How does this medication work? What will it do for me?

Isosorbide-5-mononitrate belongs to the family of medications known as anti-anginals. This medication is used to prevent angina attacks associated with coronary artery disease. It is not useful for the quick relief of an attack.

It acts by opening up the blood vessels that supply the heart, increasing the blood and oxygen supply to the heart. Isosorbide-5-mononitrate may reduce the number, length, and severity of angina attacks. Tolerance to exercise may be increased and the need for fast-acting nitroglycerin (tablets and spray) may be reduced.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each oval, yellow, biconvex, film-coated, extended release tablet, scored on both sides and engraved "A" over "ID" on one side, contains isosorbide-5-mononitrate 60 mg. Nonmedicinal ingredients: tablet core: colloidal silicon dioxide, hydroxypropyl cellulose, magnesium stearate, paraffin, and sodium aluminum silicate; coating: hydroxypropyl methylcellulose, iron oxide yellow, paraffin, polyethylene glycol, and titanium dioxide.

How should I use this medication?

The recommended adult dose of isosorbide-5-mononitrate is 1 tablet (60 mg) taken once daily in the morning after getting up. Your doctor may increase the dose to 2 tablets (120 mg) once daily in the morning if necessary. To reduce the risk of headache, your doctor may suggest starting with one-half tablet (30 mg) once daily each morning for the first 2 to 4 days.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

The tablets should not be chewed or crushed, and should be swallowed together with half a glass of water. If necessary, the tablet may be split in half and the half tablet may be swallowed whole. You may sometimes find whole tablets in the stool. These are only the shell of the tablet, and you can be sure that the medication has been released.

The tablets are available in a 30-day package that is designed to make it easy to keep track of your medication. 28 tablets are labeled with a day of the week. To start, take a tablet in the first row that matches the day you begin this pack. Then take a tablet on each of the following days to complete the 28 labelled tablets. The 2 extra non-labelled tablets should be taken after all the other tablets are gone.

It is important to take this medication exactly as prescribed by your doctor. Isosorbide-5-mononitrate should be taken at about the same time every day. If you miss a dose and remember within 6 hours, take your usual dose as soon as possible, then go back to your regular schedule. If it has been more than 6 hours when you remember, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to isosorbide-5-mononitrate or any ingredients of this medication
  • are allergic to other nitrates or nitrites
  • are in a state of acute circulatory failure associated with extremely low blood pressure (e.g., states of shock or collapse)
  • are taking sildenafil, tadalafil, or vardenafil
  • experience dizziness, blurred vision, or loss of consciousness when rising from a sitting or lying position
  • have increased pressure inside the head
  • have myocardial insufficiency due to obstruction
  • have severe anemia

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal pain
  • constipation
  • diarrhea
  • dizziness or lightheadedness, especially when rising from a lying or sitting position
  • flushing of face and neck
  • gas
  • headache
  • increased sweating
  • nausea
  • restlessness
  • sensation of spinning
  • trouble sleeping

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • blurred vision
  • chest pain (angina pain)
  • cough
  • heartburn
  • rapid or pounding heartbeat
  • severe or prolonged headache

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a heart attack (e.g., chest pain or pressure, pain extending through shoulder and arm, nausea and vomiting, sweating)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Drowsiness/reduced alertness: This medication may cause faintness or dizziness. Do not drive, operate machinery, or perform other potentially hazardous tasks until you have determined how this medication affects you.

Heart disease: Isosorbide-5-mononitrate may cause some symptoms of heart disease to become worse. If you have heart problems caused by not enough oxygen being available for the heart or other organs of the body, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Low blood pressure: Symptoms of severe lowering of blood pressure, such as weakness or dizziness, particularly when rising suddenly from a sitting or lying position, may occur. People who are prone to low blood pressure (e.g., those taking diuretics) should be cautious when using this medication.

Tolerance: With continued use, isosorbide-5-mononitrate may stop having beneficial effects because the body gets used to it (i.e., develops a tolerance). Call your doctor if at any time you feel that your angina attacks are getting worse or happening more often.

Withdrawal: Stopping this medication suddenly may occasionally aggravate chest pain or other symptoms of angina. To avoid possible withdrawal effects, this medication should be gradually reduced and not stopped suddenly. Do not change the way you are taking this medication without speaking to your doctor.

Pregnancy: Studies demonstrating the safety and effectiveness of using isosorbide-5-mononitrate during pregnancy are not available. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if isosorbide-5-mononitrate passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children. Its use by this age group is not recommended.

Seniors: Seniors may be more likely to experience dizziness or lightheadedness while taking this medication.

What other drugs could interact with this medication?

There may be an interaction between isosorbide-5-mononitrate and any of the following:

  • alcohol
  • angiotensin converting enzyme (ACE) inhibitors (e.g., captopril, lisinopril, ramipril)
  • atypical antipsychotics (e.g., quetiapine, risperidone)
  • "azole" antifungal agents (e.g., itraconazole, ketoconazole, voriconazole)
  • benzodiazepines (e.g., alprazolam, diazepam, midazolam, triazolam)
  • beta-blockers (e.g., carvedilol, propranolol, timolol)
  • calcium channel blockers (e.g., amlodipine, diltiazem, verapamil, nifedipine)
  • delaviridine
  • diuretics (water pills; e.g., furosemide, hydrochlorothiazide, spironolactone)
  • ergot alkaloids
  • isoniazid
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • other medications that reduce blood pressure
  • phosphodiesterase-5 inhibitors (e.g., sildenafil, taladafil, vardenafil)
  • protease inhibitors (e.g., amprenavir, atazanavir, fosamprenavir, indinavir, ritonavir, saquinavir)
  • rosiglitazone
  • tricyclic antidepressants (e.g., amitriptyline, desipramine)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.