Calan SR (Verapamil) – Patient Information (UK)

Calan SR contains the medicine verapamil in a sustained-release (SR) form. It is used to help treat certain heart and blood pressure conditions by relaxing blood vessels and slowing the heart rate. This page is written to be easy to read and to help you understand how the medicine works, how it is typically taken, and what to watch for.

Important: Always follow the instructions given by your prescriber and the directions on the medicine label. If you are unsure about your dose or how to take Calan SR, contact your healthcare professional or pharmacist.

Quick Facts

• Active ingredient: Verapamil
• Brand example: Calan SR
• Type: Sustained-release (SR) calcium channel blocker
• Common uses: Angina (chest pain) and some heart rhythm problems; high blood pressure in certain cases
• How it works: Slows the heart and relaxes blood vessels
• How to take: Usually once daily for SR formulations (follow your label)

What Calan SR Is Used For

Verapamil (including SR preparations like Calan SR) is used for several cardiovascular conditions. Your exact indication depends on your diagnosis and medical history.

Typical indications in clinical practice

• Angina pectoris (stable angina): helps reduce the frequency and severity of chest pain episodes.
• Some abnormal heart rhythms (certain supraventricular tachycardias): helps control the rate by slowing electrical conduction in the heart.
• High blood pressure (hypertension): may be used in selected patients, depending on overall health and other treatments.

Note: Verapamil is not suitable for every type of rhythm problem. Some rhythm disorders may require different medicines or urgent assessment.

How Calan SR Works (Mechanism of Action)

Verapamil belongs to the group of medicines called calcium channel blockers. Calcium is involved in how heart muscle contracts and how blood vessels tighten. Verapamil helps by:

• Relaxing blood vessel walls, which can lower blood pressure and reduce strain on the heart.
• Slowing the heart rate by reducing electrical activity through the AV node (the heart’s electrical “relay” point).
• Reducing oxygen demand by making the heart beat more efficiently and less forcefully.

In angina, this may help improve blood flow to the heart muscle and reduce the likelihood of chest pain. For certain tachyarrhythmias, it can help control heart rate and rhythm.

Pharmacokinetics (How the Body Processes Verapamil)

Understanding how verapamil behaves in the body can help you anticipate effects and side effects.

Absorption and sustained release

• Calan SR is designed to release verapamil steadily over time.
• This helps maintain more consistent drug levels throughout the day compared with immediate-release forms.

Metabolism

• Verapamil is primarily metabolised by the liver.
• Because liver metabolism is important, liver impairment may increase drug levels and side effect risk.

Half-life

• Verapamil’s elimination half-life can vary between individuals and may be longer in those with liver impairment.

Elimination

• Breakdown products are eliminated mainly through the kidneys.

Practical takeaway: If you miss a dose or take it at the wrong time, you may experience reduced symptom control or more variable effects. Do not “double up” unless your healthcare professional tells you to.

When and How to Take Calan SR

Timing

• Calan SR SR is commonly taken once daily, often in the morning or evening depending on your doctor’s instructions.
• Try to take it at the same time each day to keep effects steady.

How to take

• Swallow the tablet whole with water.
• Do not crush, chew, or split sustained-release tablets unless specifically instructed—this can release the medicine too quickly.

Typical starting and dose adjustments

Different patients require different doses. Your regimen depends on your age, kidney and liver function, other medicines, and the condition being treated.

• Doses are often increased gradually based on response and tolerability.
• The maximum daily dose for SR preparations varies with indication and local prescribing practices—always follow your label.

Dosing Guidance (General Information)

Because dosing is individual, the table below provides general context about verapamil SR regimens commonly used in practice. Your prescription label is the most reliable source.

Missed dose: If you miss a dose, take it when you remember unless it is close to the time for your next dose. In that case, skip the missed dose—do not take a double dose.

Stopping treatment: Do not stop suddenly unless advised by a clinician. Sudden changes can worsen symptoms in some heart conditions.

Food Interactions

Food can affect how quickly and how much verapamil your body absorbs, which can influence blood levels and side effects.

