Anti-arrhythmic medicines and what they do

About anti-arrhythmic medicines

What are anti-arrhythmic medicines?

Anti-arrhythmic medicines are used to treat abnormal heart rhythms (arrhythmias). Abnormal heart rhythms mean your heart is beating too fast, too slow or it misses beats.

There is an electrical system in your heart that sends out electrical impulses to help it to beat regularly and in time. When the electrical impulses are not working properly it causes an abnormal heart rhythm.

You may be given anti-arrhythmic medicines if you have a condition that affects your heart rhythm, such as:

• atrial fibrillation
• atrial flutter
• supraventricular tachycardia
• tachybrady syndrome (sick sinus syndrome)
• heart block.

In some cases, anti-arrhythmic medicines may not be suitable, for example if you have:

• heart failure
• heart muscle damage from a heart attack
• been diagnosed with a life-threatening arrhythmia.

Your doctor will talk to you about other treatments options.

How do anti-arrhythmic medicines work?

Anti-arrhythmic medicines help your heart by:

• stopping any extra electrical impulses in your heart
• preventing any abnormally fast impulses in your heart
• slowing down your heart rate during the abnormal heart rhythm to make it more manageable.

There are different types of anti-arrhythmic medicines, and they work in different ways.

Types of anti-arrhythmic medicines

What are the different types of anti-arrhythmic medicines?

There are 4 main types (classes) of anti-arrhythmic medicines:

1. Sodium channel blockers – these medicines block sodium and help slow down the electrical impulses in your heart. Examples include disopyramide, flecainide and propafenone.
2. Beta blockers – these medicines help block stress hormones, like adrenaline and noradrenaline, helping the heart beat slower and steadier. Examples include atenolol and metoprolol.
3. Potassium channel blockers – these medicines block potassium and help slow down the electrical impulses in your heart. Examples include amiodarone, dronedarone and sotalol.
4. Rate-limiting calcium channel blockers – these medicines reduce the amount of calcium entering the cells of your heart and blood vessels. This helps slow down and regulate your heart rate. Examples include verapamil and diltiazem.

There are also other types of anti-arrhythmic medicines, such as adenosine and digoxin. They're used to treat supraventricular tachycardia (SVT).

Side effects

What are the side effects?

Side effects from some anti-arrhythmic medicines may include:

• stomach pain
• feeling more tired than usual (fatigue)
• feeling dizzy or faint
• feeling sick (nausea)
• pounding or fluttering in your chest (palpitations)
• sensitivity to bright light
• cold hands and feet
• overactive or underactive thyroid
• trouble getting an erection
• low blood pressure.

In some cases, anti-arrhythmic medicines can lead to other abnormal heart rhythms. You’ll have regular appointments to have your heart checked.

All medicines have potential side effects, but most people will not experience side effects.

If you’ve started taking anti-arrhythmic medicines recently it’s worth bearing in mind that side effects with any new medicine often improve over time or even disappear.

When should I get help?

Talk to your doctor if you’re having side effects. They can help you manage them or look at other options with you.

Your heart will be checked regularly to make sure the medicine is working and you do not have any side effects.

If the medicine is no longer working, your doctor may recommend a different type of anti-arrhythmic medicine or another type of treatment like:

• anticoagulants
• catheter ablation
• cardioversion
• an implantable cardioverter defibrillator (ICD)
• a pacemaker.

It’s important not to stop taking your medicine without speaking to a healthcare professional first.

How and when to take them

How do I take this medicine?

Most anti-arrhythmic medicines are tablets you swallow. They’re either taken:

• As a “pill in the pocket” – where you take the medicine when you’re having an abnormal heart rhythm.
• Regularly – usually taken once a day, at the same time every day.

In some cases, you may be given an anti-arrhythmic injection.

Your doctor will give you more information about the type of medicines they’re giving you and how often you should take it.

What should I do if I forget to take my medicine?

If you forget to take your medicine and:

• It's only a short time after your usual dose, take it as soon as you remember. Then take your next dose at the usual time.  
• It’s nearly time for your next dose, do not take the one you missed. Wait and take your next dose at the usual time. 

How long do I take it for?

Most people will need to take these medicines long-term to help treat their condition.

Things to avoid if you’re taking anti-arrhythmic medicines

There are certain foods and medicines you may need to limit or avoid if you’re taking anti-arrhythmic medicines. This is because they can stop your medicine from working properly.

Depending on the medicine you’re taking, this may include:

• grapefruit and grapefruit juice
• St John’s wort.

Check with your doctor or pharmacist to find out if you need to avoid any foods or medicines while taking anti-arrhythmic medicines.

If you’re pregnant or planning to get pregnant speak to your doctor about the medicines you’re taking.

Get help with anti-arrhythmic medicines

• Our cardiac nurses can help answer your questions on anti-arrhythmic medicines. Call, email or live chat with them on our Heart Helpline.
• Check if you can get free prescriptions or help paying for your prescriptions.
• Talk to other people with abnormal heart rhythms and get support in our online community.