Nitrostat Side Effects: What to Expect and When to Call Your Doctor

Nitrostat (nitroglycerin sublingual tablets) works quickly and powerfully to relieve angina — but those same mechanisms that relax blood vessels and improve blood flow to the heart can also cause side effects. Knowing what to expect helps you use Nitrostat safely and confidently.

The Most Common Nitrostat Side Effects

The most frequently reported side effects of Nitrostat — occurring in more than 2% of patients per FDA labeling — are:

Headache: The most common side effect of nitroglycerin. It occurs because the drug dilates blood vessels, including those in the brain. Headaches are often described as throbbing and typically occur within minutes of taking the tablet. They usually decrease in severity with continued use.

Dizziness: Caused by a drop in blood pressure as the drug takes effect. This is why you should always sit or lie down when taking Nitrostat.

Paresthesia: A tingling or burning sensation, often felt under the tongue where the tablet dissolves. This is normal and does not indicate a problem.

Flushing: A warm feeling or redness in the face and neck due to blood vessel dilation. This is expected and usually short-lived.

Nausea: Less common but can occur, particularly with higher doses.

Headache: Is It Normal?

Yes — nitroglycerin headache is a well-known effect and is actually used by some patients as a way to verify that their tablets are still potent. If you take Nitrostat and do NOT get a headache (and it also doesn't relieve your chest pain), the tablets may have lost their potency.

Headaches from nitroglycerin tend to improve with continued use and are usually manageable with acetaminophen (Tylenol). Do not take NSAIDs (ibuprofen, naproxen) for the headache without checking with your doctor, as they can interact with cardiovascular medications.

Low Blood Pressure: The Serious Risk

Nitrostat can cause a significant drop in blood pressure — this is called hypotension. For most people, this is mild and manifests as dizziness when standing up too quickly (orthostatic hypotension). But in some situations, the blood pressure drop can be severe:

If you have taken a PDE-5 inhibitor (sildenafil/Viagra, tadalafil/Cialis, vardenafil/Levitra, or avanafil/Stendra) in the past 24–48 hours — this combination is contraindicated and can cause fatal hypotension.

If you are dehydrated, standing up quickly, or have pre-existing low blood pressure

If you drink alcohol while taking Nitrostat — alcohol has additive blood pressure-lowering effects

Always sit or lie down when taking Nitrostat and remain seated for several minutes after use. Rise slowly to prevent dizziness and falls.

Serious Side Effects: When to Seek Emergency Help

Call 911 immediately if you experience:

Chest pain that does not improve after 3 doses of Nitrostat in 15 minutes

Severe dizziness or fainting (syncope)

Severe or pounding headache unlike your usual nitroglycerin headache

Blue lips or fingernails, severe weakness, or difficulty breathing

Signs of methemoglobinemia (rare): chocolate-brown blood coloration, blue-tinted skin, confusion, extreme fatigue

Tolerance: Does Nitrostat Stop Working?

Unlike long-acting nitrates (patches, mononitrate), Nitrostat sublingual tablets are used only as needed — not continuously — so clinically significant tolerance is much less of a concern. Patients who use it too frequently may develop tolerance, which is why it's important to only use Nitrostat when needed and not as a first-line substitute for optimizing preventive therapy.

When the Tablet Doesn't Seem to Be Working

If you take Nitrostat and your chest pain does not improve within 5 minutes, take a second tablet. If pain persists after a third tablet (15 minutes total), call 911. A Nitrostat tablet that causes no headache and no relief may have lost its potency — check the expiration date and whether the bottle has been open for more than 6 months.

For information on drug interactions with Nitrostat, see: Nitrostat Drug Interactions: What to Avoid and What to Tell Your Doctor. If you need help finding Nitrostat at a pharmacy near you, visit medfinder.com.