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Nitroglycerin: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Mar 24, 2020.

1. How it works

  • Nitroglycerin relaxes smooth muscle within the walls of blood vessels (particularly veins) which dilates (widens) them. This helps to relieve chest pain that is caused by a narrowing of the blood vessels, and also reduces how hard the heart has to work to pump blood around the body, reducing blood pressure.
  • Nitroglycerin belongs to a group of medicines called nitrates.

2. Upsides

  • Nitroglycerin sublingual spray or tablets may be used to relieve symptoms of angina (chest pain) in suitable people.
  • Nitroglycerin injection may be given by a doctor's office or before surgery to treat or lower high blood pressure, to control heart failure associated with a heart attack, or to treat angina in suitable patients.
  • Nitroglycerin rectal ointment may be used to treat anal fissure pain.
  • Available as a buccal tablet, a sublingual spray or tablet, a transdermal ointment or film, a rectal ointment, a sublingual powder, an intravenous solution, and an oral capsule.
  • Generic nitroglycerin is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Dizziness, light-headedness, headache, and low blood pressure may occur. This may affect a person's ability to drive or operate machinery. Alcohol, hot weather, and exercise may worsen these effects and result in fainting. Blurred vision may also occur.
  • Rarely, allergic reactions, flushing, severe dizziness, a headache, or persistent nausea or vomiting may occur. Seek urgent medical help.
  • Alcohol toxicity has been reported when high-dose nitroglycerin injection has been given in conjunction with alcohol, or when certain medications (such as disulfiram, cephalosporin antibiotics) are taken at the same time as nitroglycerin and alcohol. Do not drink alcohol while using nitroglycerin.
  • Tolerance can develop to nitroglycerin's effect (tolerance is when the same dose no longer produces the same effect). To prevent this from developing, nitroglycerin-free intervals of 10-12 hours between doses are recommended. However, if you are experiencing chest pain, which is unrelieved by one nitroglycerin dose, it is acceptable to have another dose and call for urgent medical help.
  • May not be suitable for some people including seniors; those with a history of stroke or bleeding in the brain; with anemia, glaucoma, migraines, or swelling of the heart sac; taking medications for erectile dysfunction; or in people whose blood flow back to the heart is already restricted.
  • May interact with a number of other medications including medicines used to treat erectile dysfunction (such as sildenafil and tadalafil), topical anesthetics, antidepressants and antipsychotics, riociguat, diuretics, ergot derivatives, and tizanidine. Alcohol may increase the side effects of nitroglycerin. May affect the results of some medical tests.
  • Nitroglycerin can be toxic to children and pets. Keep well out of reach.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

4. Bottom Line

Nitroglycerin dilates veins, relieving chest pain and lowering blood pressure. It has a very short duration of action and may not be suitable for some people.

5. Tips

  • If you are taking this medicine to relieve symptoms of angina, keep it on hand at all times. Always refill your prescription before you run out of nitroglycerin.
  • Take nitroglycerin spray or sublingual tablets at the first sign of chest pain. Sit down if you can before taking a dose. Place the sublingual tablet under your tongue and allow it to dissolve slowly. Take exactly as directed by your doctor. Do not use more than three tablets in 15 minutes.
  • Nitroglycerin spray needs to be primed before use or if it has not been used for six weeks. Spray the dose of Nitrolingual preferably onto or under the tongue; do not inhale. Close your mouth after the spray. Avoid rinsing the mouth for five to ten minutes after. Keep the spray canister away from heat or flames because it may explode.
  • Talk to your doctor about taking nitroglycerin five to ten minutes before any activity that typically causes you chest pain.
  • If you develop severe chest pain or symptoms of a heart attack, or if your chest pain lasts more than five minutes, seek emergency medical attention.
  • Always sit or stand up slowly when rising from a lying down or seated position as nitroglycerin may cause a drop in blood pressure.
  • Contact your doctor immediately if you develop a slow heartbeat or new or worsening chest pain after using nitroglycerin.
  • Sometimes nitroglycerin will cause burning or stinging in your mouth, and sometimes it won't. Do not rely on this as an indication that the medicine is or isn't working, because it is an unreliable indication.
  • Tell other health professionals (such as your dentist) that you take nitroglycerin.
  • Do not take medicines for erectile dysfunction (ED), such as Viagra, Cialis or Levitra, while you are taking nitroglycerin as the combination may dangerously drop your blood pressure. Talk to your doctor or pharmacist before taking any other medications with nitroglycerin, because some may not be compatible with it.
  • Do not take nitroglycerin if you have circulation problems, are in shock, have severe anemia, or a feeling of pressure inside your head.

6. Response and Effectiveness

  • Nitroglycerin acts in the body for an extremely short period of time, although it is metabolized to longer-lived active metabolites. However, these are less effective vasodilators than nitroglycerin.

7. Interactions

Medicines that interact with nitroglycerin may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with nitroglycerin. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with nitroglycerin include:

  • antidepressants, such as amitriptyline, amoxapine, clomipramine
  • antipsychotics, such as aripiprazole, clozapine, haloperidol, nefazodone, or olanzapine
  • baclofen
  • benzodiazepines, such as alprazolam, clobazam, clonazepam, lorazepam, or oxazepam
  • bupropion
  • buspirone
  • erectile dysfunction medications such as avanafil, sildenafil, tadalafil, or vardenafil
  • heart medications, such as benazepril, captopril, diltiazem, felodipine, or verapamil
  • licorice
  • lithium
  • migraine medications, such as ergotamine or dihydroergotamine
  • minoxidil
  • opioids, such as alfentanil, codeine, fentanyl, hydrocodone, or morphine
  • Parkinson's disease medications, such as cabergoline, rasagiline, or selegiline
  • prilocaine
  • promethazine
  • tizanidine
  • zolpidem.

Note that this list is not all-inclusive and includes only common medications that may interact with nitroglycerin. You should refer to the prescribing information for nitroglycerin for a complete list of interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use nitroglycerin only for the indication prescribed.

Copyright 1996-2020 Revision date: March 23, 2020.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.