Calan SR (Verapamil) – Patient Information

Calan SR contains verapamil as a sustained-release (SR) medicine. It is used to help control certain heart rhythm problems and high blood pressure. This page explains how it works, how to take it safely, and what to expect. It is written for people in the United Kingdom.

What is Calan SR?

Calan SR is a medicine containing verapamil. Verapamil helps relax blood vessels and reduces the heart’s workload. Because it is sustained-release, the medicine is released gradually over time to help maintain steadier levels in the body.

The exact strength and form you receive (for example, 120 mg, 180 mg, 240 mg SR) depends on your individual needs. Always follow the dosing instructions provided with your product.

How Calan SR works (Mechanism of Action)

Verapamil belongs to the group of medicines called calcium channel blockers, specifically non-dihydropyridines (such as verapamil and diltiazem).

• Blood vessels: It reduces calcium entry into smooth muscle cells in blood vessel walls. This leads to relaxation of blood vessels and helps lower blood pressure.
• Heart: It slows the electrical conduction through the AV node (atrioventricular node). This can help control certain rhythm disorders and may reduce the heart rate.
• Heart muscle oxygen demand: By lowering workload and easing blood flow, it can help reduce symptoms in conditions where the heart needs more oxygen (such as some types of angina).

Pharmacokinetics (How the body handles the medicine)

Understanding how verapamil behaves in the body can help explain why timing, consistency, and interactions matter.

• Absorption: With SR formulations, verapamil is released slowly. Absorption may be affected by food and by other medicines.
• Distribution: Verapamil distributes throughout body tissues and has a high protein-binding profile.
• Metabolism: Most verapamil is metabolised in the liver, mainly by enzymes of the CYP family (including CYP3A4). This is why some drugs and certain foods can raise or lower its levels.
• Elimination: Metabolites are primarily removed through the kidneys (and to some extent via the bile/faeces).
• Steady effect: With SR products, effects may be smoother across the day compared with immediate-release tablets.

Typical uses (Indications)

Calan SR is used for several cardiovascular conditions. The most common approved uses in clinical practice include:

• Hypertension (high blood pressure): To help reduce blood pressure and lower cardiovascular risk.
• Angina: In some patients, to help reduce chest pain episodes (particularly where a doctor considers verapamil appropriate).
• Certain rhythm disorders: Verapamil can help control supraventricular tachycardia and other rhythm issues where slowing AV-node conduction is beneficial.

Important: Not all heart rhythm problems are suitable for verapamil. If you have a history of certain arrhythmias or conduction problems, your clinician may choose alternatives.

Timing and how to take Calan SR

Because Calan SR is a sustained-release medicine, how you take it matters.

• Once daily (often): Many people take SR verapamil once daily, typically at the same time each day.
• Follow your schedule: Use the dose and timing advised for you.
• Swallow whole: Do not crush, chew, or break SR tablets/capsules unless your product information specifically allows it.
• If you miss a dose:
  • Take it when you remember if it is not close to the next dose.
  • If it is nearly time for the next dose, skip the missed dose and continue as normal.
  • Do not take a double dose to make up for a missed one.

Practical tips for everyday use

• Choose a routine: Many people prefer taking it at breakfast or in the evening—pick a time you can keep consistently.
• Keep tablets in original packaging: Protect from moisture and ensure correct identification.
• Use reminders: Phone alarms can help reduce missed doses.
• Monitor symptoms: Keep track of blood pressure readings and any rhythm symptoms (palpitations, dizziness, breathlessness) to discuss at review appointments.

Food interactions (including grapefruit and other considerations)

Food and drink can influence how much verapamil is absorbed and how long it lasts.

• Grapefruit and grapefruit juice: These can increase verapamil levels because they affect liver enzymes involved in drug metabolism. This may raise the risk of side effects such as dizziness, low blood pressure, or slowed heart rate.
• General meals: Taking SR verapamil with or without food may be acceptable for many people, but individual product information and clinician advice should be followed.
• Alcohol-containing foods/drinks: Alcohol can worsen dizziness and may increase side-effect risk (see below).

Tip: Try to keep your usual approach to taking verapamil with meals consistent unless your healthcare professional advises otherwise.

Alcohol and medicine interactions

Verapamil can lower blood pressure and slow heart rate. Alcohol can also lower blood pressure and may worsen dizziness or light-headedness, especially when you start treatment or increase your dose.

Alcohol

• Be cautious: Limit alcohol, particularly during the first days of treatment.
• Avoid binge drinking: This increases the risk of fainting, falls, and interaction-related side effects.
• Watch for symptoms: If you feel unusually dizzy, weak, or faint, avoid alcohol and speak to your clinician.

