Angina medication: Questions about nitrates answered

nitrate medication

Nitrates are a tried-and-tested treatment for angina, but it’s important to be informed about their usage and potential side effects. Thembi Nkala talks to our guest expert, Dr Sandy Gupta, consultant cardiologist at Whipps Cross/Barts Health NHS Trusts, London.

What are nitrates?

Nitrates have been the basis for the treatment of angina for decades. Angina is an uncomfortable feeling, tightening or pain in your chest that can spread to your arms, back, jaw, neck or stomach. It is caused by narrowing, blockage or spasms within the coronary arteries, which limits the amount of oxygenated blood reaching part of your heart muscle.

Essentially, nitrates dilate – that is, widen or relax – the arteries and the veins not only in the heart but also elsewhere in the body. By dilating the blood vessels of the heart, nitrates can reduce the stress on the heart by improving blood flow to the heart muscle. This will relieve angina symptoms.

Why have I been given this medication?

Many patients with narrowed or blocked arteries do not necessarily need an operation or stents, and tablets can be as effective in relieving symptoms of angina. Nitrates come in fast-acting and long-acting forms. The fast-acting forms are used to relieve angina or to prevent it from occurring just before activities that may bring it on.

They come as a sublingual (under the tongue) spray or sublingual tablets, which are absorbed into the lining of the mouth. They are taken as and when needed.

Long-acting forms, such as pills and patches, are used to prevent angina from happening and are not ideal for stopping sudden attacks of angina symptoms, so these are taken on a regular daily basis.

Every patient is different, so depending on your needs, your doctor may prescribe one or both forms of nitrates.

What should I do if I experience chest pain?

If you’re known to have coronary heart disease and symptoms occur when you are exerting yourself, you need to stop what you're doing and rest, use your GTN spray once or place a nitrate tablet under the tongue.

If it doesn't get better after 5 minutes, use the spray again or place another tablet under your tongue. If your chest pain doesn't resolve after 5 more minutes you need to call 999 for an ambulance. Do not drive yourself or ask anyone else to drive you. Calling an ambulance means you will get care from the paramedics more quickly, who will also get you to hospital more quickly and safely - the ambulance service will prioritise a call like this as a potential heart attack.

Don't use the spray repeatedly. This will make your blood pressure drop too low and you may faint. 

If pain comes on at rest or wakes you up, or is much more frequent with minimal exertion, this is a sign of unstable angina. You should seek medical attention if this happens to you. Make an appointment to see your GP as soon as you can or call an ambulance if the pain doesn't resolve after a few minutes. Sometimes people need to be admitted to hospital to help stabilise them and for further tests and treatments. 

Nitrates dilate the arteries and the veins not only in the heart but also elsewhere in the body

What can I do if I have an angina attack and don’t have my spray with me?

It is important to always keep the nitrate spray with you and to check when it is getting close to expiry and have it renewed. You can buy GTN medicines from a pharmacy without a prescription if necessary. If you do develop a severe angina attack when you don't have your spray, and it doesn't get better after you have rested for a few minutes, you need to seek urgent medical attention for assessment and treatment. 

Do I need to worry about the expiry date?

Yes - out of date medicines won't work as well. A GTN spray has an expiry date of up to three years, whereas GTN tablets in glass bottles expire eight weeks after opening (if they are packaged differently, follow the instructions on the packet or from your pharmacist). So make sure you check the expiry dates of your medicines. If you use GTN tablets, write the date you opened them to remind you.

Will my nitrates stop working if I take them too often?

One of the problems with regular use of nitrates has been the issue of tolerance, which is when the effect of the drug appears to lessen over time. One of the ways to prevent tolerance is to change the dosing of regular nitrate therapy to guarantee a nitrate-free interval.

For example, if patients take nitrate patches, the recommendation is only to wear them for 12 hours to allow a nitrate-free interval of 8–12 hours. This minimises the risk of tolerance. With sublingual (fast-acting) nitrates, make sure you follow your doctor’s instructions on how often you use them within a set time period. Any changes to the dosage or times will need to be discussed with your GP. And if you feel your medication is not effective anymore, inform your doctor.

What are the possible side effects?

The most common side effects of nitrates include headaches, dizziness or light-headedness, flushing or a warm feeling in the face. Not everyone experiences these. If side effects are a problem for you, discuss it with your doctor before you stop taking your nitrates.

Should people use their spray before exercise?

Yes, I often recommend that patients who are stable but do get symptoms of angina with exertion take one to two puffs before a particular activity or take the GTN tablets under the tongue – that is, before angina has occurred. This often allows patients to undertake some degree of physical activity. The effect can last up to 30 minutes.

  • Watch our animation all about angina.
  • Get answers to more common questions about angina.

Fast facts

  • Sit/lie down before taking your fast-acting form of nitrates, because they can lower your blood pressure, which can result in dizziness or fainting.
  • Report any change in symptoms to your doctor, whether the frequency, pattern or severity.
  • If your angina persists even after using your nitrates according to your doctor’s instructions, seek urgent medical help.
  • Nitrates should not be used with erectile dysfunction drugs such as sildenafil (Viagra). Read more about this.
  • Nitrates have been used to treat chest pain since 1870.
  • Nitrates work by dilating the blood vessels.

More useful information