Isosorbide Mononitrate 20mg Tabs
It is used to prevent or treat chest pain (angina pectoris) in people with heart disease. Do not use this drug to treat sudden chest pain. It will not help. Talk with your doctor.
Drug Class
Antianginal
Pharmacologic Class
Organic Nitrate; Vasodilator
Pregnancy Category
Category C
FDA Approved
Mar 1991
DEA Schedule
Not Controlled
Overview
What is this medicine?
Isosorbide mononitrate is a medication used to prevent chest pain (angina) caused by heart disease. It works by relaxing blood vessels, which helps more blood and oxygen reach your heart, and reduces the heart's workload.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, it's essential to use it exactly as directed by your doctor. Carefully read all the information provided with your medication and follow the instructions closely. If you need to stop taking this medication, do not stop suddenly without first consulting your doctor, as this may increase your risk of side effects. Instead, your doctor will advise you on how to gradually taper off the medication.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless specifically instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also want to explore local drug take-back programs for a safe and environmentally responsible disposal option.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To get the most benefit from your medication, it's essential to use it exactly as directed by your doctor. Carefully read all the information provided with your medication and follow the instructions closely. If you need to stop taking this medication, do not stop suddenly without first consulting your doctor, as this may increase your risk of side effects. Instead, your doctor will advise you on how to gradually taper off the medication.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless specifically instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also want to explore local drug take-back programs for a safe and environmentally responsible disposal option.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take this medication exactly as prescribed, usually twice a day with a 7-hour gap between doses to prevent tolerance.
- Do not crush, chew, or break extended-release tablets (if applicable).
- Avoid sudden changes in position (e.g., standing up quickly) to prevent dizziness or fainting.
- Avoid alcohol, as it can increase dizziness and lower blood pressure.
- Avoid hot baths, showers, or saunas, as these can also lower blood pressure.
- This medication is for preventing angina, not for treating an acute angina attack. For acute attacks, use sublingual nitroglycerin as prescribed.
- Report any new or worsening symptoms to your doctor.
Available Forms & Alternatives
Available Strengths:
- Isosorbide Dinitrate 30mg Oral Tabs
- Isosorbide Dinitrate 5mg Oral Tabs
- Isosorbide Dinitrate 20mg Tablets
- Isosorbide Dinitrate 10mg Oral Tabs
- Isosorbide Mononitrate 10mg Tabs
- Isosorbide Mononitrate 120mg ER Tab
- Isosorbide Mononitrate 30mg ER Tabs
- Isosorbide Mononitrate 60mg ER Tabs
- Isosorbide Mononitrate 60mg ER Tabs
- Isosorbide Dinitrate 40mg Tablets
- Isosorbide Mononitrate 30mg ER Tabs
- Isosorbide Mononitrate 120mg ER Tab
- Isosorbide Mononitrate 20mg Tabs
- Isosorbide Mononitrate 20mg Tabs
- Isosorbide Mononitrate 10mg Tabs
Dosing & Administration
Adult Dosing
Standard Dose:
20 mg twice daily, with the two doses given 7 hours apart (e.g., 8 AM and 3 PM) to provide a nitrate-free interval to prevent tolerance.
Dose Range:
20 - 40 mg
Condition-Specific Dosing:
anginaProphylaxis:
20 mg twice daily, with doses separated by 7 hours. May be increased to 40 mg twice daily if needed, maintaining the 7-hour separation.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No specific dose adjustment generally required.
Moderate:
No specific dose adjustment generally required, but use with caution.
Severe:
No specific dose adjustment generally required, but use with caution and monitor for adverse effects.
Dialysis:
Not significantly removed by dialysis; no specific dose adjustment needed, but monitor for adverse effects.
Hepatic Impairment:
Mild:
No specific dose adjustment generally required.
Moderate:
No specific dose adjustment generally required, but use with caution.
Severe:
No specific dose adjustment generally required, but use with caution and monitor for adverse effects.
Pharmacology
Mechanism of Action
Isosorbide mononitrate is an organic nitrate that acts as a vasodilator. It is metabolized to nitric oxide (NO), which activates guanylate cyclase, leading to an increase in cyclic guanosine monophosphate (cGMP) in vascular smooth muscle. This results in dephosphorylation of myosin light chains and relaxation of smooth muscle. The primary effect is venodilation, which reduces preload and myocardial oxygen demand. It also causes arterial dilation, reducing afterload and improving coronary blood flow.