Other medicine interactions (common and important examples)

Verapamil levels and heart conduction can be affected by other medicines. Always check interactions with your pharmacist or clinician, including over-the-counter products and herbal remedies.

• Other medicines that slow the heart: Combining verapamil with drugs that slow heart rate (such as certain beta-blockers or other rate-slowing medicines) may increase the risk of too-slow heart rate or conduction problems.
• Digoxin: Verapamil can increase digoxin levels. This may require monitoring and dose adjustments.
• Antiarrhythmics: Some rhythm medicines may increase the risk of conduction disturbances.
• Statins (cholesterol-lowering drugs): Some statins may interact with verapamil metabolism, increasing the risk of statin side effects in certain combinations.
• Antihypertensives: Using verapamil alongside other blood pressure medicines can increase the likelihood of low blood pressure.
• CYP3A4 inhibitors: Medicines that inhibit CYP3A4 can raise verapamil levels (e.g., certain antibiotics/antifungals and some other cardiovascular and GI medications). This can increase side effects.
• CYP3A4 inducers: Medicines that increase CYP3A4 activity can reduce verapamil levels, making it less effective.
• Some antidepressants and antipsychotics: Depending on which one, interactions may occur through metabolism or effects on blood pressure/heart rhythm.

Herbal products: St John’s wort may reduce effectiveness of some medicines by inducing liver enzymes. Ask your pharmacist before using herbal remedies.

Dosing (how much is used)

Dosing varies based on the condition being treated, your age, kidney/liver function, and your response to therapy. Your clinician will specify the exact dose for you.

General principles for SR verapamil dosing:

• Start low, increase gradually: This helps reduce the chance of side effects such as dizziness or low blood pressure.
• Do not change dose without advice: Adjustments should be made by a clinician after monitoring heart rate, blood pressure, and symptoms.
• Adherence is important: Because SR tablets provide a steady release, taking them consistently helps maintain effect.

Common clinical dosing ranges (approximate):

• For many adults with hypertension or angina, SR verapamil is often used in once-daily dosing with strengths such as 120 mg, 180 mg, or 240 mg depending on needs.
• For rhythm control, your clinician may use SR verapamil in a similar once-daily schedule, or use alternative dosing strategies based on the specific arrhythmia and response.

Note: These ranges are provided for general understanding. Your product label and prescriber instructions are the authoritative source for your dose.

Safety profile (side effects and when to seek help)

Like all medicines, Calan SR can cause side effects. Many people experience mild effects that improve as the body adjusts, but some symptoms may indicate a serious problem.

Common side effects

• Headache
• Dizziness or light-headedness
• Swelling (oedema), especially in the ankles/legs
• Constipation (a known effect with verapamil in some people)
• Feeling tired
• Flushing

Less common but important effects

• Low blood pressure (may cause dizziness, fainting)
• Slow heart rate (bradycardia)
• Worsening heart failure symptoms in susceptible individuals (breathlessness, swelling, sudden weight gain)
• Abnormal heart conduction (palpitations, fainting, unusual fatigue)

Seek urgent medical help if you have

• Fainting or severe dizziness
• Chest pain that is new/worse or accompanied by breathlessness/sweating
• Severe shortness of breath, pink frothy sputum, or sudden worsening swelling
• Very slow pulse, or heart rhythm symptoms with weakness or collapse
• Allergic reaction signs: swelling of face/lips, hives, difficulty breathing

Special caution groups

• People with conduction problems: such as heart block or significant bradycardia
• Those with heart failure: verapamil can worsen symptoms in certain cases
• Older adults: may be more sensitive to blood pressure-lowering effects
• Liver impairment: affects metabolism and may require dose adjustments and closer monitoring

Practical use tips to improve safety

• Check your pulse and blood pressure: Especially after starting treatment or changing dose.
• Stand up carefully: If you feel light-headed, rise slowly from sitting or lying positions.
• Manage constipation: Drink adequate fluids, include fibre, and consider a suitable laxative strategy if constipation develops—ask your pharmacist.
• Keep track of symptoms: Note any new palpitations, fatigue, swelling, or breathlessness.
• Tell healthcare professionals: Let dentists, pharmacists, and clinicians know you take Calan SR, particularly before procedures or if you are started on new medicines.

Monitoring (what follow-up may include)

Your clinician may monitor:

• Blood pressure and, in some cases, heart rate
• Electrocardiogram (ECG) for rhythm/conduction assessment, particularly when starting or adjusting dose
• Signs of fluid retention if you have heart failure risk
• Liver function if you have known liver impairment or are on multiple medicines

Alternative options (if Calan SR is not suitable)

Depending on why you are taking verapamil, there are alternative medicines and strategies. Your clinician will choose based on your condition, medical history, and interactions.

