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Isosorbide mononitrate

Brand names: Imdur, Monoket

Isosorbide mononitrate is a long-acting nitrate taken every day to help prevent chest pain from angina.

Brand namesImdur, Monoket
Type of medicineNitrate (angina medicine)
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It doesn't stop an attack that's happening. Use nitroglycerin for that.

What it's used for

  • Preventing angina

How to take it

  • Take extended-release tablets once in the morning. Swallow them whole (some can be split; check your label).
  • The schedule leaves a nitrate-free period so it keeps working; don't add extra doses.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Headache (often eases in a week or two)
  • Dizziness
  • Flushing
Call 911Chest pain that's new, worse, or doesn't go away with nitroglycerin
Call 911Fainting

Warnings

  • Don't stop suddenly; angina can get worse.
  • Stand up slowly.

Other medicines, foods, and alcohol

  • Never take with erectile dysfunction medicines (sildenafil, tadalafil, vardenafil) or riociguat; blood pressure can drop dangerously.
  • Alcohol adds to dizziness.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Talk with your provider.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.