Nitroglycerin is taken under the tongue or sprayed onto it, not swallowed like a regular pill. It works by relaxing blood vessels to restore blood flow to the heart during an angina attack, and relief typically begins within one to three minutes. The most important rule: sit down before you take it, take no more than three doses spaced five minutes apart, and call for emergency help if your chest pain hasn’t improved after the third dose.
Sublingual Tablets: Step by Step
When chest pain or pressure begins, sit down immediately. Standing increases your risk of fainting because nitroglycerin lowers blood pressure. Place one tablet under your tongue or between your cheek and gum. Do not chew, crush, or swallow it. Let the tablet dissolve completely so the medication absorbs through the thin tissue in your mouth and enters your bloodstream directly.
If your pain hasn’t eased after five minutes, place a second tablet under your tongue the same way. Wait another five minutes. If the pain is still there, take a third tablet. Three tablets in 15 minutes is the maximum. If your chest pain persists after that third dose, you need emergency medical attention right away.
You may notice a slight tingling or burning sensation under your tongue as the tablet dissolves. Some people expect this as a sign the tablet is “working,” but modern formulations don’t always produce that feeling, so its absence doesn’t mean the medication is inactive.
Lingual Spray: Step by Step
The spray version delivers the same medication but in a fine mist. Before using a new canister for the first time, you need to prime it by spraying five times into the air, away from yourself and anyone nearby. If you haven’t used the spray in six weeks, prime it once. If it’s been longer than six weeks, you may need up to five priming sprays again.
To use it during an episode:
- Sit down and remove the plastic cover from the canister.
- Do not shake the container.
- Hold it upright with your forefinger on the grooved button.
- Open your mouth and bring the canister as close as possible.
- Press the button firmly to spray onto or under your tongue. Do not inhale the spray.
- Close your mouth and avoid swallowing for a few seconds. Don’t rinse your mouth or spit for 5 to 10 minutes.
If you need a second dose, wait five minutes and repeat. The same three-dose, 15-minute maximum applies to the spray just as it does to tablets.
Why Sitting Down Matters
Nitroglycerin widens blood vessels throughout your body, which drops your blood pressure. If you’re standing, that sudden drop can make you lightheaded or cause you to faint. Sitting (or even lying down with your head slightly elevated) keeps blood flowing to your brain while the medication works. Stay seated for a few minutes after the pain resolves before getting up slowly.
Common Side Effects
A headache after taking nitroglycerin is extremely common and happens for the same reason the drug relieves chest pain: it dilates blood vessels, including those in and around your brain. This headache typically peaks within minutes and fades within about 45 minutes. Other common side effects include a brief increase in heart rate, mild nausea, and feeling lightheaded or weak. These effects are temporary and generally resolve on their own as the medication wears off.
The Interaction With ED Medications
If you take medications for erectile dysfunction, the timing matters significantly. These drugs work through a similar blood-vessel-relaxing pathway, and combining them with nitroglycerin can cause a dangerous drop in blood pressure. Current guidelines from the American College of Cardiology and American Heart Association set specific windows you must respect:
- Sildenafil or vardenafil: Do not use nitroglycerin within 24 hours.
- Tadalafil: Do not use nitroglycerin within 48 hours. Research shows that even at the 24-hour mark, blood pressure still drops significantly lower than normal when the two drugs overlap.
- Avanafil: Do not use nitroglycerin within 12 hours.
If you experience chest pain during one of these windows, call emergency services rather than reaching for your nitroglycerin.
Storing Your Nitroglycerin Properly
Nitroglycerin is chemically unstable compared to most medications. In its pure form, it reacts with oxygen and breaks down when exposed to light. It also adsorbs to plastic and to the desiccant packets commonly found in pill bottles, meaning it can literally leach into those materials and lose potency.
Keep sublingual tablets in their original glass bottle with the cap screwed on tightly. Replace them every six months, even if you haven’t used any, because potency declines over time. Modern manufacturing has made the tablets more durable than older formulations, so carrying them in a pocket or purse is fine as long as you minimize the empty space in the container (less air means less degradation). Don’t transfer tablets to a plastic pillbox or a different container.
The spray canister is more shelf-stable than tablets because the medication is sealed from air exposure, but check the expiration date printed on it and replace it accordingly.
Using Nitroglycerin Before Physical Activity
If you have predictable angina triggered by exertion (climbing stairs, walking uphill, physical labor), your doctor may instruct you to take a dose a few minutes before the activity. The approach is the same: sit down, take one tablet or one spray, wait for it to take effect, then begin the activity. This preventive use can head off an episode before it starts, but the three-dose-per-15-minute limit still applies if chest pain develops anyway.