Imdur (Isosorbide) – Patient Information Guide (UK)

Imdur is a brand of medicine containing isosorbide, a nitrate used to prevent certain types of chest pain (angina). This patient-friendly guide explains what Imdur is used for, how it works, how it is taken, and what to consider for safety and interactions in the United Kingdom.

Important: Always follow the advice of your healthcare professional and the instructions on the pack. This information is for education and should not replace medical guidance.

Quick overview

• Active ingredient: Isosorbide (often as isosorbide mononitrate in controlled-release products)
• Medicine class: Nitrate (anti-anginal)
• Common reason for use: Prevention of angina (chest pain) and reduction in episodes
• Form: Typically controlled-release/extended-release tablets (depending on the specific strength)
• How it works: Relaxes blood vessels to improve blood flow to the heart

Basic product information

How Imdur works (mechanism of action)

Imdur belongs to the nitrate medicines. Nitrates work mainly by:

• Relaxing blood vessels (especially veins, and also some arteries), which lowers resistance to blood flow and reduces the workload on the heart.
• Increasing blood supply to the heart muscle by improving blood flow and decreasing “oxygen demand” during angina.
• Promoting nitric oxide signalling, which triggers smooth muscle relaxation in vessel walls.

Because Imdur is designed to release medicine over time, it is often used as a long-acting preventive treatment for angina.

Pharmacokinetics: how your body handles Imdur

Pharmacokinetics describes what the body does to the medicine—how it is absorbed, processed, and eliminated.

• Absorption: Imdur is typically formulated to provide gradual release. Controlled-release preparations help maintain steadier nitrate levels throughout dosing intervals.
• Distribution: Isosorbide distributes through the body, including cardiovascular tissues.
• Metabolism: The body metabolises isosorbide mainly in the liver.
• Excretion: Metabolites are eliminated primarily via the kidneys (urine).

Practical implication: Controlled-release formulations are designed to provide ongoing protection. Missing doses or taking them at irregular times may reduce the benefit.

Typical use in the UK

Imdur is used to help prevent angina attacks and improve exercise tolerance in people with coronary artery disease.

It may be used:

• When angina is chronic and recurring
• In combination with other anti-anginal medicines (for example, beta-blockers or calcium channel blockers), depending on your individual plan
• As part of long-term management to reduce the frequency of chest pain episodes

Note: Long-acting nitrate tablets like Imdur are usually not intended for immediate relief during an acute angina attack. If you experience sudden chest pain, follow the emergency plan provided by your healthcare professional.

When to take Imdur (timing guidance)

Always take Imdur exactly as directed on your prescription instructions or the product label.

• Consistency is important: Try to take it at the same times each day.
• Controlled-release tablets: Swallow whole—do not crush or chew unless your specific product instructions say otherwise.
• Evening doses: Some regimens may include doses later in the day. If you get dizziness at specific times, discuss timing with your clinician.

Why “nitrate-free” time matters

Nitrates can cause tolerance (reduced effect) with continuous exposure. To help reduce this risk, regimens often include a nitrate-free interval (a time where nitrates are less active). Your dosing schedule is selected to balance prevention of angina with reduced tolerance.

• Do not adjust the schedule on your own.
• If angina symptoms worsen or you feel side effects are affecting you, seek advice rather than changing the dose independently.

Food interactions

In general, nitrates like isosorbide are not strongly affected by food. Many people take Imdur with or without food.

• If you experience nausea or stomach upset: Taking your dose with food may help.
• Avoid sudden changes: Keep your routine steady, especially if your healthcare team has already adjusted your dose for symptom control.

Tip: If your tablets are controlled-release, ensure you follow the instructions on swallowing and timing carefully.

Alcohol interactions

Alcohol can increase the likelihood of dizziness and low blood pressure, which are known potential side effects of nitrates.

• Use caution: If you drink alcohol, start with small amounts and see how you feel.
• Avoid binge drinking: This increases risk of fainting, falls, and cardiovascular stress.
• Get urgent help if you faint or have severe dizziness.

Medicine interactions: key considerations

Several medicines can interact with nitrates by affecting blood pressure, blood vessel tone, or nitrate tolerance. Always tell your pharmacist or prescriber about all medicines you take, including over-the-counter products and herbal remedies.

Absolute or major concern: PDE-5 inhibitors

Do not combine isosorbide nitrates with medicines used for erectile dysfunction or pulmonary hypertension that belong to the PDE-5 inhibitor class (for example, sildenafil, tadalafil, vardenafil). This combination can cause a dangerous drop in blood pressure.

