Monoket (Isosorbide Mononitrate) - Oral

What Is Monoket?

Monoket (isosorbide mononitrate) is a prescription drug used to prevent chest pain (angina) in people with heart problems (coronary artery disease).

This medication is in a class of drugs called nitrates. Nitrates allow blood to flow more easily by relaxing your blood vessels (arteries and veins). This widening of blood vessels relieves the stress on your heart muscles, and therefore you will experience less chest pain.

Monoket will not work fast enough to treat sudden chest pain attacks. It is important to know that it is not generally recommended to use Monoket for rapid or immediate chest pain relief.

Monoket is available as an oral medication in tablet form.

Drug Facts

Generic Name: Isosorbide mononitrate

Brand Name(s): Monoket

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Nitrate

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Isosorbide mononitrate

Dosage Form(s): Tablet

What Is Monoket Used For?

The Food and Drug Administration (FDA) approved Monoket to prevent chest pain caused by coronary artery disease. 

Coronary artery disease typically happens when insufficient blood and oxygen is delivered to your heart. This could result from the formation of plaques in your arteries and lead to atherosclerosis. The blockage of the arteries can restrict your blood flow, and consequently you will experience chest pain from not receiving enough oxygen-rich blood.

Monoket is NOT intended for immediate or rapid relief of sudden chest pain (angina pectoris) because the onset of effect is not fast enough to help with a sudden attack.

How to Take Monoket

You should always follow the directions from your healthcare provider on how to take Monoket. Do not use this medication unless you understand how to use it correctly.

There are two formulations of isosorbide mononitrate: immediate-release (IR) and extended-release (ER). Monoket is available in IR formulations, whereas isosorbide mononitrate is available generically in both IR and ER forms.

IR forms have a faster onset but a shorter duration of effect. ER forms have a slower onset but a sustained duration of effect.

In general, immediate-release tablets are given twice a day. The second dose is usually given seven hours after the first dose to decrease the buildup of the drug to avoid developing a tolerance. Building drug tolerance would make the drug less effective and reduce the benefits you can get from it.

ER tablets are usually given only once daily due to their prolonged effect. Swallow the ER tablet whole. Do not crush, break, or chew it. ER tablets that are scored may be cut in half as needed.

It is important to take the drug regularly to benefit from it. To help you remember, take it at the same time every day. Do not change the dosing times unless directed by your healthcare provider.

Do not stop taking this medication unless told by your healthcare provider, even if you feel better. Your healthcare provider will need to slowly decrease your dose before stopping it completely.

Contact your pharmacist for a refill at least one week before you run out of the medication.


Store Monoket at room temperature (between 68 F and 77 F) in a dry place, away from moisture, heat, or sunlight. Keep it out of reach of children or pets to prevent accidental consumption.

Do not flush expired or unused medication down the toilet. Check with your local pharmacies if you have questions about the best way to throw out drugs, or visit the FDA's website to know where and how to discard all unused and expired drugs. You can also find disposal boxes in your area.

Off-Label Uses

Healthcare providers may prescribe isosorbide mononitrate for off-label uses, meaning for conditions not specifically indicated by the FDA. Off-label uses include:

  • Cervical ripening procedure: Though uncommon, isosorbide mononitrate might be used in the process of softening and dilating the cervix during labor induction. 
  • Prevention of esophageal variceal rebleeding: Isosorbide mononitrate might be used to prevent future bleeding from esophageal varices.

This is not an all-inclusive list of the reasons why a healthcare provider may prescribe this medication. Please check with your healthcare provider if you have any questions.

How Long Does Monoket Take to Work?

Monoket is generally absorbed in your body rapidly, within 30 to 45 minutes. IR tablets can last up to six hours, and ER tablets can last up to 24 hours.

However, it will not work fast enough to produce relief for an acute attack of chest pain. You will not benefit from this treatment unless you continuously use it as prescribed. It is important to take Monoket regularly to prevent a future attack of chest pain.

What Are the Side Effects of Monoket?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at online or by phone at 1-800-FDA-1088.

Common Side Effects

The most common side effects of Monoket are listed below:

  • Dizziness
  • Fatigue
  • Headache 
  • Stomach pain
  • Diarrhea
  • Nausea
  • Flushing (redness of the face or neck)

Tell your healthcare provider if these symptoms worsen or do not go away.

Severe Side Effects

Call your healthcare provider immediately if you have serious side effects. Dial 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Signs of an allergic reaction like rash, hives, or difficulty breathing
  • Severely irregular heartbeat (pounding heartbeats)
  • Severe dizziness or fainting (syncope)
  • Abnormal heartbeat (fast or slow)
  • Worsening of chest pain or experiencing new chest pain
  • Change in vision, eye pain, or irritation

Long-Term Side Effects

Nitrates are known sometimes to cause headaches. However, this is usually a sign that the medication is working. Do not stop your treatment if this happens. Instead, talk to your healthcare provider about ways to mitigate headache pain. They may recommend medications such as acetaminophen or ibuprofen.

