Pharmacy Guide
Patient leaflets and SmPCs, drug interaction checker, official dosages and NHS pharmacy opening hours — all in one place.
Pharmacy Guide
Patient leaflets and SmPCs, drug interaction checker, official dosages and NHS pharmacy opening hours — all in one place.
Isodur 25XL Capsules
⚠ This medicine appears to have been discontinued
The electronic medicines compendium (emc) no longer publishes a Summary of Product Characteristics for this product, which usually means it is no longer marketed in the UK. The patient leaflet below is kept for reference, but the product may not be available.
If you were prescribed this medicine, other products containing Isosorbide mononitrate may still be available. Do not stop your treatment — ask your pharmacist or GP what to use instead.
What it is and what it is used for
for
Isodur Capsules are one of a group of medicines known as nitrates. Nitrates work by widening the blood vessels in your heart to allow an increased amount of blood flow to areas which need it. They are used to help prevent an attack of angina (chest pain). This pain comes from the heart muscle and is a sign that part of it is not getting enough oxygen for the amount of work it is doing. Isodur capsules are not suitable for the relief of an angina attack.
2.
What you need to know before you take it
e Isodur Capsules
Do not take Isodur Capsules:
- if you are allergic to isosorbide-5-mononitrate, other nitrates or any of the other ingredients of this medicine (listed in section 6)
- if you are suffering a heart attack or have recently had a heart attack
- if you have been diagnosed with any of the following heart conditions: hypertrophic obstructive cardiomyopathy (HOCM), constrictive pericarditis, cardiac tamponade, low cardiac filling pressures, aortic/mitral valve stenosis
- if your blood has stopped circulating around your body properly (circulatory failure)
- if you are suffering from "shock" or vascular collapse
- if you suffer from severe anaemia (severe reduction in red blood cells)
- if you have been diagnosed with any diseases associated with raised intracranial (head) pressure
- if you are suffering from or have had a head injury (trauma)
- if you are suffering from or have had bleeding in the brain (brain haemorrhage)
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if you have an eye disease called glaucoma if you suffer from very low blood pressure (severe hypotension) if you suffer from low circulating blood volume (hypovolaemia) if you take sildenafil ("Viagra") or any similar medicines used to treat erectile dysfunction (known as phosphodiesterase type-5 inhibitors) if you take products that contain riociguat, a medicine used in treating pulmonary hypertension
If any of the above applies to you talk to your doctor or pharmacist. Warnings and precautions Talk to your doctor, pharmacist or nurse before taking Isodur Capsules
- if you are pregnant or there is a chance you might become pregnant
- if you are breast-feeding
- if you suffer from liver problems
- if you suffer from kidney problems
- if you are at risk of developing, or have a family history of, glaucoma
- if you suffer from an under-active thyroid gland (a condition known as hypothyroidism)
- if you suffer from hypothermia (very low body temperature)
- if you suffer from malnutrition (severe lack of food)
- if you suffer from very poor circulation
- if you have slower than normal bowel movements If any of the above apply to you, it is important that you tell your doctor or pharmacist before taking Isodur and they will decide what to do. It may still be safe for you to take Isodur. Children Isodur Capsules should not be taken by children. Other medicines and Isodur Capsules Do not take Viagra (sildenafil – for male erectile dysfunction) or other phosphodiesterase type-5 inhibitors while you are taking Isodur. Taking these medicines while you are taking Isodur could cause a severe and possibly dangerous fall in blood pressure. This could result in collapse, unconsciousness and could be fatal. You must not stop taking Isodur to take these medicines as this will increase your chances of having an angina attack. Do not take Isodur with products that contain riociguat, a medicine used in treating pulmonary hypertension. It is important that you inform your doctor or pharmacist if you are taking any of the following medicines:
- Medicines that can lower your blood pressure
- Tricyclic antidepressants (used to treat depression) and neuroleptics (used to treat anxiety)
- Ergotamine used for migraine
- Sapropterin used for phenylketonuria (PKU) Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines, including medicines obtained without a prescription.
