Calan SR (Verapamil) – Patient Information (Australia)

Calan SR is a brand of verapamil in a slow‑release (SR) form. It is used to help control certain heart rhythm and blood pressure conditions. Because it acts on the heart’s electrical system and blood vessels, it can affect heart rate, blood pressure and circulation. This guide explains how Calan SR works, how it’s typically taken, important safety information, and what to watch for.

This information is general and designed to be patient-friendly. Always follow the instructions provided with your medicine and the advice of your healthcare professional.

Basic product information

How Calan SR works (mechanism of action)

Verapamil is a calcium channel blocker (specifically, it primarily affects slow calcium channels in the heart and blood vessels). Calcium entry into heart muscle cells and certain cells involved in heart rhythm helps drive contraction and electrical signalling. By blocking these channels, verapamil:

• Slows the heart rate by reducing conduction through the AV node (atrioventricular node).
• Helps control certain abnormal heart rhythms that rely on AV node conduction.
• Relaxes blood vessels, which can lower blood pressure.
• May reduce the heart’s workload by lowering vascular resistance and affecting heart contraction.

The “SR” formulation is designed to release the medicine gradually, which can support more consistent blood levels over the day.

Pharmacokinetics (how the body absorbs and handles it)

Pharmacokinetics describes what the body does to a medicine—absorption, distribution, metabolism, and elimination.

• Absorption: Calan SR is formulated for slow release, so the medicine enters the bloodstream gradually rather than quickly.
• Peak levels: With SR preparations, peak blood levels generally occur later than immediate-release forms (timing varies by patient and dose).
• Metabolism: Verapamil is primarily metabolised in the liver. This is important for people with liver impairment and those taking medicines that affect liver enzymes.
• Elimination: The medicine and its metabolites are cleared mainly through the kidneys (with some contribution from other pathways).
• Half-life: Verapamil’s half-life varies between individuals and may be influenced by age and liver function.

Because verapamil undergoes liver metabolism and can interact with other medicines, blood levels may change when combined with certain drugs or when taken with certain foods (see “Food interactions” below).

Typical uses in Australia

Calan SR (verapamil) is used for cardiovascular conditions where slowing heart conduction and/or lowering blood pressure is beneficial. Common indications include:

• Hypertension (high blood pressure) – helps relax blood vessels.
• Angina (chest pain) – helps reduce cardiac workload and improve blood flow to the heart in appropriate patients.
• Some supraventricular arrhythmias – particularly rhythms that involve the AV node.

The exact choice of verapamil (and the SR formulation) depends on the specific diagnosis, heart rate/rhythm, co-existing conditions, and other medications.

Timing: when to take Calan SR

Timing can affect how consistently the medicine works during the day.

• Follow your dosing schedule exactly (for example, once daily or twice daily), as recommended by your healthcare professional.
• Take at the same times each day to maintain steadier levels.
• With or without food: Many patients can take verapamil SR with food or on an empty stomach, but grapefruit and alcohol guidance is important (see below).
• Swallow whole: SR tablets should not be crushed or chewed because that can change how the medicine is released.

If you miss a dose, do not take a double dose. Take the next dose at the usual time unless your healthcare professional advises otherwise.

Food interactions: what to know

Some foods and beverages can change verapamil levels and effects.

• Grapefruit and grapefruit juice: Grapefruit can increase verapamil levels by affecting liver enzymes, potentially raising the risk of side effects (such as dizziness, low blood pressure, or slow heart rate). It is generally recommended to avoid grapefruit products while taking verapamil.
• Alcohol with meals: Alcohol can add to the blood pressure-lowering and heart-rate-slowing effects (details below).
• General diet: There are no major universal food restrictions beyond grapefruit, but severe vomiting/diarrhoea can affect absorption and hydration and may change blood pressure regulation.

If you notice symptoms after dietary changes—such as new dizziness, faintness or unusually slow pulse—speak with your healthcare professional.

Alcohol and medicine interactions

Verapamil can lower blood pressure and slow heart rate. Alcohol can also affect blood pressure and circulation, which may increase the chance of side effects.

Alcohol

• Dizziness, light-headedness and fainting: The combination may increase these risks, especially when starting therapy or adjusting the dose.
• Reduced driving safety: Alcohol may make it harder to recognise dizziness early.
• Individual variability: Some people tolerate small amounts better than others; the safest approach is to discuss a personalised plan with your healthcare professional.

Common medicine interactions

Verapamil interacts with several medicines, mainly because of effects on heart conduction and because of liver enzyme interactions. Examples include:

• Other medicines that slow the heart (for example, some beta-blockers or digoxin): may increase risk of bradycardia (slow heart rate) or AV block.
• Medicines that affect heart rhythm (antiarrhythmics): may increase the risk of rhythm problems when combined.
• Medicines that increase verapamil levels (some antifungals, certain antibiotics, and other drugs affecting liver metabolism): can raise verapamil side effects.
• Medicines that reduce verapamil levels: may lessen its effect.
• Statins: Some cholesterol-lowering medicines may interact with verapamil and increase the risk of statin-related muscle effects; dose adjustments may be needed.
• Other antihypertensives: may lead to an additive blood pressure-lowering effect.
• Medicines for migraine, erectile dysfunction, or other conditions that influence blood vessels: may interact through blood pressure effects.
• Herbal products: Some supplements can affect heart rhythm or liver enzymes. Tell your healthcare professional about anything you take regularly.