Monoket may also cause dizziness. Avoid drinking or doing tasks requiring constant attention until you know how this medication will affect you. You might feel lightheaded when you change your position (from lying to sitting or from sitting to standing). Stand or sit up slowly to avoid postural or orthostatic hypotension. Drinking alcohol may make these symptoms worse.

Report Side Effects

Monoket may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program online or by phone (800-332-1088).

Dosage: How Much Monoket Should I Take? 

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For prevention of angina:
    • For oral dosage form (extended-release tablets):
      • Adults—At first, 30 or 60 milligrams (mg) once a day. Take the dose in the morning right after you wake up. Your doctor may increase your dose as needed.
      • Children—Use and dose must be determined by your doctor.
    • For oral dosage form (tablets):
      • Adults—20 milligrams (mg) two times a day. Take the first dose in the morning right after you wake up, and the second dose 7 hours later.
      • Children—Use and dose must be determined by your doctor.

Dose Modifications

If you are an adult over 65 years of age, talk to your healthcare provider and discuss if any dose adjustment is needed to reduce the risk of side effects such as dizziness. 

Data are limited concerning Monoket's safety and effectiveness in children, pregnant people, or those who are breastfeeding. However, it is recommended to talk with your prescriber to determine whether to take this medication, given the potential benefits versus risks.

It is recommended to talk to your healthcare provider if you have any questions about doses or uses. 

Missed Dose

If you miss a dose, take it as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take two doses at the same time or extra doses.

Overdose: What Happens If I Take Too Much Monoket?

If you happen to take too much Monoket, call your healthcare provider immediately. Call 911 or go to the nearest emergency room if you feel like you are having a life-threatening event.

An overdose of Monoket can be dangerous. Common symptoms of an overdose may include:

  • Severe or persistent dizziness
  • Confusion
  • Fainting
  • Severe headache
  • Pounding heartbeats
  • Trouble breathing
  • Sweating
  • Seizure

What Happens If I Overdose on Monoket?

If you think you or someone else may have overdosed on Monoket, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Monoket, call 911 immediately.


Drug Content Provided and Reviewed by IBM Micromedex®

If you will be taking this medicine for a long time, it is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Do not take riociguat (Adempas®), sildenafil (Viagra®), tadalafil (Cialis®), or vardenafil (Levitra®) while you are using this medicine. Using these medicines together may lower your blood pressure and cause blurred vision, dizziness, lightheadedness, or fainting. If you are taking these medicines and you experience an angina attack, you must go to the hospital right away.

This medicine may cause headaches. These headaches are a sign that the medicine is working. Do not stop using the medicine or change the time you use it in order to avoid the headaches. If you have severe pain, talk with your doctor.

Dizziness, lightheadedness, or faintness may occur, especially when you get up quickly from a lying or sitting position. Getting up slowly may help.

Dizziness, lightheadedness, or fainting is also more likely to occur if you drink alcohol, stand for long periods of time, exercise, or if the weather is hot. While you are taking this medicine, be careful to limit the amount of alcohol you drink. Also, use extra care during exercise or hot weather or if you must stand for long periods of time.

Do not stop using this medicine without checking first with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely.

Make sure any doctor or dentist who treats you knows that you are using this medicine. You may need to stop using this medicine several days before you have medical tests.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Monoket?

Tell your healthcare provider if any of the following apply to you. You may not be able to take Monoket if you:

  • Are allergic to isosorbide mononitrate or other nitrates
  • Have certain cardiovascular diseases (such as heart attack or heart failure)
  • Are also taking phosphodiesterase-5 (PDE-5) inhibitors (such as Viagra (sildenafil) or Cialis (tadalafil))
  • Have significantly low blood pressure
  • Have high pressure within the skull or bleeding in the brain

This medication is not intended for the immediate relief of sudden attacks of chest pain.

What Other Medications Interact With Monoket?

Before starting Monoket, talk to your healthcare provider about all prescription and over-the-counter (OTC) medications, vitamins, and herbal supplements you take.

Certain medications can increase the effects of nitrates and further decrease your blood pressure, putting you at risk for increased side effects, such as dizziness, fatigue, and fainting. These medications include:

  • PDE-5 inhibitors (e.g., sildenafil, tadalafil), which are commonly prescribed for erectile dysfunction but also widen and dilate your blood vessels
  • Adempas (riociguat), which is commonly used for pulmonary hypertension
  • High blood pressure medications, such as Zestril (lisinopril), Vasotec (enalapril), and Cozaar (losartan)

It is best to avoid taking these medications at the same time as Monoket or other nitrates. If both medications are needed, talk to your healthcare provider about the risks versus benefits of taking them together. They may closely monitor your response during treatment.

