tongue. 
  1. Dissolve: Let it dissolve naturally. Do not swallow it and do not chew it. If you swallow it, stomach acid will destroy the medicine before it can work. 
  1. Spit (Optional): If the pain goes away quickly and the tablet is still there, you can spit the remainder out to reduce the risk of a headache. 

The Emergency Protocol: When to Call 999 

Knowing when to stop treating yourself and start calling for help is vital. Follow this strict NHS timeline: 

  1. Dose 1: Sit down and take the first dose. Wait 5 minutes. 
  1. Dose 2: If the pain is still there (even if it’s milder), take a second dose. Wait 5 minutes. 
  1. Call 999: If the pain is still there 5 minutes after the second dose, call 999 immediately. Do not take a third dose and wait again; treat this as a potential heart attack. 

Can I use GTN to prevent pain? 

Yes. This is called â€˜prophylactic use.’ If you know a specific trigger always causes you pain, like walking up a steep hill or going out in freezing weather, you can take a dose of GTN 2 to 3 minutes before you start the activity. 

This widens the arteries in advance, often allowing you to complete the task without any pain at all. 

Managing Side Effects 

GTN is a powerful drug, and its effects can feel intense. 

  • The â€˜Head Rush’: You may feel flushed, hot, or dizzy immediately after taking it. This is why sitting down is so important. 
  • The â€˜GTN Headache’: Widening blood vessels in the head often causes a sharp, throbbing headache. This is normal and usually passes quickly. Do not be afraid of the headache, treating your heart is the priority. 

Storage and Expiry 

  • Sprays: usually last 2–3 years. Check the date on the bottom. 
  • Tablets: These are very unstable. Once you open the bottle, they expire after just 8 weeks.9 You must write the date you opened the bottle on the label and discard it 8 weeks later, even if plenty of pills are left. 

Conclusion 

Your GTN spray is your lifeline. It should be with you at all times, not in a bathroom cabinet or a car glovebox. Used correctly, it allows you to manage stable angina confidently. Remember the golden rules: always sit down, spray under the tongue, and if two doses don’t work after 15 minutes total, dial 999. 

Would you like me to explain the difference between GTN spray and â€˜preventative’ daily tablets like Isosorbide Mononitrate? 

Can I overdose on GTN spray? 

Taking too much can cause a severe drop in blood pressure (hypotension), leading to fainting, cold sweat, and a fast heart rate. Stick to the prescribed dose (usually 1 or 2 sprays). 

Does GTN expire? 

Yes, and using expired GTN is dangerous because it may not work when you need it most. Tablets expire very quickly (8 weeks after opening); sprays last much longer. 

Why does it taste like burning? 

A slight burning or tingling sensation under the tongue is normal and actually indicates the medication is fresh and working. If the tablets don’t tingle, they might be expired. 

Can I drink alcohol with GTN? 

You should be very careful. Alcohol is also a vasodilator. Combining alcohol and GTN can cause your blood pressure to drop dangerously low, causing you to collapse. 

What if I swallow the spray by accident? 

It won’t harm you, but it won’t work for your chest pain. The liver breaks it down before it reaches the heart. You may need to take another dose properly (under the tongue) if the pain persists.  

Can I drive after using it? 

No. You should not drive while having chest pain, and the medication itself can cause dizziness. Wait until you are fully recovered and pain-free before driving. 

Can I take Viagra (Sildenafil) if I use GTN? 

Absolutely not. This is a fatal combination. Both drugs drop blood pressure. Taking them together can cause a catastrophic, life-threatening collapse. You must tell your doctor if you use erectile dysfunction medication. 

Authority Snapshot 

This article was written by Dr. Rebecca Fernandez, a UK-trained physician (MBBS) with extensive experience in emergency medicine and cardiology. Dr. Fernandez has educated countless patients on the correct use of ‘rescue’ medication, ensuring they understand not just how to use it, but why following the safety steps is vital to prevent falls and complications. This content has been reviewed to ensure strict alignment with NHS and BHF safety guidelines. 

Harry Whitmore, Medical Student
Author
Dr. Rebecca Fernandez, MBBS
Reviewer

Dr. Rebecca Fernandez is a UK-trained physician with an MBBS and experience in general surgery, cardiology, internal medicine, gynecology, intensive care, and emergency medicine. She has managed critically ill patients, stabilised acute trauma cases, and provided comprehensive inpatient and outpatient care. In psychiatry, Dr. Fernandez has worked with psychotic, mood, anxiety, and substance use disorders, applying evidence-based approaches such as CBT, ACT, and mindfulness-based therapies. Her skills span patient assessment, treatment planning, and the integration of digital health solutions to support mental well-being.

All qualifications and professional experience stated above are authentic and verified by our editorial team. However, pseudonym and image likeness are used to protect the reviewer's privacy. 

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