Always provide a complete list of your medicines and supplements when starting or changing therapy. This includes over-the-counter medicines (including decongestants), as they can affect heart rate and blood pressure.

Indications: which conditions it treats

Calan SR is commonly prescribed for:

• High blood pressure (hypertension)
• Angina (to help prevent symptoms in suitable patients)
• Certain supraventricular tachycardias (depending on the specific rhythm and patient profile)

Whether verapamil is suitable depends on the specific heart rhythm diagnosis, your heart function, blood pressure, and other medicines. People with certain conduction disorders or severely reduced heart function may not be suitable.

Dosing: general guidance

Dosing is individualized. The following information is to help you understand typical dosing considerations, not to replace personalised instructions.

Important dosing principles

• Start low and adjust slowly: To reduce the risk of low blood pressure or slow heart rate, doses are often titrated gradually.
• Consider liver function: Because verapamil is metabolised in the liver, people with liver impairment may require different dosing and closer monitoring.
• Age and frailty: Older adults may be more sensitive to blood pressure and heart-rate changes.
• Heart rate monitoring: Dose adjustments may depend on pulse rate and symptoms (for example, dizziness or fainting).

How to take SR tablets safely

• Swallow whole with water; do not crush, split or chew.
• If your tablet has a score line, do not assume it can be split for SR release—only split if your product instructions explicitly permit it.
• Keep consistent timing; avoid sudden dose changes without advice.

If you’re unsure about your exact dosing schedule, check the pharmacy label or ask your pharmacist. Never stop verapamil suddenly unless advised.

Safety profile: who should take extra care?

Like all medicines, Calan SR can cause side effects. Many are mild and improve after dose adjustment, but some require urgent attention.

Common side effects

• Dizziness or light-headedness
• Headache
• Flushing
• Swelling (oedema), especially in the ankles/legs
• Constipation (a well-known effect of verapamil)
• Fatigue
• Nausea

More serious side effects (seek medical help promptly)

• Very slow heart rate, fainting, severe dizziness, or signs of heart block
• Worsening shortness of breath, unusual weight gain, or swelling that rapidly increases
• Chest pain that is new or significantly worse
• Allergic reaction (for example, rash, swelling of lips/face, difficulty breathing)
• Severe dizziness especially when standing

When urgent care may be needed

Go to the nearest emergency department or call emergency services if you experience symptoms such as fainting, severe chest pain, severe breathlessness, or symptoms suggesting a serious rhythm disturbance.

Caution in certain conditions

Extra caution (and close monitoring) may be needed if you have:

• Heart conduction problems (such as AV block)
• Very low heart rate
• Significant heart failure or reduced pumping function (depending on clinical judgement)
• Low blood pressure
• Liver disease
• Kidney disease (often still usable but may require monitoring)

Practical use tips for patients

• Check pulse and blood pressure if advised: Especially during dose changes.
• Stand up slowly: To reduce dizziness, especially in the morning or after sitting.
• Manage constipation early: Drink adequate fluids, maintain fibre intake, and discuss a suitable plan with your pharmacist if constipation occurs.
• Avoid grapefruit: To help prevent higher-than-expected verapamil levels.
• Keep a medication list: Include all prescriptions, over-the-counter products and supplements to reduce interaction risk.
• Don’t stop suddenly: Stopping verapamil without medical advice can worsen symptoms.
• Be cautious with driving or machinery: If you feel dizzy, wait until you feel stable.

What to do if you miss a dose

If you miss a dose:

• Take it as soon as you remember if it’s close to your scheduled time.
• If it’s near the time of the next dose, skip the missed dose.
• Do not take a double dose to make up for the missed tablet.

If you frequently miss doses or are unsure, ask a pharmacist for advice.

Alternative options

Treatment choices depend on your diagnosis. Alternatives may include other medicine classes or different calcium channel blockers. Examples (not exhaustive) include:

• Other calcium channel blockers (for example, different agents may be used depending on the condition)
• Beta-blockers for selected heart rhythm or angina situations
• Other antiarrhythmic or rate-control medications when appropriate
• Antihypertensives from other classes for blood pressure management

Your clinician will choose an alternative based on your specific heart rhythm, blood pressure, heart function, kidney/liver status and interaction risk.

Market and legal context in Australia (plain-English overview)

In Australia, medicines are regulated through the Therapeutic Goods Administration (TGA). Most cardiovascular medicines, including verapamil products used for heart conditions and hypertension, are subject to prescription and pharmacist oversight requirements.