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Isodur Capsules with alcohol Do not drink alcohol while taking Isodur Capsules. Alcohol could increase the effect of Isodur and lower your blood pressure too much. If this happens, you may feel dizzy or faint. Pregnancy and breast-feeding If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine. You should not use Isodur Capsules during pregnancy or while breast-feeding unless your doctor thinks it is essential. Driving and using machines Isodur Capsules may give you a headache, blurred vision or make you feel faint, dizzy or tired. If this happens to you, do not drive or operate machinery. Isodur Capsules contain Sucrose If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product. Isodur Capsules contain Sodium This medicine contains less than 1 mmol sodium (23 mg) per dosage unit, that is to say essentially 'sodium-free'.
3.
How to take it
Isodur Capsules
If this product has been prescribed by your doctor the label on the carton will tell you how many capsules you should take and when. Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure. The recommended dose is one or two capsules to be taken in the morning. This product should be taken orally (by mouth). You must swallow the capsules whole with a drink of water. The capsules must not be crushed or chewed. Elderly patients or patients with low blood pressure, kidney or liver disease may be advised to take a lower dose. Do not use Isodur to treat an actual angina attack. Your doctor will give you a different medicine such as GTN (glyceryl trinitrate) spray or tablet for this. Use in children This medicine should not be given to children. If you take more Isodur Capsules than you should If you take too many capsules, contact your nearest hospital casualty department or doctor immediately. Take this leaflet and any remaining capsules with you. Too much Isodur may cause your blood pressure to fall too low, making you feel sick, faint and dizzy. A very large overdose could cause a coma or collapse and require immediate resuscitation.
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If you forget to take Isodur Capsules If you forget to take your capsule(s), take your recommended dose as soon as you remember and then carry on as normal. Do not take a double dose to make up for a forgotten dose. If you stop taking Isodur Capsules Do not stop taking Isodur Capsules without consulting your doctor. Stopping your medicine suddenly may lead to your condition getting worse. If you have an angina attack (chest pain) despite taking Isodur Capsules, your doctor will supply you with another medicine for this. Do not stop taking your Isodur Capsules. If you have any further questions on the use of this medicine, ask your doctor, pharmacist or nurse.
4.
Possible side effects
Like all medicines, this medicine can cause side effects, although not everybody gets them. Seek immediate medical help if you have any of the following symptoms:
- Fainting or collapse Very common side effects (may affect more than 1 in 10 people):
- Headaches (may occur when this treatment is first started, but these usually disappear after 12 weeks) Common side effects (may affect up to 1 in 10 people):
- Dizziness
- Sleepiness
- Feeling weak
- Fast heartbeat
- Lowering of blood pressure (e.g. feeling dizzy or light-headed) when standing up They may occur for the first few days of treatment or after your dosage has been increased. Uncommon side effects (may affect up to 1 in 100 people):
- Fainting or collapse
- Feeling sick or being sick
- Skin rashes
- Flushing (when your face, ears, neck and, occasionally, your upper chest, become red in colour)
- Increase in chest pain/angina Very rare side effects (may affect up to 1 in 10,000 people):
- Heartburn Other side effects (frequency cannot be estimated from the available data):
- Red or scaly skin (exfoliative dermatitis)
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• • • • • • • •
Low blood pressure Swelling of the skin Stomach upsets Tiredness Uneven heartbeat Looking pale Excessive sweating Restlessness
Reporting of side effects If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible
Possible side effects
not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.
5.
How to store it
Isodur Capsules
Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date, which is stated on the carton and blister foil. The expiry date refers to the last day of that month. Do not use this medicine if you notice that the packaging or any of the capsules are damaged. Store below 25°C. Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.
6.
Contents of the pack and other information
What Isodur Capsules contain The active substance is called isosorbide-5-mononitrate. The other ingredients are sucrose, maize starch, shellac, povidone, ethylcellulose and talc. The capsule shells of Isodur 25XL are made of gelatin and contain the following colourings: titanium dioxide (E171), yellow iron oxide (E172), red iron oxide (E172), black iron oxide (E172). The capsule shells of Isodur 50XL are made of gelatin and contain the following colourings: titanium dioxide (E171), yellow iron oxide (E172), red iron oxide (E172), black iron oxide (E172) and erythrosine (E127).
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The ink on the capsule shells contains: shellac, propylene glycol, strong ammonia solution, potassium hydroxide, titanium dioxide (E171), povidone and sodium hydroxide. Isodur Capsules come in two different strengths of capsule:
- Isodur 25XL Capsules, which contain 25mg of isosorbide-5-mononitrate per prolongedrelease capsule.
