Nitroglycerin belongs to the class of medications called anti-anginals. Nitroglycerin is used to relieve acute attacks of angina (chest pain). Nitroglycerin relieves acute angina attacks by relaxing blood vessels and increasing the oxygen and blood supply to the heart.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

To use this medication, spray it once or twice (as directed by your doctor) onto or under the tongue at the first sign of an angina attack. Do not inhale. The dose may be repeated twice with at least a five minute interval between each dose, or as directed by your doctor. If relief is still not obtained after three doses of nitroglycerin (i.e., 15 minutes), seek medical help immediately.

While using nitroglycerin spray, remain at rest in a sitting position and keep the container vertical with the nozzle head up. Place the opening in the nozzle head as close to the mouth as possible. Avoid getting the spray in your eyes.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is very important to use this medication exactly as prescribed by your doctor.

Store nitroglycerin spray at room temperature (15°C to 30°C) away from hot water, radiators, or other sources of heat. Do not incinerate the canister and do not attempt to open it. Keep it out of reach of children.

Do not use nitroglycerin spray if you:

• are allergic to nitroglycerin or to any of the ingredients of the medication
• are allergic to other nitrates
• have extremely low blood pressure
• have severe anemia
• have heart failure
• have increased eye pressure (glaucoma)
• have increased pressure within the head (e.g., after an accident)
• are having a heart attack
• are taking the medication riociguat
• are taking phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)

People who use nitroglycerin regularly or intermittently should not use phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, or vardenafil) because a life-threatening lowering of blood pressure can result.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• dizziness or lightheadedness, especially when getting up from a lying or sitting position
• fast heartbeat
• flushing of the face and neck
• headache
• nausea or vomiting
• rash
• restlessness
• runny nose
• sore throat or mouth
• weakness

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abdominal pain
• blurred vision
• dryness of mouth
• fainting
• headache (severe or prolonged)
• signs of low blood pressure (e.g., dizziness, lightheadedness, fainting)
• sweating
• swelling of the ankles
• tingling or pins and needles of the arms or legs
• vomiting

Contact a doctor at once if any of the following signs of overdose occur:

• bluish-coloured lips, fingernails, or palms of the hands
• dizziness (extreme) or fainting
• shortness of breath
• unusual tiredness or weakness
• weak and fast heartbeat

Stop taking the medication and seek immediate medical attention if any of the following occur:

• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
• continued chest pain

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Dizziness: This treatment may cause temporary dizziness. Do not drive, operate machinery, or perform other hazardous tasks until you have determined how this medication affects you.

Low blood pressure: Headaches or symptoms of low blood pressure, such as weakness or dizziness, particularly when getting up suddenly from a lying or sitting position, may result from taking too much nitroglycerin. If these symptoms occur, your doctor may reduce the dose or stop the use of nitroglycerin. People who might be negatively affected by low blood pressure should use nitroglycerin spray with caution. People who take diuretics or have pre-existing low blood pressure may be at more risk of experiencing low blood pressure. Discuss any concerns you might have with your doctor.

Medical conditions: The benefits and safety of nitroglycerin spray for people who have an acute heart attack or congestive heart failure have not been established.

Tolerance: Nitroglycerin users may develop tolerance to the medication, resulting in it not working as well. Tolerance to other nitrates or nitrites can also happen, especially if long-acting nitrates are being used at the same time. As tolerance to nitroglycerin develops, the effect of fast-acting sublingual (under the tongue) nitroglycerin is somewhat reduced.

Pregnancy: This medication has not been studied for use by pregnant women. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known whether this medication passes into breast milk. If you are breast-feeding and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of this medication for children have not been established.

There may be an interaction between nitroglycerin and any of the following:

• alcohol
• aldesleukin
• aliskiren
• alpha-agonists (e.g., clonidine, methyldopa)
• alpha-blockers (e.g., alfuzosin, doxazosin, tamsulosin)
• amiodarone
• angiotensin converting enzyme inhibitors (ACEIs; captopril, enalapril, ramipril)
• angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
• anti-psychotics (e.g., clozapine, olanzapine, quetiapine, risperidone)
• apomorphine
• barbiturates (e.g., butalbital, phenobarbital)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• bortezomib
• brimonidine
• bromocriptine
• cabergoline
• calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
• conivaptan
• diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
• duloxetine
• ergot alkaloids (e.g., dihydroergotamine, ergotamine, methylergonavine)
• guanfacine
• hydralazine
• iron sucrose
• levodopa
• minoxidil
• morphine
• nabilone
• nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate0
• obinutuzumab
• pentoxifylline
• phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
• pramipexole
• rasagiline
• riociguat
• ropinirole
• rosiglitazone
• rotigotine
• sacubitril
• selegiline
• sotalol
• tamsulosin
• tizanidine
• tricyclic antidepressants (e.g., amitriptyline, imipramine, nortriptyline)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.