• Grapefruit and grapefruit juice: may increase verapamil levels and side effect risk. It is generally best to avoid grapefruit products.
• Alcohol taken with or around doses (see below) can further increase risks such as dizziness and low blood pressure.
• Other foods are not usually a major issue, but maintaining a consistent routine can help.

Tip: Take Calan SR the way you were instructed—either consistently with or without food—unless your pharmacist advises otherwise.

Alcohol and Medicine Interactions

Alcohol

Alcohol may intensify some side effects of verapamil, such as:

• Dizziness or light-headedness
• Low blood pressure
• Feeling faint
• Reduced alertness

If you drink alcohol, consider keeping amounts moderate and watch how you feel—especially when starting treatment or after dose changes.

Common medicine interactions

Verapamil interacts with several medicines. Some interactions can significantly raise verapamil levels, increasing risk of bradycardia (slow heart rate), dizziness, or heart block; others may reduce its effectiveness.

Always tell your pharmacist or healthcare professional about all medicines you take, including over-the-counter products and herbal remedies.

• Other heart medicines: beta-blockers (e.g., metoprolol, bisoprolol), digoxin, and antiarrhythmics may increase risk of slow heart rate or conduction problems when combined.
• Medicines affecting heart rhythm: certain antiarrhythmics can add to effects on conduction.
• Medicines that affect liver enzymes: some antibiotics, antifungals, and antivirals can change verapamil metabolism.
• Blood pressure medicines/vasodilators: may increase the likelihood of low blood pressure.
• Statins: some statins may have increased exposure when used with verapamil, raising risk of muscle-related side effects.
• Carbamazepine, phenytoin, and certain other anticonvulsants: may affect verapamil levels.

Herbal products and supplements: In particular, supplements that affect heart rate or blood pressure, and herbal preparations that influence liver enzymes, can interact. Ask your pharmacist for guidance.

Safety Profile: What to Watch For

Most people tolerate verapamil well, but it can cause side effects—especially at the start or when the dose is increased.

Common side effects

• Constipation (a common effect of verapamil)
• Headache
• Dizziness or light-headedness
• Flushing
• Swelling of ankles/feet (fluid retention)
• Feeling tired

Serious side effects (seek urgent medical advice)

Get urgent help if you experience symptoms that could indicate a dangerous rhythm problem or low blood pressure, such as:

• Fainting or severe dizziness
• Very slow heartbeat or palpitations with feeling unwell
• Chest pain worsening significantly
• Shortness of breath or sudden breathlessness
• Severe swelling or signs of an allergic reaction (e.g., swelling of face/lips, rash, difficulty breathing)

Special caution groups

• Liver impairment: may require dose adjustments and closer monitoring.
• Heart conduction problems: may increase risk of heart block; ECG monitoring may be required.
• Low blood pressure: may worsen symptoms such as dizziness.
• Older adults: may be more sensitive to dizziness and constipation.
• People with heart failure: your clinician will consider suitability and monitoring.

Driving and operating machinery: if Calan SR makes you dizzy or affects your alertness, avoid driving or hazardous activities until you know how it affects you.

Practical Use Tips (Everyday Advice)

Manage constipation early

Constipation is a frequent reason people stop or dislike verapamil. Practical steps include:

• Drink adequate fluids.
• Increase dietary fibre gradually.
• Consider gentle activity if safe for you.
• If needed, ask your pharmacist about suitable laxatives or stool softeners.

Track heart rate and blood pressure (if advised)

If you are taking verapamil for rhythm or blood pressure:

• Use a home blood pressure monitor if recommended.
• Report consistent low readings or troublesome symptoms to your clinician.

Be careful with dose timing after changes

• If you start Calan SR or increase your dose, side effects may happen more in the first days or weeks.
• Stand up slowly from sitting or lying down to reduce dizziness.

Keep an up-to-date medicine list

Bring your medicine list to appointments and check any new medicine with your pharmacist—especially antibiotics, antifungals, antivirals, and antiarrhythmics.

