Last updated on RxList: 2/24/2021
Ismo Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

What Is Ismo?

Ismo (isosorbide mononitrate) is a nitrate vasodilator used to treat angina, but not used to treat acute angina. Ismo is available as a generic with several names, but isosorbide mononitrate is the generic term.

What Are Side Effects of Ismo?

Common side effects of Ismo include:

  • headache,
  • dizziness,
  • skin warmth or redness,
  • tingling under your skin,
  • nausea,
  • vomiting,
  • constipation,
  • hot flashes,
  • dry mouth,
  • diarrhea, or
  • pain or stiffness in joints or muscles.

Serious side effects of Ismo include:

Dosage for Ismo

Ismo (isosorbide mononitrate) is available in strength of 20 mg tablets. Dosage is usually 20mg twice a day, about 7 hours apart.

What Drugs, Substances, or Supplements Interact with Ismo?

Ismo may interact with dihydroergotamine or ergotamine, erectile dysfunction medications, beta-blockers, or heart or blood pressure medicines. Tell your doctor all medications and supplements you use.

Ismo During Pregnancy and Breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant while using Ismo; it is unknown if Ismo will harm a fetus. It is unknown if Ismo passes into breast milk or if it could harm a nursing baby. Consult your doctor before breastfeeding.

Additional Information

Our Ismo Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Ismo Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • a light-headed feeling, like you might pass out;
  • worsening angina pain;
  • fast or slow heart rate; or
  • pounding heartbeats or fluttering in your chest.

Isosorbide mononitrate can cause severe headaches. These headaches may gradually become less severe as you continue to use nitroglycerin. Do not stop taking this medicine to avoid headaches. Ask your doctor before using any headache pain medication.

Common side effects may include:

  • headache; or
  • flushing (warmth, redness, or tingly feeling).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Ismo (Isosorbide Mononitrate)


Heart Disease: Symptoms, Signs, and Causes See Slideshow
Ismo Professional Information


The table below shows the frequencies of the adverse reactions observed in more than 1% of the subjects (a) in 6 placebo-controlled domestic studies in which patients in the active-treatment arm received 20 mg of isosorbide mononitrate twice daily, and (b) in all studies in which patients received isosorbide mononitrate in a variety of regimens. In parentheses, the same table shows the frequencies with which these adverse reactions led to discontinuation of treatment. Overall, 11% of the patients who received isosorbide mononitrate in the six controlled U.S. studies discontinued treatment because of adverse reactions. Most of these discontinued because of headache. "Dizziness" and nausea were also frequently associated with withdrawal from these studies.

Frequency of Adverse Reactions (Discontinuations)*
  6 Controlled Studies 92 Clinical Studies
Dose Placebo 20 mg (varied)
Patients 204 219 3344
Headache 9% (0%) 38% (9%) 19% (4.3%)
Dizziness 1% (0%) 5% (1%) 3% (0.2%)
Nausea, Vomiting < 1% (0%) 4% (3%) 2% (0.2%)
*Some individuals discontinued for multiple reasons.

Other adverse reactions, each reported by fewer than 1% of exposed patients, and in many cases of uncertain relation to drug treatment, were::

Cardiovascular: angina pectoris, arrhythmias, atrial fibrillation, hypotension, palpitations, postural hypotension, premature ventricular contractions, supraventricular tachycardia, syncope.

Dermatologic: pruritus, rash.

Gastrointestinal: abdominal pain, diarrhea, dyspepsia, tenesmus, tooth disorder, vomiting.

Genitourinary: dysuria, impotence, urinary frequency.

Miscellaneous: asthenia, blurred vision, cold sweat, diplopia, edema, malaise, neck stiffness, rigors.

Musculoskeletal: arthralgia.

Neurological: agitation, anxiey, confusion, dyscoordination, hypoesthesia, hypokinesia, increased appetite, insomnia, nervousness, nightmares.

Respiratory: bronchitis, pneumonia, upper-respiratory tract infection.

Extremely rarely, ordinary doses of organic nitrates have caused methemoglobinemia in normal-seeming patients; for futher discussion of its diagnosis and treatment see under OVERDOSAGE.

Read the entire FDA prescribing information for Ismo (Isosorbide Mononitrate)


In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer

© Ismo Patient Information is supplied by Cerner Multum, Inc. and Ismo Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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