How does this medication work? What will it do for me?

Nitroglycerin belongs to the class of medications called antianginals. Nitroglycerin sublingual (under the tongue) tablets are used to relieve acute attacks of angina (chest pain). This medication can also be used to prevent an acute attack if taken in advance of an activity that would normally cause an angina attack. Nitroglycerin relieves and prevents acute angina attacks by relaxing blood vessels and increasing the oxygen and blood supply to the heart.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. 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.

What form(s) does this medication come in?

0.3 mg
Each small, round, white sublingual tablet, marked with "N" on one side and the number "3" on the other side, contains nitroglycerin 0.3 mg. Nonmedicinal ingredients: calcium stearate, glyceryl monostearate, lactose monohydrate, pregelatinized starch, and silicon dioxide. Gluten-, paraben-, sodium-, sulfite-, and tartrazine-free.

0.6 mg
Each small, round, white sublingual tablet, marked with "N" on one side and the number "6" on the other side, contains nitroglycerin 0.6 mg. Nonmedicinal ingredients: calcium stearate, glyceryl monostearate, lactose monohydrate, pregelatinized starch, and silicon dioxide. Gluten-, paraben-, sodium-, sulfite-, and tartrazine-free.

How should I use this medication?

To use nitroglycerin sublingual tablets, place a tablet under your tongue at the first sign of an angina attack. The dose may be repeated twice with at least a 5-minute interval between each dose, or as directed by your doctor. If relief is still not obtained after 3 doses of nitroglycerin (i.e., 15 minutes), seek medical help immediately.

While using nitroglycerin sublingual tablets you should be resting, preferably in a sitting position.

As directed by your doctor, the sublingual (under the tongue) tablet may be used 5 to 10 minutes before engaging in activities that may cause angina.

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 take this medication exactly as prescribed by your doctor.

Keep this medication away from moisture and out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Nitroglycerin sublingual tablets should not be taken by anyone who:

  • is allergic to nitroglycerin or to any of the ingredients of the medication
  • is allergic to other nitrates
  • has extremely low blood pressure
  • has increased eye pressure (glaucoma)
  • has increased pressure within the head (e.g., after an accident)
  • has severe anemia

People who use nitroglycerin regularly or intermittently should not use erectile dysfunction medications called PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) because a life-threatening lowering of blood pressure can result.

What side effects are possible with this medication?

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 sitting or lying down position
  • fast heartbeat
  • flushing of the face and neck
  • headache
  • nausea or vomiting
  • restlessness

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:

  • blurred vision
  • dry mouth
  • headache (severe or prolonged)

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

  • bluish-coloured lips, fingernails, or palms of hands
  • convulsions (seizures)
  • dizziness (extreme) or fainting
  • feeling of extreme pressure in head
  • fever
  • shortness of breath
  • unusual tiredness or weakness
  • weak and fast heartbeat

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.

Are there any other precautions or warnings for 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.

Low blood pressure: Headaches or symptoms of low blood pressure such as weakness or dizziness, particularly when getting up from a sitting or lying down 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 sublingual tablets with caution. People who take diuretics or have preexisting low blood pressure may be at more risk of being negatively affected.

Medical conditions: The benefits and safety of nitroglycerin sublingual tablets 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 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. Be sure to tell your doctor if you are pregnant or planning to become pregnant.

Breast-feeding: It is not known if this medication passes into breast milk. Be sure to discuss with your doctor the risks and benefits of using this medication before breast-feeding.

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

What other drugs could interact with this medication?

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

  • alcohol
  • alteplase
  • dihydroergotamine
  • erectile dysfunction medications called PDE-5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
  • medications that cause dry mouth
  • medications that reduce blood pressure (e.g., vasodilators, calcium channel blockers, ACE inhibitors, beta-blockers, diuretics)
  • tricyclic antidepressants

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.