- Isodur 50XL Capsules, which contain 50mg of isosorbide-5-mononitrate per prolongedrelease capsule. What Isodur capsules look like and the contents of the pack
- Isodur 25XL Capsules are hard gelatin capsules, which have a brown cap and a white body, with "ISM 25" overprinted in white ink.
- Isodur 50XL Capsules are hard gelatin capsules, which have a brown cap and a red body, with "ISM 50" overprinted in white ink. Isodur 25XL and 50XL Capsules are packaged in calendar/blister packs containing 28 capsules. Marketing Authorisation Holder Galen Limited Seagoe Industrial Estate Craigavon BT63 5UA UK Manufacturer AndersonBrecon (UK) Limited Units 2-7 Wye Valley Business Park Brecon Road Hay-on-Wye Hereford HR3 5PG UK
This leaflet was last revised in 10/2025.
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Frequently asked questions about Isodur 25XL Capsules
How do I take Isodur 25XL Capsules?
Isodur 25XL Capsules comes as capsule. Always follow the dose your doctor or pharmacist has given you, and read the leaflet that comes with the medicine.
What is the active substance in Isodur 25XL Capsules?
The active substance in Isodur 25XL Capsules is isosorbide mononitrate.
Are there equivalent medicines to Isodur 25XL Capsules?
Medicines with the same active substance, strength and form include: Isodur 50XL Capsules, Nyzamac SR Capsules. They are interchangeable only if your prescriber or pharmacist says so.
Where does this information come from?
This leaflet reproduces the patient information leaflet approved for Isodur 25XL Capsules, as published on the electronic medicines compendium (emc). The version printed inside your medicine’s packaging is the one that applies to you.
Can I get Isodur 25XL Capsules without a prescription?
Whether a medicine is available over the counter or on prescription only depends on its licence. Check the leaflet, or ask your pharmacist — they can tell you straight away.
About this leaflet
The text above reproduces the patient information leaflet approved for this medicine, restructured for easier reading.
- Source: electronic medicines compendium (emc), Datapharm
- Active substance: isosorbide mononitrate
- Official document: view the original leaflet on emc →
⚕For healthcare professionals — Summary of Product Characteristics (SmPC)Full SmPC: dosage, interactions, contraindications, warnings+
4.1. Therapeutic indications
For the prophylactic treatment of angina pectoris.
Isodur 25XL Capsules are indicated in adults, including the elderly.
4.2. Posology and method of administration
Posology
Adults:
One capsule to be taken in the morning. For patients with higher nitrate requirements, the dose may be increased to two capsules taken simultaneously. The lowest effective dose should be used.
Attenuation of effect has occurred in some patients being treated with prolonged-release preparations. In such patients intermittent therapy may be more appropriate (see section 4.4).
Treatment with Isodur 25XL Capsules, as with any other nitrate, should not be stopped suddenly. Both dosage and frequency should be tapered gradually (see section 4.4).
Elderly population:
There is no evidence of a need for routine dosage adjustment in the elderly, but special care may be needed in those with increased susceptibility to hypotension.
Paediatric population:
This product is not recommended for use in children. The safety and efficacy of these capsules in children has not yet been established.
Method of administration
For oral use.
The capsules must be swallowed whole and can be taken with water. They must not be chewed or crushed (see section 5.2).
4.3. Contraindications
Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.
This product should not be used in cases of acute myocardial infarction with low filling pressure, acute circulatory failure, shock, vascular collapse or very low blood pressure, hypertrophic obstructive cardiomyopathy (HOCM), constrictive pericarditis, cardiac tamponade, low cardiac filling pressures and aortic/mitral valve stenosis.
This product should not be used in patients with a known sensitivity to nitrates, marked anaemia, diseases associated with a raised intracranial pressure e.g. following a head trauma and including a cerebral haemorrhage.
This product should not be used in patients with closed angle glaucoma, severe hypotension or severe hypovolaemia. Phosphodiesterase type-5 inhibitors (e.g. sildenafil, tadalafil, vardenafil) have been shown to potentiate the hypotensive effects of nitrates, and their co-administration with nitrates or nitric oxide donors is therefore contraindicated (see sections 4.4 and 4.5).
