Isosorbide Mononitrate and Isosorbide Dinitrate

What are isosorbide mononitrate and isosorbide dinitrate?

These are prescription-only nitrate medications used to manage and prevent the symptoms of angina (chest pain) and to help manage heart failure. They work by relaxing and widening blood vessels, which reduces the workload on the heart and improves oxygen delivery to the heart muscle[1]: 

• Isosorbide mononitrate is typically used in tablet form, including standard and modified-release preparations 

• Isosorbide dinitrate is available in tablets and intravenous infusions, mainly used in hospital settings 

What are isosorbide mononitrate and isosorbide dinitrate used for?

These medicines are prescribed for several heart-related conditions[1]: 

• Stable angina (to prevent chest pain episodes) 

• Heart failure (as an add-on treatment) 

• Post-heart attack care in some cases 

They are not used to relieve sudden angina attacks – short-acting nitrates like glyceryl trinitrate (GTN) are used for that purpose [3]. 

How do isosorbide mononitrate and isosorbide dinitrate work?

Isosorbide mononitrate and dinitrate act as vasodilators. This means they[1]: 

• Relax and widen blood vessels 

• Reduce the effort needed for the heart to pump 

• Increase blood flow and oxygen supply to the heart muscle 

• Improve circulation in heart failure, helping the heart work more efficiently [3] 

Who can take isosorbide mononitrate and isosorbide dinitrate?

These medicines are suitable for most adults with angina or heart failure. However, they are not appropriate for everyone. They may not be not suitable for[1]: 

• People with very low blood pressure 

• Individuals with recent head trauma or brain bleeding 

• People with an underactive thyroid 

• People who have had a stroke 

• People with anaemia or glaucoma 

• People taking erectile dysfunction drugs (e.g. sildenafil) 

• Those allergic to nitrates 

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

How do you take isosorbide mononitrate and isosorbide dinitrate?

These medicines must be taken exactly as prescribed[1]: 

• Swallow tablets whole with water 

• Take at the same time each day 

• Do not chew or crush modified-release tablets 

• Follow medical instructions carefully, particularly when they tell you to leave a particular gap of time between your doses

What is the typical dosage of isosorbide mononitrate and isosorbide dinitrate?

The dosage depends on the formulation, condition, and patient tolerance. 

For angina[1]:  

• Isosorbide mononitrate: 

• Standard tablets: 10mg, twice daily, up to a maximum of 120mg a day split into smaller doses 

• Modified-release tablets or capsules: 25mg to 60mg, once daily, up to a maximum dose of 120mg  

• Isosorbide dinitrate: 

• Standard tablets: 30mg to 120mg,daily in divided doses 

• Modified-release tablets or capsules: 40mg taken once a day or in divided doses, up to a maximum dose of 80mg taken over two to three divided doses 

For heart failure[1]:  

• Isosorbide mononitrate: 

• Standard tablets: 10mg to 20mg, two to three times daily, or 40mg twice a day, up to a maximum of 120mg a day split into smaller doses 

• Isosorbide dinitrate: 

• Standard tablets: 40mg to 160mg, twice daily, up to a maximum dose of 240mg a day split into smaller doses 

Can you stop taking isosorbide mononitrate and isosorbide dinitrate?

No – stopping suddenly may cause chest pain to return or heart failure to worsen. Always speak to your doctor or pharmacist before discontinuing[1]. 

What do you do if you take too much isosorbide mononitrate and isosorbide dinitrate?

Taking too much can lead to serious side effects, including[1]: 

• Severe dizziness 

• Fainting 

• Rapid heartbeat 

• Nausea 

Seek emergency medical attention if this happens.

What do you do if you forget to take isosorbide mononitrate and isosorbide dinitrate?

If you miss a dose[1]: 

• Take it when you remember 

• If it’s nearly time for your next dose, skip the missed one 

• Do not take two doses together 

How do you store isosorbide mononitrate and isosorbide dinitrate?

To ensure safety and effectiveness[1]: 

• Store below 25°C 

• Keep in the original packaging 

• Keep out of reach of children 

• Do not use past the expiry date 

What medicines can you not take with isosorbide mononitrate and isosorbide dinitrate?

Certain medicines and substances may interact with nitrates and should be avoided unless advised otherwise[1]: 

• Erectile dysfunction drugs (sildenafil, tadalafil, vardenafil) 

• Other medications that lower blood pressure 

• Medications for high blood pressure or heart problems 

• Alcohol (can increase dizziness or fainting) 

• Medications for depression or other mental health conditions 

• Medications for migraine that contain ergotamine 

• Riociguat (for pulmonary hypertension) 

• Sapropterin, a medicine for phenylketonuria 

• General anaesthetics (inform your surgeon if you're taking nitrates) 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of isosorbide mononitrate and isosorbide dinitrate?

Most people tolerate these medicines well, but side effects can occur. Common side effects include[1]: 

• Headache (often settles with continued use) 

• Dizziness or tiredness 

• Flushing 

• Nausea  

Rare but serious side effects include[1]: 

• Heart beating faster or slower than normal 

• Severe eye pain, blurred vision or sudden loss of eyesight as a sign of acute angle closure glaucoma 

• Chest pain in people diagnosed with angina 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include[1]:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

 If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about isosorbide mononitrate and isosorbide dinitrate

How quickly do they work? 
Usually within one hour[1]. 

Can I take them long-term? 
Yes – they’re often prescribed for ongoing use[1]. 

Can I drink alcohol? 
Limit alcohol, as it can enhance side effects like dizziness[1]. 

Can I take them with food? 
Yes but be consistent with timing[1]. 

Do they affect sex life? 
They don’t directly but should not be used with erectile dysfunction medication[1]. 

Do I need to stop before surgery? 
Possibly – discuss this with your doctor or anaesthetis[1]t. 

Can I exercise? 
Yes, build up gradually and carry GTN spray if prescribed[1]. 

Do they affect contraception? 
No, but combined oral contraceptives may not be recommended for people with angina[1]. 

What if I still get chest pain? 
You should use your GTN spray or tablets as needed and contact your doctor[1]. 

For the official NHS guide to isosorbide mononitrate and isosorbide dinitrate, visit their website.