For high blood pressure

• Other calcium channel blockers: such as amlodipine (a different class and different interaction profile)
• ACE inhibitors or ARBs
• Thiazide-like diuretics
• Beta-blockers (chosen carefully, especially in combination therapy)

For rhythm disorders

• Other rate-controlling medicines (e.g., beta-blockers in selected cases)
• Rhythm-specific antiarrhythmic options depending on the type of arrhythmia
• Non-medicine options in some cases (e.g., procedures like catheter ablation), guided by specialist cardiology

For angina

• Nitrates for symptom relief
• Other anti-anginal medicines such as beta-blockers or longer-acting therapies depending on suitability
• Lifestyle measures (stop smoking, manage blood pressure, physical activity plan) alongside medication

Do not stop Calan SR suddenly unless advised. If you feel you need to change treatment, speak to a clinician or pharmacist for a safe plan.

United Kingdom market and legal context

Calan SR (verapamil) is an established cardiovascular medicine used within the UK healthcare system. Medicines classification and prescribing arrangements in the UK can vary by product form and strength.

• Availability: Verapamil SR products are typically supplied through UK pharmacies in line with UK medicines regulations.
• Care pathway: Heart conditions often require ongoing assessment, including blood pressure and heart rhythm monitoring.
• Pharmacist support: UK pharmacists can help check for interactions, advise on safe use, and guide you on what to monitor.

Recent guidance and practice considerations (general): Current UK clinical practice emphasises careful assessment of cardiovascular risks, consideration of drug–drug interactions, and monitoring for bradycardia/hypotension or worsening heart failure where relevant.

Delivery and availability (online pharmacy)

When ordering online in the UK, availability can vary due to stock levels and supply schedules. Many pharmacies follow standard processes to ensure:

• Correct product selection: strength and SR formulation are correct
• Packaging integrity: tablets/capsules are supplied in original packaging
• Discreet packaging: where applicable
• Tracking: deliveries often include tracking options

Delivery times: These differ by provider and location. Check the delivery information shown at checkout for the most accurate estimate. If a product is temporarily unavailable, the pharmacy may contact you or offer an appropriate alternative.

FAQ – Frequently Asked Questions

1) How long does Calan SR take to work?

Many people notice effects on symptoms or blood pressure over the first days. However, full benefit may take longer and depends on the reason you’re taking it and your individual response. Keep taking it consistently and discuss persistent symptoms with your clinician.

2) Can I take Calan SR with food?

Usually, yes, but try to follow the routine you have been advised. Certain drinks like grapefruit juice should be avoided because they can raise verapamil levels.

3) What if I forget a dose?

Take it when you remember if it is not near the time of your next dose. Otherwise, skip the missed dose. Do not take a double dose.

4) Can I drink alcohol while taking verapamil?

You can, but be cautious. Alcohol may increase dizziness and lower blood pressure. Limit intake, especially when you first start or after dose changes. If you feel unwell, avoid alcohol and seek advice.

5) What medicines should I avoid?

Check interactions with your pharmacist, especially with medicines that slow the heart, affect liver enzymes, or raise verapamil levels. Examples include certain antibiotics/antifungals, digoxin, and other blood pressure medicines. Herbal products like St John’s wort may also interact.

6) Are there any signs that my dose is too strong?

Possible signs include marked dizziness, fainting, very slow pulse, or worsening breathlessness or swelling. If you experience these, contact urgent medical services or seek prompt medical advice.

7) Will verapamil cause constipation?

It can. If constipation occurs, drink fluids, increase fibre, and discuss safe options with a pharmacist.

8) Can I stop Calan SR suddenly?

Do not stop without medical advice. Stopping abruptly may worsen symptoms for some conditions. If you want to discontinue, talk to your clinician about a safe plan.

9) Is Calan SR safe for everyone?

Not necessarily. People with certain heart conduction problems, certain types of arrhythmias, or specific heart failure situations may not be suitable. Liver impairment also requires extra caution.

10) What should I do if I feel dizzy after taking it?

Sit or lie down, avoid driving until you feel normal, and monitor your blood pressure and pulse if possible. If dizziness is severe, fainting occurs, or symptoms persist, seek medical advice.

Summary

Calan SR (verapamil) is a sustained-release calcium channel blocker used in the UK to treat conditions such as high blood pressure, angina, and certain heart rhythm disorders. It works by reducing calcium activity in heart and blood vessel cells, helping relax vessels and slow conduction through the heart.

For best safety and effectiveness, take it as directed (swallow SR tablets whole), keep your routine consistent, avoid grapefruit, and be mindful of interactions with alcohol and other medicines. If you experience symptoms like fainting, severe dizziness, or worsening breathlessness, seek urgent medical help.