During nitrate therapy, the soluble guanylate cyclase stimulator riociguat must not be used (see section 4.5).
4.4. Special warnings and precautions for use
The capsules should be used with caution in patients who have a recent history of myocardial infarction or low filling pressures e.g. in acute myocardial infarction, impaired left ventricular function (left ventricular failure). Reducing systolic blood pressure below 90 mmHg must be avoided.
This product should be used with caution in patients who are predisposed to closed angle glaucoma, or who are suffering from hypothyroidism, hypothermia, malnutrition or severe liver or renal disease. Symptoms of circulatory collapse may arise after the first dose, particularly in patients with labile circulation. A headache may occur at the start of treatment, but this usually disappears with continued treatment.
This product may give rise to symptoms of postural hypotension and syncope in some patients. Severe postural hypotension with light-headedness and dizziness is frequently observed after the consumption of alcohol.
Hypotension induced by nitrates may be accompanied by paradoxical bradycardia and increased angina.
This product is not indicated for the relief of acute angina attacks. In the event of an acute attack, sublingual or buccal glyceryl trinitrate tablets/sprays should be used instead.
Patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
If the capsules are not taken as indicated (see section 4.2) tolerance to the medication could develop. In some patients being treated with prolonged-release preparations, attenuation of effect is observed. In such patients, intermittent therapy may be more appropriate. The lowest effective dose should be used.
Treatment with Isodur 25XL Capsules, as with any other nitrate, should not be stopped suddenly. Both the dosage and frequency should be tapered gradually (see section 4.2).
In patients with decreased gastrointestinal transit time, a decrease in release of the active ingredient may occur.
Patients on maintenance treatment with this product should be informed that they must not use phosphodiesterase inhibitor-containing products (e.g. sildenafil, tadalafil, vardenafil).
Isodur 25XL Capsules therapy should not be interrupted to take phosphodiesterase inhibitor-containing products (e.g. sildenafil, tadalafil, vardenafil), because the risk of inducing an attack of angina pectoris could increase by doing so (see sections 4.3 and 4.5).
4.5. Interaction with other medicinal products and other forms of interaction
Hypotensive agents e.g beta-blockers, calcium channel blockers, vasodilators, alprostadil, aldesleukin, angiotensin II receptor antagonists etc may potentiate the hypotensive effect of isosorbide-5-mononitrate. This may also occur with alcohol, neuroleptics and tricyclic antidepressants.
The hypotensive effects of nitrates are potentiated by concurrent administration of phosphodiesterase type-5 inhibitors (e.g. sildenafil, tadalafil, vardenafil) (see sections 4.3 and 4.4). This might lead to life threatening cardiovascular complications. Patients who are on Isodur 25XL Capsules therapy therefore must not use phosphodiesterase type-5 inhibitors.
Reports suggest that concomitant administration of isosorbide-5-mononitrate may increase the blood level of dihydroergotamine and its hypertensive effect.
Sapropterin (Tetrahydrobiopterin, BH4) is a cofactor for nitric oxide synthetase. Caution is recommended during concomitant use of sapropterin-containing medicine with all agents that cause vasodilation by affecting nitric oxide (NO) metabolism or action, including classical NO donors (e.g. glyceryl trinitrate (GTN)), isosorbide dinitrate (ISDN), isosorbide-5-mononitrate (ISMN) and others).
The use of isosorbide-5-mononitrate with riociguat, a soluble guanylate cyclase stimulator, is contraindicated (see section 4.3) since concomitant use can cause hypotension.
4.6. Fertility, pregnancy and lactation
Pregnancy
Nitrates have been used widely in the treatment of angina for many years without apparent ill consequence and animal studies have shown no hazard. However, safety in human pregnancy has not been established. This drug should therefore not be used in pregnancy and lactation unless considered essential by the physician.
Breast-feeding
It is unknown whether nitrates are excreted in human milk and therefore caution should be exercised when administered to nursing women.
Fertility
There are no data available on the effect of isosorbide-5-mononitrate on fertility in humans.
4.7. Effects on ability to drive and use machines
Symptoms such as dizziness, tiredness or blurred vision have been reported at the start of treatment with isosorbide-5-mononitrate. Patients should be advised that if affected, they should not drive or operate machinery. This effect may be increased by alcohol.