Pharmacokinetics
Absorption:
Bioavailability:
100%
Tmax:
30-60 minutes (immediate-release)
FoodEffect:
Food does not significantly affect absorption.
Distribution:
Vd:
0.6 L/kg
ProteinBinding:
<5%
CnssPenetration:
Limited
Elimination:
HalfLife:
Approximately 5 hours
Clearance:
Not available
ExcretionRoute:
Renal (primarily as glucuronide conjugates and denitrated metabolites)
Unchanged:
<2% (in urine)
Pharmacodynamics
OnsetOfAction:
Within 20 minutes
PeakEffect:
30-60 minutes
DurationOfAction:
Approximately 7 hours (immediate-release)
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Abnormal heartbeat (fast or slow)
New or worsening chest pain
Other Possible Side Effects
Like all medications, this drug can cause side effects. Although many people do not experience any side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Dizziness
Headaches (common when starting the medication, but often improves over time; do not adjust your dosage without consulting your doctor)
* Other side effects not listed here
If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Abnormal heartbeat (fast or slow)
New or worsening chest pain
Other Possible Side Effects
Like all medications, this drug can cause side effects. Although many people do not experience any side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or do not go away, contact your doctor:
Dizziness
Headaches (common when starting the medication, but often improves over time; do not adjust your dosage without consulting your doctor)
* Other side effects not listed here
If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe or persistent headache
- Dizziness or lightheadedness that does not go away
- Fainting spells
- Blurred vision
- Unusual weakness or fatigue
- Chest pain that worsens or does not improve
- Rash or itching
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
A history of heart failure, which is a condition where the heart is not pumping blood as well as it should.
If you have recently had a heart attack.
If you are currently taking any of the following medications: Avanafil, riociguat, sildenafil, tadalafil, or vardenafil.
Please note that this is not an exhaustive list of all potential interactions with this medication. Therefore, it is crucial to discuss all of your medications, including prescription and over-the-counter drugs, natural products, and vitamins, with your doctor and pharmacist. This will help ensure that it is safe for you to take this medication in conjunction with your other medications and health conditions.
Remember, do not start, stop, or change the dose of any medication without first consulting your doctor to confirm that it is safe to do so.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
A history of heart failure, which is a condition where the heart is not pumping blood as well as it should.
If you have recently had a heart attack.
If you are currently taking any of the following medications: Avanafil, riociguat, sildenafil, tadalafil, or vardenafil.
Please note that this is not an exhaustive list of all potential interactions with this medication. Therefore, it is crucial to discuss all of your medications, including prescription and over-the-counter drugs, natural products, and vitamins, with your doctor and pharmacist. This will help ensure that it is safe for you to take this medication in conjunction with your other medications and health conditions.
Remember, do not start, stop, or change the dose of any medication without first consulting your doctor to confirm that it is safe to do so.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
When starting this medication, avoid driving and other activities that require alertness until you understand how it affects you. To minimize the risk of dizziness or fainting, get up slowly from a sitting or lying down position, and be cautious when climbing stairs.
Follow your healthcare provider's instructions for monitoring your blood pressure. Additionally, be aware that this medication may interfere with certain laboratory tests, so inform all your healthcare providers and laboratory personnel that you are taking this drug.
Before consuming alcohol, discuss the potential risks with your doctor. If you experience new or worsening chest pain or pressure, seek emergency medical attention immediately.
Long-term, uninterrupted use of this medication can lead to reduced effectiveness, a phenomenon known as tolerance. To avoid this, ensure you have a daily "nitrate-free" period. If you notice the medication is not working as well as it previously did, consult your doctor. Do not exceed the prescribed dosage.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential benefits and risks with your doctor to make an informed decision about using this medication.
When starting this medication, avoid driving and other activities that require alertness until you understand how it affects you. To minimize the risk of dizziness or fainting, get up slowly from a sitting or lying down position, and be cautious when climbing stairs.
Follow your healthcare provider's instructions for monitoring your blood pressure. Additionally, be aware that this medication may interfere with certain laboratory tests, so inform all your healthcare providers and laboratory personnel that you are taking this drug.
Before consuming alcohol, discuss the potential risks with your doctor. If you experience new or worsening chest pain or pressure, seek emergency medical attention immediately.
Long-term, uninterrupted use of this medication can lead to reduced effectiveness, a phenomenon known as tolerance. To avoid this, ensure you have a daily "nitrate-free" period. If you notice the medication is not working as well as it previously did, consult your doctor. Do not exceed the prescribed dosage.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, discuss the potential benefits and risks with your doctor to make an informed decision about using this medication.
