Can nitroglycerin ointment cause headaches? Understanding a Common Side Effect

October 9, 2025 •

4 min read

Clinical trials have shown that headaches are one of the most most frequent side effects of nitroglycerin ointment, affecting more than 60% of patients in some studies. While potentially bothersome, this head pain is a well-known consequence of the medication's vasodilatory effects.

Quick Summary

Nitroglycerin ointment can cause dose-related headaches because its vasodilatory action widens blood vessels. Headaches often lessen with continued use as the body develops tolerance, and they can be managed with physician-recommended pain relief.

Key Points

Common Side Effect: Headaches are a very common adverse effect of nitroglycerin ointment and are often a sign that the medication is active.
Vasodilation is the Cause: The headaches are caused by the medication's widening of blood vessels in the head, a direct result of its mechanism of action.
Tolerance Often Develops: With continued use, many patients build a tolerance to this effect, and the headaches typically become less frequent and severe within a few days or weeks.
Management is Possible: Over-the-counter pain relievers like acetaminophen are often recommended for relief, and cold compresses can also be effective.
Do Not Stop Treatment: Patients should not stop using the ointment or alter their dose to avoid headaches without first speaking to a doctor, as this can reduce the medication's efficacy.
Seek Medical Advice for Severity: Contact a doctor for severe, persistent, or worsening headaches, or for other worrying symptoms like intense dizziness or vision changes.

The Link Between Nitroglycerin and Headaches

Nitroglycerin is a vasodilator, a type of medication that works by relaxing and widening blood vessels throughout the body. This mechanism is key to its therapeutic effects, such as reducing chest pain (angina) or alleviating pain from chronic anal fissures. However, this same process extends to other blood vessels, including those in the head, and it is this widening of cranial blood vessels that triggers a headache.

The Role of Nitric Oxide

Nitroglycerin works by being converted into nitric oxide (NO) within the body. Nitric oxide is a potent signaling molecule that activates a cascade leading to vascular smooth muscle relaxation and vasodilation. In the head, this dilation of blood vessels is what causes the throbbing or pulsating pain characteristic of a nitrate-induced headache. For many patients, the presence of a headache can actually be a sign that the medication is working as intended.

Duration and Tolerance of Nitroglycerin Headaches

The timing and severity of nitroglycerin headaches can vary. Some patients experience an immediate headache, which is typically mild to moderate and resolves spontaneously within about an hour. Others may experience a delayed, more severe headache that can be migraine-like in nature and may not appear until several hours after application.

For many, these headaches are a temporary side effect. The body often develops a tolerance to the vasodilatory effects of nitroglycerin with continued use. This means that the frequency and intensity of the headaches can decrease significantly over the first few days or weeks of treatment. Patients should be aware of this and avoid altering their dosage schedule to prevent headaches, as doing so could compromise the medication's effectiveness.

Management and Relief for Nitroglycerin Headaches

If you experience headaches from nitroglycerin ointment, several strategies can help manage the discomfort. It is important to consult your doctor before beginning any new treatment or making changes to your regimen.

Over-the-Counter Pain Relievers

Acetaminophen (Tylenol): This is often the first-line recommendation for managing nitroglycerin headaches.
Aspirin: In some cases, a doctor may recommend aspirin for more severe pain, but this should be discussed with your healthcare provider.

Simple and Effective Lifestyle Tips

Stay Hydrated: Drinking plenty of fluids can help mitigate some of the side effects of nitrates.
Avoid Alcohol: Alcohol consumption can exacerbate the vasodilatory effects of nitroglycerin, potentially worsening dizziness and hypotension.
Use Cold Compresses: Applying a cold compress to the forehead or temples can help constrict blood vessels and reduce pain. A study found that cold compresses applied at the start of treatment helped prevent headaches in some patients.
Get Enough Sleep and Rest: Rest is crucial for recovery from any headache, including those caused by medication. Reducing exposure to bright lights and strong smells may also provide relief.

When to Contact a Healthcare Provider

While headaches are a common side effect, you should contact your doctor or seek immediate medical attention if you experience any of the following:

The headaches are severe or unbearable and do not respond to over-the-counter pain relievers.
You experience extreme dizziness, lightheadedness, or blurred vision that does not improve.
You notice swelling of the face, lips, or tongue, or have difficulty breathing, which could indicate a serious allergic reaction.
You experience changes in your heart rate, such as a fast, irregular, or slow heartbeat.
The headaches persist or worsen over time instead of improving.

Comparison of Headache Management Strategies


Strategy	Mechanism	Recommended Timing	Considerations
Acetaminophen	Provides general pain relief without further affecting blood vessels.	For pain relief after a headache has started.	Consult a doctor for proper dosage and use with other medications.
Cold Compresses	Constricts blood vessels in the head, potentially reducing pain.	Can be used preventatively at the start of treatment or for relief after onset.	Simple, effective, and free of side effects.
Stay Hydrated	Helps stabilize blood pressure and reduce the risk of dizziness.	Throughout the day while on medication.	Avoids aggravating the medication's hypotensive effects.
Dose Adjustment	Reduces the overall vasodilatory effect of the medication.	Considered by a doctor if headaches are severe and persistent.	Do not adjust dosage on your own; only with a doctor's supervision.

Conclusion

Yes, nitroglycerin ointment can cause headaches, and this is a common and expected side effect due to the medication's vasodilating properties. The good news is that these headaches are often temporary, with many patients developing a tolerance as their body adjusts to the treatment. Effective strategies like over-the-counter pain relievers, cold compresses, and proper hydration can help manage the discomfort. Crucially, patients should never alter their medication dosage without consulting a healthcare provider, as this can affect the medication's efficacy. For persistent or severe headaches, or any other concerning symptoms, always seek guidance from your doctor to ensure your treatment remains both effective and safe.

Visit MedlinePlus for more information about nitroglycerin and other medications.

Frequently Asked Questions

Nitroglycerin ointment is a vasodilator, meaning it widens blood vessels. This effect is caused by the release of nitric oxide. When blood vessels in the head dilate, it can trigger a headache.

Yes, for many patients, a headache can be a signal that the medication is having its intended vasodilatory effect throughout the body. It does not necessarily indicate a problem.

The duration can vary. Some mild headaches may last less than an hour, while more severe, delayed headaches can last longer. Headaches often become less severe and frequent over the first few days of treatment as tolerance develops.

Yes, simple pain relievers like acetaminophen (Tylenol) are often recommended. However, you should always consult your healthcare provider before taking any medication for relief.

No, you should not stop or change your dosage schedule on your own. Altering the medication can reduce its effectiveness. If the headaches are unbearable, talk to your doctor about management strategies or dose adjustment.

Immediate headaches are generally mild to moderate, occurring soon after application and lasting about an hour. Delayed headaches are more severe and migraine-like, appearing several hours after the dose, especially in patients with a history of migraines.

Yes, some studies suggest that applying a cold compress to the head can help prevent or reduce the severity of nitroglycerin-induced headaches by constricting blood vessels.