• If you use PDE-5 inhibitors, discuss alternatives urgently with a clinician.

Blood pressure–lowering medicines

Imdur may add to the blood-pressure-lowering effects of:

• Other medicines for angina or heart disease
• Some blood pressure medicines (antihypertensives)
• Some antidepressants or antipsychotics that can affect blood pressure

What you may notice: dizziness, light-headedness, or feeling faint—especially after standing up.

Riociguat (pulmonary hypertension medicine)

Riociguat can interact with nitrates and is generally contraindicated due to risk of significant hypotension. Your clinician should advise on safe alternatives.

Other nitrates and tolerance

• Using more nitrate products than advised may increase side effects.
• Continuous nitrate exposure may reduce effectiveness (tolerance). Your regimen is usually planned to minimise this.

Common practical interaction checks

• Provide your full medication list to your pharmacist when collecting Imdur.
• Check with a pharmacist before starting new medicines (including “cold/flu” products that may contain ingredients affecting blood pressure).

Indications: when Imdur is used

The main indication for Imdur is to prevent angina in people who experience episodes due to reduced blood supply to the heart.

Depending on your medical history and local treatment plan in the UK, Imdur may be used:

• For stable angina as part of ongoing therapy
• To reduce frequency of angina attacks and improve ability to exercise
• In selected cases as part of a multi-drug anti-anginal regimen

Dosing: how much to take

Dose depends on your age, symptoms, blood pressure, and the exact Imdur formulation and strength. Follow the dosing schedule given by your healthcare professional.

• Typical approach: Starting at a lower dose may be used to reduce side effects like headache or dizziness.
• Maintenance: Dose may be adjusted based on symptom control.
• Do not double up: If you miss a dose, take it when you remember unless it is close to the next dose. Do not take two doses at once.

If you are unsure: Check the pack and your instructions. Your pharmacist can explain the regimen.

Safety profile: side effects and what to do

Like all medicines, Imdur can cause side effects. Many are mild and improve as your body adjusts, but some may require urgent action.

Common side effects

• Headache (very common with nitrates)
• Dizziness or feeling light-headed
• Flushing (warmth or redness)
• Low blood pressure (especially when standing)

Less common but important effects

• Palpitations
• Weakness or fatigue
• Nausea
• Swelling (rare, but discuss persistent swelling)

Seek urgent medical help if

• You faint or have severe dizziness
• You develop severe allergic-type reactions (swelling of face/lips, difficulty breathing)
• Chest pain becomes severe, different from your usual angina, or does not improve as advised in your action plan

How to reduce common side effects

• Stand up slowly, especially after sitting or lying down.
• Stay hydrated (unless you have a fluid restriction from your clinician).
• If headaches occur, they often lessen after repeated dosing—however, severe or persistent headaches should be discussed with your pharmacist or doctor.
• Avoid alcohol which may worsen dizziness and blood-pressure changes.

Practical use tips

• Take at the right time: Controlled-release benefit depends on consistent dosing.
• Swallow whole: Do not crush or chew controlled-release tablets unless instructed.
• Keep track of angina: Note frequency, triggers, and timing of chest pain episodes to support safe dose optimisation.
• Do not stop suddenly: If you stop long-acting anti-anginal medicine without advice, angina may worsen. Discuss changes with your clinician.
• Be careful when driving: If you experience dizziness, avoid driving until you know how you respond.

Over time: tolerance and “nitrate-free” intervals

With long-term nitrate use, some people may develop tolerance, where the benefit reduces. To minimise this, your dosing schedule may include a daily period with no nitrate exposure.

• Follow your prescribed dosing interval.
• If angina is increasing, do not simply take extra doses—contact your healthcare professional.
• If you forget a dose, do not try to “catch up” with additional tablets.

Alternative options for angina prevention (UK context)

There are different medicines used to prevent angina. The most suitable option depends on your heart function, blood pressure, other conditions, and symptom pattern.

Common alternatives or add-ons

• Beta-blockers (e.g., bisoprolol, metoprolol): reduce heart rate and oxygen demand
• Calcium channel blockers (e.g., amlodipine): help relax blood vessels and may reduce frequency of angina
• Other long-acting nitrates (e.g., patches or other formulations): choice depends on tolerance and dosing convenience
• Ranolazine: used in selected patients for stable angina
• Ivabradine in selected cases (mainly to reduce heart rate)

Non-medicine approaches can also help, such as smoking cessation, regular appropriate exercise plans, weight management, and managing blood pressure and cholesterol.