Online pharmacies in Australia operate within Australian regulations, including identity checks, medicine supply rules, and pharmacist counselling where required. Availability may vary by brand and strength. Always ensure your product is an Australian-authorised supply and stored appropriately.

If you are purchasing or transferring care, keep in mind that formulations and brands may differ; confirm the exact strength and SR form with your pharmacy.

Recent guidance and monitoring considerations

While specific “recent” updates can vary by clinical setting, general modern guidance for verapamil use consistently emphasises:

• Careful assessment of interactions (particularly medicines that affect heart rate, conduction, or liver metabolism).
• Monitoring for bradycardia and blood pressure lowering, especially during dose initiation or titration.
• Appropriate use of SR formulations (swallow whole; avoid altering release characteristics).
• Patient awareness of warning signs (fainting, severe dizziness, worsening shortness of breath, or new chest pain).

If you have concerns or have started a new medicine recently (including antibiotics or antifungals), speak with your pharmacist to confirm there are no significant interactions.

Delivery and availability

Online pharmacies typically offer home delivery across Australia. Delivery timeframes depend on the pharmacy’s dispatch schedule and your location. Some products may be subject to stock availability and strength/pack size.

• Availability: Calan SR strengths and packs can vary. If your exact strength is unavailable, you may be offered a suitable alternative formulation or strength depending on what your clinician recommends.
• Packaging: Medicines are usually dispatched in original packaging with clear dosing information.
• Storage on arrival: Store at room temperature in a dry place, away from direct sunlight (follow the label instructions).
• Delivery privacy: Many pharmacies use discreet packaging.

If you need urgent supply due to missed doses, contact the pharmacy directly—some services may offer expedited delivery where available.

FAQ – Calan SR (Verapamil)

1. Is Calan SR the same as regular verapamil?

Calan SR is a slow‑release (SR) verapamil formulation. It releases medicine gradually, which helps maintain more consistent blood levels. Do not substitute SR with immediate-release without medical advice.

2. Can I crush or split Calan SR tablets?

Generally, SR tablets should be swallowed whole. Crushing or splitting can change the release pattern and may increase side effects or reduce effectiveness. If your tablet has specific instructions on the pack, follow those. When in doubt, ask a pharmacist.

3. How quickly will it work?

Some effects (such as changes in heart rate or blood pressure) may be noticed after starting, while full benefits for conditions like hypertension may take days to weeks. Your clinician may monitor you during dose changes.

4. What should I do if I feel dizzy after taking my dose?

Sit or lie down to reduce fall risk. Check your blood pressure and heart rate if you can. If dizziness is severe, you faint, or you have chest pain or worsening shortness of breath, seek urgent medical care.

5. Is it safe to drink alcohol while taking verapamil?

Alcohol can increase the risk of dizziness and low blood pressure. Moderate use may be acceptable for some people, but it’s safest to discuss your situation with a healthcare professional—especially if you’re new to therapy, adjusting dose, or already have low blood pressure.

6. Can I have grapefruit products?

It is generally recommended to avoid grapefruit and grapefruit juice because it may increase verapamil levels and side effects.

7. What medicines interact with verapamil?

Verapamil can interact with medicines that affect heart rhythm or slow the heart, and with medicines that alter liver metabolism (which can change verapamil levels). Always share your full medication list with your pharmacist, including over-the-counter products and supplements.

8. What side effect is most common?

Common side effects include dizziness, headache and constipation. Swelling in the ankles/legs can also occur. If side effects are troublesome or persistent, ask for advice—dose adjustment may help.

9. How do I manage constipation caused by verapamil?

Increase fluids where appropriate, maintain fibre intake, and consider gentle stool softening strategies. If constipation is significant or you have abdominal pain, seek medical advice. A pharmacist can recommend suitable options.

10. Can I stop Calan SR suddenly?

Do not stop verapamil suddenly without medical advice. Stopping may worsen symptoms such as blood pressure control or angina/rhythm stability. If you’re considering stopping, discuss a safe plan with your clinician.

11. Is Calan SR safe during pregnancy or breastfeeding?

Safety depends on individual circumstances. If you are pregnant, planning pregnancy, or breastfeeding, discuss risks and benefits with your healthcare professional before continuing or starting verapamil.

12. What should I do in case of overdose?

Overdose with heart medicines can be dangerous. If an overdose is suspected, seek urgent medical help immediately and contact emergency services or a poisons service (as appropriate in Australia).

Summary

Calan SR (verapamil SR) helps manage certain cardiovascular conditions by relaxing blood vessels and slowing heart conduction. Because it can affect heart rate and blood pressure—and because it has meaningful interactions—safe use depends on correct dosing, avoiding grapefruit, moderating alcohol, and checking interactions with all medicines and supplements. If you experience warning signs such as fainting, severe dizziness, chest pain, or worsening shortness of breath, seek urgent medical care.