What is isosorbide mononitrate?

Isosorbide mononitrate is in a class of drugs called nitrates. Isosorbide mononitrate dilates (widens or relaxes) blood vessels (arteries and veins). When blood vessels are dilated, it is easier for the heart to pump. Also, more blood, which is rich in oxygen, can flow to the heart.

Isosorbide is used to prevent angina attacks (chest pain).

Isosorbide mononitrate may also be used for purposes other than those listed in this medication guide.


Before taking this medication, tell your doctor if you

  • have had a heart attack
  • have congestive heart failure
  • have low blood pressure;
  • have had a stroke, a transient ischemic attack (TIA, or mini-stroke), or a serious head injury;
  • have anemia;
  • have an allergy to nitrates;
  • have closed-angle glaucoma;
  • suffer from migraines;
  • have kidney disease; or
  • have liver disease.

The conditions listed above may prevent you from taking isosorbide or you may need a dosage adjustment or special monitoring during your therapy.

Isosorbide mononitrate is in the FDA pregnancy category C. This means that it is not known whether it will harm an unborn baby. Do not take isosorbide mononitrate without first talking to your doctor if you are pregnant.

It is also not known whether isosorbide passes into breast milk. Do not take isosorbide mononitrate without first talking to your doctor if you are breast-feeding a baby.

Use caution when driving, operating machinery, or performing other hazardous activities. Also, stand up slowly from a sitting or lying position. Isosorbide mononitrate may cause dizziness. If you experience dizziness, avoid hazardous activities.

Avoid alcohol. It also widens your blood vessels and it can cause very low blood pressure, dizziness and drowsiness and you could endanger yourself or others.

Do not stop taking isosorbide mononitrate suddenly.

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Seek emergency medical attention.

Symptoms of an isosorbide mononitrate overdose include a severe throbbing headache, difficult or slow breathing, muscle cramps, nausea, vomiting, diarrhea, fever, dizziness, fainting, an irregular heartbeat, changes in vision, flushing, and seizures.

Take the missed dose as soon as you remember. If you are taking the regular tablets (not the extended-release tablets) and your next regularly scheduled dose is within 2 hours, skip the dose you missed and take only your next regularly scheduled dose. If you are taking the extended release tablets and your next regularly scheduled dose is within 6 hours, also skip the missed dose and take only your next regularly scheduled dose. Do not take a double dose of this medication.

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Side effects

If you experience any of the following serious side effects, stop taking isosorbide mononitrate and seek emergency medical attention:

  • an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
  • blurred vision or dry mouth; or
  • irregular heartbeat;
  • fainting.

Other, less serious side effects may be more likely to occur. Continue to take isosorbide and talk to your doctor if you experience

  • headache or dizziness,
  • flushing (redness of the face, neck, and chest),
  • nausea or vomiting,
  • a fast heartbeat,
  • swollen ankles, or
  • weakness.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects to FDA at 1-800-FDA-1088.

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Do not use sildenafil (Viagra), a drug used to treat impotence, while taking isosorbide mononitrate. The combination could cause severe or life-threatening low blood pressure.

Before taking isosorbide mononitrate, tell your doctor if you are taking any of the following medicines:

  • dihydroergotamine (D.H.E. 45); or
  • any other heart medicines, especially those used to treat high blood pressure or irregular heartbeats.

You may require a dosage adjustment or special monitoring during your treatment if you are taking any of the medicines listed above.

Do not drink alcohol. Like isosorbide mononitrate, alcohol widens your blood vessels, and it can cause very low blood pressure, dizziness, and drowsiness. If you combine isosorbide mononitrate and alcohol, you could endanger yourself or others.

Drugs other than those listed here may also interact with isosorbide mononitrate or affect your condition. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines.

Other Names

ISMO, Imdur, Monoket, and isosorbide mononitrate

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Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2004 Cerner Multum, Inc. Version 2.05. Revision date 8/23/04

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