What Medications Are Similar?

Monoket is a nitrate commonly used to prevent attacks of chest pain (angina pectoris).

Other nitrates include Isordil (isosorbide dinitrate) and nitroglycerin. Like other nitrates, these medications relax the muscle in your blood vessels and allow oxygen and blood to flow more efficiently. 

Non-nitrate drugs that may also be used for chest pain include:

  • Beta-blockers (e.g., Tenormin (atenolol) and Inderal LA (propranolol)) slow down and reduce the workload of your heart. 
  • Calcium antagonists (e.g., Cardizem (diltiazem) and Verelan (verapamil)) prevent contraction of the smooth muscle in your blood vessels and allow oxygen and blood to flow through more easily.

Using Monoket for rapid or immediate chest pain relief is not recommended. One of the common examples of a fast-acting nitrate you might see for this use is sublingual (under the tongue) nitroglycerin.

Other medications may also be prescribed for these conditions. Please consult your healthcare provider for more details or if you have further questions. 

Frequently Asked Questions

  • Can I travel with Monoket?

    There is no current TSA restriction for traveling on a plane with Monoket. It is important to get your medication refilled before traveling.

  • What is the difference between the immediate-release (IR) and extended-release (ER) versions of isosorbide mononitrate?

    The IR formulation works faster but stays in your body for a shorter amount of time. This is the reason why you need to take Monoket IR twice daily. 

    The ER formulation works more slowly but stays in your body longer. As a result, you need to take ER tablets only once daily.

  • Will Monoket affect my blood pressure?

    Monoket, just like other nitrates, can decrease your blood pressure. It is usually not a problem for most people unless you also take PDE-5 inhibitors (e.g., sildenafil, tadalafil), riociguat, or other blood-pressure-lowering medications.

    Drinking alcohol can also increase the effect on your blood pressure. Check with your healthcare providers if you have any questions about your blood pressure or drug interactions. 

  • What is the difference between Monoket (isosorbide mononitrate) and Nitrostat (nitroglycerin)?

    Although both medications are nitrates, they can be used for different purposes. Monoket works slower and is used to prevent attacks of chest pain. It is not intended to treat a sudden episode. On the other hand, Nitrostat (nitroglycerin) works very fast and can be used to relieve your symptoms during a sudden attack.

How Can I Stay Healthy While Taking Monoket?

If you are prescribed Monoket, follow the directions given by your healthcare provider on how to take your medication correctly.

Tell your healthcare provider about all prescription and OTC medications, vitamins, and herbal supplements you take. It's recommended to avoid erectile dysfunction medications (PDE-5 inhibitors), alcohol, or riociguat while taking Monoket.

Continue taking your medication as prescribed, even if you feel fine. This means the medication is working to prevent your symptoms. If you suddenly stop taking it, you may experience a sudden angina attack.

Tell your healthcare provider or seek immediate medical help if you experience severe dizziness, headache, fainting, change of vision, abnormal heartbeats, or worsening chest pain.

Along with taking this medication daily, it is also important to eat a healthy diet, exercise as tolerated, and drink plenty of fluids as recommended by your healthcare provider.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

The author would like to recognize and thank Yufeng Zhai for contributing to this article. 

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. DailyMed. Label: Monoket- isosorbide mononitrate tablet.

  2. Dalen JE, Alpert JS, Goldberg RJ, Weinstein RS. The epidemic of the 20th century: coronary heart disease. Am J Med. 2014;127(9):807-812.

  3. DailyMed. Label: Isosorbide mononitrate tablet, extended release.

  4. Ghosh A, Lattey KR, Kelly AJ. Nitric oxide donors for cervical ripening and induction of labour. Cochrane Database Syst Rev. 2016;12(12):CD006901. doi:10.1002/14651858.CD006901.pub3.

  5. Gluud LL, Langholz E, Krag A. Meta-analysis: isosorbide-mononitrate alone or with either beta-blockers or endoscopic therapy for the management of oesophageal varices. Aliment Pharmacol Ther. 2010;32(7):859-871. doi:10.1111/j.1365-2036.2010.04418.x.

  6. Gruber HJ, Bernecker C, Lechner A, et al. Increased nitric oxide stress is associated with migraine. Cephalalgia. 2010;30(4):486-492. doi: 10.1111/j.1468-2982.2009.01964.x

  7. Food and Drug Administration. Nitrostat label.

  8. Aroesty JM, Kannam JP. Patient education: medications for angina (beyond the basics). UpToDate.

  9. Gulati M, Levy PD, Mukherjee D, et al. 2021 AHA/ACC/ASE/CHEST/SAEM/SCCT/SCMR Guideline for the Evaluation and Diagnosis of Chest Pain: Executive summary: a report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2021;144(22):e368-e454. doi:10.1161/CIR.0000000000001029.