Alternative Options

Depending on your diagnosis, your clinician may consider other treatments. Alternatives may include:

• Other calcium channel blockers: e.g., amlodipine (often for hypertension/angina), though it has different effects on heart rate.
• Beta-blockers: sometimes used for angina and rate control in certain arrhythmias.
• Other antianginal medicines: such as nitrates or other classes (choice depends on your heart condition).
• Rhythm-specific treatments: additional antiarrhythmic medicines or procedures may be considered for certain arrhythmias.

Important: Don’t switch between medicines without medical guidance. Verapamil SR dosing and monitoring requirements differ from other options.

UK Market, Legal and Prescribing Context

In the UK, verapamil products are widely available and are commonly used under clinical supervision. Availability of Calan SR or equivalent verapamil SR brands can vary by stock and supply agreements with manufacturers and wholesalers.

Regulatory oversight: Medicines in the UK are regulated and must meet safety, quality, and effectiveness standards. Pharmacy dispensing is guided by the UK’s medicines framework, including information provided in patient information leaflets and product summaries.

Recent guidance and monitoring trends (general):

• There is continued emphasis on careful cardiovascular monitoring (e.g., ECG review when appropriate), especially when starting or adjusting dose.
• Clinicians typically review drug interaction risk more thoroughly, particularly with medicines that affect liver metabolism or heart rhythm.
• Constipation management advice remains common for patients on verapamil.

If you want to confirm how current UK guidance applies to your situation, ask your pharmacist or clinician.

Delivery and Availability (Online Pharmacy)

Availability can depend on whether Calan SR is currently in stock at distribution centres and whether specific strengths are required. On an online pharmacy website, you may see:

• In-stock availability: dispatch typically occurs quickly after ordering during working days.
• Back-order or alternative strength/brand options: if the exact product is temporarily unavailable, your pharmacy may offer an alternative if clinically appropriate and allowed.
• Delivery updates: tracking information and estimated delivery windows are often provided after dispatch.

Storage: Keep verapamil tablets in a safe place at room temperature, away from moisture and heat, and out of the sight and reach of children. Follow the patient leaflet for specific storage instructions.

FAQ – Frequently Asked Questions

1) What is Calan SR used for?

Calan SR (verapamil) is used for conditions such as angina (chest pain) and some heart rhythm problems. It may also be used for hypertension in selected patients.

2) How fast will it start working?

Some people notice improvements in symptoms like chest discomfort or heart rate control within days, while consistent benefit for blood pressure and angina may take longer. If your symptoms change suddenly or worsen, contact your healthcare professional.

3) Can I stop taking Calan SR if I feel better?

Do not stop suddenly unless you are advised to do so. Stopping can lead to return of symptoms or worsening of heart-related conditions.

4) What should I do if I miss a dose?

Take it when you remember unless it is close to your next dose. Do not take a double dose to make up for a missed tablet.

5) Are grapefruit products safe with verapamil?

Grapefruit and grapefruit juice can increase verapamil levels, potentially raising side effect risk. It is generally recommended to avoid grapefruit while taking verapamil.

6) Can I drink alcohol while taking Calan SR?

Alcohol can increase dizziness and lower blood pressure. If you choose to drink, do so in moderation and pay attention to how you feel—particularly when starting treatment or changing dose.

7) What are the most common side effects?

Common side effects include constipation, headache, dizziness, flushing, ankle/foot swelling, and tiredness.

8) When should I seek urgent help?

Seek urgent medical advice if you faint, feel severely dizzy, experience very slow heartbeat, have severe chest pain, become breathless, or show signs of an allergic reaction.

9) Will Calan SR interact with other medicines?

Yes. Verapamil interacts with several medicines, including some heart medicines and drugs that affect liver enzymes. Always provide your pharmacist with a list of everything you take.

10) Is it okay to crush or split Calan SR tablets?

No—because it is a sustained-release product, you should swallow it whole. Crushing or splitting can change how the medicine releases in your body.

Final reminder: This page provides general information about Calan SR (verapamil). Individual advice may differ based on your medical history, other medicines, and your specific diagnosis. If you have questions about suitability, dosing, interactions, or side effects, ask your pharmacist or healthcare professional.