Market and legal context in the United Kingdom

In the UK, medicines are regulated and supplied under national frameworks. Anti-anginal medicines like Imdur are used widely within routine care pathways for angina management.

• Regulation: Medicines are authorised and monitored for quality, safety, and effectiveness.
• Information: Patient leaflets and Summary of Product Characteristics (SmPC) guide safe use.
• Pharmacy supply: Pharmacists support safe supply and can advise on interactions and correct timing.

Online pharmacy note: When ordering online, ensure your details are accurate and that your pharmacist can contact you if clarification is needed for safe use.

Recent guidance and ongoing care

UK clinical practice for angina management may be updated over time by professional guidance and formulary recommendations. Key themes that typically remain consistent include:

• Using anti-anginal medicines to reduce symptoms and improve quality of life
• Considering the role of nitrates alongside other evidence-based medicines
• Being mindful of nitrate tolerance and dosing schedules
• Minimising dangerous interactions (especially with PDE-5 inhibitors)

If you have angina, it’s also important to review overall cardiovascular risk factors with your healthcare team (for example cholesterol and blood pressure), as prevention of future heart events is broader than symptom control alone.

Delivery and availability (UK)

Availability can vary by strength and pack size. Many online pharmacies in the UK aim to keep common strengths in stock, but delivery times may differ depending on supply and your location.

• Stock status: Check the product page for current availability.
• Delivery options: Standard or express delivery may be offered; cut-off times can apply.
• Packaging: Medicines are typically dispatched in secure, tamper-evident packaging.
• Storage: Store as directed on the pack (generally at room temperature, away from heat and moisture).

Delivery tip: If you’re taking Imdur every day, consider ordering early to avoid running out—especially if delivery schedules are longer in your area.

FAQ

What is Imdur used for?

Imdur is used to help prevent angina (chest pain) by improving blood flow and reducing the heart’s workload. It is designed for long-term symptom prevention rather than instant attack relief.

How long does Imdur take to work?

Because Imdur is usually controlled-release, it is designed for sustained prevention over the dosing interval. Your clinician can advise on what to expect for symptom control. If you need immediate relief during an attack, follow your separate action plan for acute symptoms.

Can I take Imdur if I have low blood pressure?

Imdur can lower blood pressure. If you already have low blood pressure or feel faint, tell your healthcare professional. They may adjust your dose or timing and monitor you for dizziness.

Can I drink alcohol while taking Imdur?

Alcohol can increase dizziness and low blood pressure. Use caution, and avoid heavy drinking. If you feel faint or unusually dizzy, seek medical advice.

What should I do if I miss a dose?

Take the missed dose when you remember unless it is close to the next scheduled dose. Do not take two doses at once. If you’re unsure, ask a pharmacist for advice.

Does food affect Imdur?

Food is not usually a major issue. If you find it upsets your stomach, you may take it with food—while keeping to your usual routine.

What side effects are common?

The most common side effects include headache, dizziness, and flushing. These can be stronger at the start of treatment and may improve over time.

Is it safe to take Imdur with medicines for erectile dysfunction?

No. Imdur must not be taken with PDE-5 inhibitors (such as sildenafil or tadalafil) due to risk of dangerous blood pressure lowering. Discuss alternatives with a clinician urgently.

Can I stop Imdur suddenly?

Do not stop without medical advice. Stopping nitrates can lead to a return or worsening of angina symptoms. If you want to stop or change therapy, speak to your healthcare professional.

Are there alternatives if Imdur causes side effects?

Yes. Options may include other anti-anginal medicines (such as beta-blockers, calcium channel blockers, or other therapies). A clinician can recommend alternatives based on your symptoms and overall health.

When should I seek urgent medical help?

Seek urgent help if you faint, have severe dizziness, signs of an allergic reaction, or if chest pain becomes severe, unusual, or does not follow your established plan.

Summary

Imdur (isosorbide) is a long-acting nitrate medicine used to prevent angina by relaxing blood vessels and reducing the heart’s oxygen demand. It works best when taken at the recommended times and often includes a dosing schedule designed to reduce tolerance. Common side effects include headache and dizziness, and safety is especially important with medicines that can dangerously lower blood pressure—particularly PDE-5 inhibitors.

If you have questions about taking Imdur safely, interactions, or whether it suits your angina plan, your pharmacist is a good first point of contact.