What is nitroglycerin?

For people with coronary artery disease whose arteries are clogged and narrowed by plaque, physical exertion can cause intense chest pain due to the heart’s demand for oxygen-rich blood. This chest pain is called angina. Nitroglycerin is an important medication to help treat chest pain.

Nitroglycerin is a nitrate, which is in a class of medications called vasodilators. Vasodilators do what they sound like: dilate the blood vessels by relaxing them, which improves the blood flow to the heart and reduces its workload.

Nitroglycerin can be used in a quick-acting form during a sudden incidence of angina or as a preventative against future symptoms.

Types of nitroglycerin

Nitroglycerin is available in different forms for specific uses. These are:

Quick-release forms of nitroglycerin included chewable or dissolvable tablets and oral sprays (sprayed on or under the tongue).  These nitroglycerin types should be taken during an instance of angina or just before physical activities that typically bring about angina, such as mowing the lawn, shoveling snow, playing sports, walking uphill, or having sexual intercourse.

For people with one or fewer angina episodes per week, quick-release tablets of nitroglycerin might make sense.

For those with two or more angina episodes per week, long-acting versions might be a safer option. When used on a long-term basis, nitroglycerin extended-release capsules, ointments, and skin patches can prevent angina from occurring. (They do not cure coronary artery disease and should not be treated as such.)

 How to use quick-acting nitroglycerin

Those prescribed quick-release nitroglycerin should keep the medication close at all times, such as in a vial on a necklace or keychain.  Because nitroglycerin relaxes veins and arteries, it lowers blood pressure, which can cause dizziness when occurring suddenly. Sit or lie down to take this medication and, if driving, stop your vehicle in case of fainting. Rest your feet on the ground for a few minutes and get up slowly.

Take only one dose and wait to see if symptoms are relieved. If symptoms get worse, call 911 immediately and stay on the phone with the emergency responder. Let your doctor know about all instances of angina to manage your medication effectively.

How to use long-lasting nitroglycerin

To prevent angina, ointments and patches can be applied once or twice a day, depending on your doctor’s instructions. Make sure to use the amount prescribed — measure the ointment carefully and use the correct number of patches at a time as prescribed by your doctor. Patches should be applied on the upper body and to a different area of the skin every day to prevent irritation and redness.

Nitroglycerin patches and ointment might not work as well after a long period. The body can develop tolerance to these drugs, so you need a nitrate-free period that lasts several hours at least once a day. Your doctor may start you on a lower dose and increase it as needed, and may schedule doses so that there are free periods in between. When taking off patches or removing ointment, wash the area with soap and water. If prescribed, you should continue using long-acting forms of nitroglycerin even if you feel better and have not had an episode of angina for a long time. Speak to your doctor before discontinuing use.

Nitroglycerin ointment can also be used to treat anal fissure pain. Nitroglycerin relieves pain using the same mechanism as it does to treat angina — by relaxing the blood vessels. This relaxation reduces pressure around the rectal area and helps decrease inflammation.

Nitroglycerin side effects

Some of the side effects include:

  • A warm or flushed feeling
  • Headache, dizziness, or lightheadedness
  • Burning or tingling sensation under your tongue (for sprays and dissolvables)
  • Redness or irritation of the skin (for ointments and patches)

More severe side effects include fainting, increased pain, a slow heartbeat, difficulty breathing or swallowing, or vomiting. Seek medical attention immediately if any of these symptoms occur.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help.

Medical history

Discuss your medical history with your health care provider before taking nitroglycerin. Certain medications can interact negatively with nitroglycerin. These include erectile dysfunction medications like Viagra, which can cause sudden decreases in blood pressure that can be fatal if mixed with nitroglycerin. Inform your doctor of other blood pressure medications, aspirin, and medicines to treat blood clots.

Medical conditions that may preclude you from using nitroglycerin include:

  • Low blood pressure
  • Heart failure
  • Hypertrophic cardiomyopathy (thickening of the heart muscle)
  • Current or planned pregnancy
  • Previous stroke
  • Previous heart attack
  • Liver or kidney disease
  • Overactive thyroid
  • Frequent migraines
  • Anemia
  • Glaucoma

How to store nitroglycerin

Nitroglycerin tablets are sensitive to environmental elements, so it’s important to keep the bottle tightly closed and in a cool, dry place (not a warm, humid bathroom). The tablets lose effectiveness and expire a few months after opening, so pay attention to the expiration date and refill the prescription when needed.

Nitroglycerin ointment tubes should be closed tightly after each use and disposed of 8 weeks after opening.

What to avoid when taking nitroglycerin

Smoking decreases nitroglycerin’s effectiveness and should be avoided. Alcohol can increase the risk of dizziness. Avoid driving a car, or operating heavy machinery, or taking part in any activity that requires mental clarity when taking quick-release forms of the nitroglycerin until you know how the medication affects you.