4.8. Undesirable effects
Undesirable effects frequencies are defined as: very common (≥1/10), common (≥ 1/100 <1/10), uncommon (≥ 1/1,000, <1/100), rare (≥1/10,000 <1/1,000), very rare (<1/10,000), not known (cannot be estimated from the available data).
During the administration of Isodur 25XL Capsules the following undesirable effects may be observed:
Nervous system disorders
Very common
Headache
Common
Dizziness (including dizziness postural), somnolence
Cardiac disorders
Common
Tachycardia
Uncommon
Angina pectoris aggravated
Not known
Palpitations
Vascular disorders
Common
Postural hypotension
Uncommon
Circulatory collapse (sometimes accompanied by bradyarrhythmia and syncope)
Not known
Hypotension
Gastrointestinal disorders
Uncommon
Nausea, vomiting
Very rare
Heartburn
Not known
Abdominal discomfort
Skin and subcutaneous tissue disorders
Uncommon
Allergic skin reactions (e.g. rash), flushing
Not known
Dermatitis exfoliative
Immune system disorders
Not known
Angioedema
General disorders and administration site conditions
Common
Asthenia
Not known
Fatigue
Headache may be minimised by starting with the lower dose and gradually increasing the dose.
Severe hypotensive responses have been reported for organic nitrates and include nausea, vomiting, restlessness, pallor and excessive perspiration.
Temporary hypoxaemia may occur during treatment with isosorbide-5-mononitrate due to a relative redistribution of blood flow in hypoventilated alveolar areas. This may lead to myocardial hypoxia, particularly in patients with coronary artery disease.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
4.9. Overdose
Animal experience:
In rats and mice, significant lethality at oral doses of 1965 mg/kg and 2581 mg/kg, respectively, was observed.
Human experience:
Symptoms:
• Fall of blood pressure ≤ 90 mmHg
• Paleness
• Sweating
• Weak pulse
• Tachycardia
• Light-headedness on standing
• Headache
• Weakness
• Dizziness
• Nausea
• Vomiting
• Diarrhoea
Methaemoglobinaemia has been reported in patients receiving other organic nitrates. During isosorbide-5-mononitrate biotransformation nitrite ions are released, which may induce methaemoglobinaemia and cyanosis with subsequent tachypnoea, anxiety, loss of consciousness and cardiac arrest. It cannot be excluded that an overdose of isosorbide-5-mononitrate may cause this adverse reaction.
In very high doses the intracranial pressure may be increased. This might lead to cerebral symptoms.
General procedure:
• Stop intake of the drug
• General procedures in the event of nitrate-related hypotension
- Patients should be kept horizontal with the head lowered and legs raised
- Supply oxygen
- Expand plasma volume (i.v. fluids)
- Specific treatment for shock (admit patient to intensive care unit)
Special procedure:
• Raising the blood pressure if the blood pressure is very low
• Treatment of methaemoglobinaemia
- To include reduction therapy with methylene-blue, administration of oxygen, initiation of artificial ventilation and haemodialysis, as necessary
• Resuscitation measures
In case of signs of respiratory and circulatory arrest, initiate resuscitation measures immediately.
💬 Ask about this leaflet
Ask anything about Isodur 25XL Capsules. The assistant answers only from this leaflet — if the leaflet does not cover it, it will say so. It does not give medical advice.
Answers come from the patient leaflet published on the electronic medicines compendium (emc). They are not medical advice. Ask a pharmacist or your GP if you are unsure. For urgent help call NHS 111, or 999 in an emergency.
Medicines containing Isosorbide mononitrate
- Carmil XL 60 mg Tablets
- Chemydur 60XL Tablets
- Elantan LA 25 mg prolonged release capsules
- Elantan LA 50 mg prolonged release capsules
- Eumon 40 XL Modified Release Tablets (Isosorbide Mononitrate)
- Imdur Tablets 60mg
- ISMO 10, 10 mg, tablets
- ISMO 20, 20 mg, tablets
- ISMO Retard, 40 mg, prolonged-release tablets
- Isodur 50XL Capsules
- Isosorbide Mononitrate 10 mg Tablet
- Isosorbide Mononitrate 20 mg Tablet
- Isosorbide Mononitrate 40 mg Tablet
- Isosorbide Mononitrate Tablets 10 mg