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Nitrates (Nitroglycerin)

What does this medication do?
Nitrates can be used to prevent chest pain (angina), limit the number of angina attacks that you have, relieve the pain of a current attack, or treat the symptoms of heart failure. Nitroglycerin is a type of nitrate.

How does it work?
Nitrates are vasodilators, which means they help widen (dilate) your blood vessels, making it easier for blood to flow through and let more oxygen-rich blood reach your heart. Better blood flow means your heart doesn't have to work as hard. Nitrates also relax the veins so less blood is returned to the heart, which can reduce the workload on your heart.

How should I take it?
There are several different forms of nitrates:

  • Pills: sublinguals (held under your tongue).
  • Topical ointment or transdermal patches deliver nitrates through your skin.
  • Sublingual spray is sprayed on or under your tongue.

Always talk to your doctor or pharmacist about how and when to take your specific medication.

What should I avoid while taking this medicine?
You should avoid smoking while you are taking nitrates since it may make them less effective. You should also avoid alcohol, because it may increase the effect of the medicine.

What if I am taking other medicines?
Nitrates can interact with other medications, so be sure to tell your doctor about any other medications you may be taking including prescription, non-prescription, over-the-counter or natural health products (vitamins and minerals, herbal remedies, homeopathic medicines, traditional medicines such as traditional Chinese medicines, probiotics and other products such as amino acids and essential fatty acids).

Some medications that may cause an interaction include:

  • Viagra® (sildenafil). Viagra should not be taken within 24 hours of taking nitrates. When combined with nitrates, Viagra may cause lowered blood pressure, dizziness, lightheadedness, fainting or more serious effects. Check with your doctor or pharmacist about similar drugs or herbal remedies that treat erectile dysfunction.
  • Medicines to treat high blood pressure.
  • Certain heart medicines.
  • Over-the-counter cough, cold, and flu medicines.
  • Over-the-counter herbal cough, cold, and flu medicines.

Speak to your doctor or pharmacist about any other information you may need to know about your medications.

What else should I tell my doctor?
Always give your doctor your complete medical history, especially if you are over 60 years of age, have recently had a stroke or heart attack or have severe headaches, low iron (anemia) or glaucoma. You may also want to talk to your doctor about how effective nitrates are for managing your angina. Your doctor can adjust the amount of medicine or suggest other ways of managing your condition.

What are some common side effects?
Some common side effects of nitrates include headaches, flushing, dizziness, fainting, low blood pressure (hypotension) and irregular heart rhythms (arrhythmia). Report any and all side effects to your doctor.

Lifestyle changes
Eating a healthy diet that is lower in fat, especially saturated and trans fats, being smoke free, limiting alcohol use, being physically active and reducing stress are also important to lowering the risk of heart disease. Talk to your healthcare practitioner about how you can achieve these lifestyle changes.

For more information
Health Canada provides health and medical information to help Canadians maintain and improve their health. Learn more about Safe Use of MedicinesSafety and Effectiveness of Generic Drugs and Buying Drugs over the Internet.

Drug Product Database provides information about drugs approved for use in Canada.

MedEffect Canada provides safety alerts, public health advisories, warnings and recalls.

Your ministry of health also provides useful health resources in your province or territory. For example, Ontario has a MedsCheck program providing free pharmacist consultations on safety use of drugs. British Columbia has a Senior Healthcare webpage providing information about important health programs.  

Last modified: July 2011
Last reviewed: July 2011