Overdose Information
Overdose Symptoms:
- Severe hypotension (low blood pressure)
- Persistent throbbing headache
- Palpitations
- Flushing
- Dizziness
- Nausea and vomiting
- Diaphoresis (sweating)
- Syncope (fainting)
- Tachycardia (fast heart rate)
- Methemoglobinemia (rare, but serious, characterized by cyanosis, dyspnea, confusion, seizures)
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Management includes supportive care, fluid administration for hypotension, and potentially methylene blue for severe methemoglobinemia.
Drug Interactions
Contraindicated Interactions
- Phosphodiesterase-5 (PDE5) inhibitors (e.g., sildenafil, tadalafil, vardenafil, avanafil) - concurrent use can cause severe hypotension and cardiovascular collapse.
- Riociguat (soluble guanylate cyclase stimulator) - concurrent use can cause severe hypotension.
Major Interactions
- Other vasodilators (e.g., alpha-blockers, calcium channel blockers) - additive hypotensive effects.
- Alcohol - additive hypotensive effects.
Moderate Interactions
- Antihypertensives - may potentiate hypotensive effects.
- Tricyclic antidepressants - may reduce hypotensive effects of nitrates (rare).
Monitoring
Baseline Monitoring
Blood Pressure (BP)
Rationale: To establish baseline and identify potential for hypotension.
Timing: Prior to initiation of therapy.
Heart Rate (HR)
Rationale: To establish baseline and identify potential for reflex tachycardia.
Timing: Prior to initiation of therapy.
Routine Monitoring
Blood Pressure (BP)
Frequency: Regularly, especially during dose titration and if symptoms of hypotension occur.
Target: Maintain within patient's normal range, avoiding symptomatic hypotension.
Action Threshold: Systolic BP <90 mmHg or symptomatic hypotension (dizziness, syncope).
Heart Rate (HR)
Frequency: Regularly, especially during dose titration.
Target: Maintain within patient's normal range.
Action Threshold: Significant reflex tachycardia (>100 bpm or symptomatic).
Angina Symptoms (frequency, severity, duration)
Frequency: Continuously by patient report.
Target: Reduction in angina episodes.
Action Threshold: Increased frequency or severity of angina, indicating inadequate control or tolerance development.
Symptom Monitoring
- Headache (common, often transient)
- Dizziness
- Lightheadedness
- Flushing
- Nausea
- Hypotension (especially orthostatic)
- Syncope
- Palpitations
- Blurred vision
Special Patient Groups
Pregnancy
Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects at high doses, but there are no adequate and well-controlled studies in pregnant women.
Trimester-Specific Risks:
First Trimester:
Potential for fetal harm, but human data are limited.
Second Trimester:
Potential for fetal harm, but human data are limited.
Third Trimester:
Potential for fetal harm, but human data are limited.
Lactation
It is not known whether isosorbide mononitrate is excreted in human milk. Caution should be exercised when administered to a nursing woman.
Infant Risk:
Unknown; potential for adverse effects on the infant. Monitor for hypotension, headache, or other signs of nitrate exposure.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Use is generally not recommended.
Geriatric Use
Elderly patients may be more susceptible to the hypotensive effects of nitrates. Initiate therapy with caution and monitor blood pressure closely. Dosage adjustments may be necessary based on individual response and tolerability.
Clinical Information
Clinical Pearls
- Isosorbide mononitrate is used for prophylaxis of angina, not for acute attacks. Patients should carry sublingual nitroglycerin for acute relief.
- To prevent nitrate tolerance, a nitrate-free interval (typically 7-14 hours) is crucial. For immediate-release tablets, this is achieved by spacing the two daily doses about 7 hours apart.
- Headache is a very common side effect, especially at the beginning of therapy. It often diminishes with continued use and can be managed with mild analgesics.
- Patients should be advised about orthostatic hypotension and to rise slowly from a sitting or lying position.
- Concomitant use with PDE5 inhibitors (e.g., sildenafil, tadalafil) is absolutely contraindicated due to the risk of severe, life-threatening hypotension.
Alternative Therapies
- Beta-blockers (e.g., metoprolol, atenolol)
- Calcium channel blockers (e.g., amlodipine, diltiazem, verapamil)
- Ranolazine
- Isosorbide dinitrate (requires more complex dosing to avoid tolerance)
Cost & Coverage
Average Cost:
$10 - $50 per 30 tablets (20mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (preferred generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.