Antiarrhythmic medications work by helping to stabilise electrical impulses within the heart.

Medication used for this will differ for each person, their symptoms and their heart function. You might take your medication as and when you need it ('pill in the pocket') or we may tell you to take it on a regular basis. We may also look at combining medications so that we keep your heart rate/rhythm under control.

You must make sure to continue your anticoagulation medication regardless of your treatment strategy for rate or rhythm control. This is so you can reduce your risk of stroke.

These are the common medications we use to treat atrial fibrillation.

Beta-blockers (bisoprolol, atenolol, carvedilol)

Beta blockers work by blocking the effects of adrenaline and other related hormones on the heart to slow your heart rate down.

These treat AF and also other heart conditions, such as angina and following a heart attack. There are many different types of beta blockers, but they all end with "ol".

Some beta blockers are better suited to treat heart conditions, such as carvedilol, bisoprolol, atenolol and metoprolol. Others can be used such as propranolol but are more often used to treat other conditions, such as migraines and tremors. Sotalol has a beta blocker component to it but also works as a class III anti-arrhythmic medication.

Beta blockers are usually the first line for treatment of AF regardless of it being for a rhythm or rate control strategy. We may also use them in combination with other anti-arrhythmic drugs such as:

  • calcium channel blockers (diltiazem/verapamil)

  • amiodarone

  • flecainide

  • digoxin

  • dronedarone. 


The dose you will need to take will depend on what kind of beta blocker we prescribe. Bisoprolol is the most common and is taken once a day, with doses between 2.5mg and 10mg.

You should not suddenly stop taking your beta blockers unless you have been told by your healthcare professional. This is because you may experience your arrhythmia symptoms again if you do.


To make sure you are on the correct dose, we may check your heart rate and/or do an ECG after you have started taking the beta blocker. This is usually done one to two weeks after starting the medication.

Side effects


The most common side effect that people experience when taking beta blockers is fatigue and tiredness. This can occur in around one in 10 patients. Sometimes people tolerate one beta blocker better than another and sometimes they are only able to tolerate low doses.


Beta-blockers sometimes affect the lungs and cause breathlessness. This can happen to people to have pre-existing lung conditions, including asthma or chronic obstructive pulmonary disease (COPD).

Your doctor may want you to try a small dose of the beta blocker at first to make sure that you can tolerate it. If you have a pre-existing lung condition we may suggest you check your peak flow more often, to make there is no deterioration in your breathing.

If you do not have an underlying lung condition, it is unlikely that you would get breathlessness from beta blockers. But if you do start to experience breathlessness, you must get medical help.


As beta-blockers reduce your heart rate and blood pressure they can sometimes make you feel dizzy and lightheaded. If you start to struggle with this, seek medical help.

Cold hands and feet

Beta blockers can affect the circulation and make your hands and feet cold. In cold weather, wrap up warm, wear gloves and an extra pair of socks if you need to.

For some people, they experience a temporary loss of circulation in their finger and toes, making them white and painful. This is a condition known as Raynaud's phenomenon and is a sign that you should stop taking your beta blockers.

Calcium channel blocker diltiazem/verapamil)

Calcium channel blockers can be used as part of a rate or rhythm control strategy for AF.

There are two types of calcium channel blockers, dihydropyridines and non-dihydropyridines. Dihydropyridines such as amlodipine and nifedipine control blood pressure or angina. Non-dihydropyridines such as diltiazem and verapamil can also control blood pressure and angina and be used as part of a rate and rhythm control as well.

Diltiazem and verapamil work by reducing the movement of calcium into the AV-node and in the arteries and veins. This causes the force and rate of the heart's contractions to decrease. This relaxes the arteries and then reduces blood pressure (BP). They can be used on their own or with other anti-arrhythmic drugs to enhance their effects.


You would normally start on a low dose of these and the increase them if you need to.

This usually means starting diltiazem at a dose of either 120mg once a day or 90mg twice a day. With verapamil, the starting dose is 120mg once a day or a split dose of either 40mg twice or three times a day. Your starting dose will depend on your heart rate and blood pressure. Different preparations of medications will have different names.

jFor verapamil, you may have Securon SR, Half Securon SR or Univer, and for diltiazem, you may have Tildiem retard, Dilzem, Adizem XL or Adizem SR. You need to keep taking the brand of medication as the different preparations will have different effects. If you change brands, you may find that your arrhythmia symptoms return, but check with your pharmacist if you think you have the wrong preparation.  


This will usually be done one to two weeks after starting the medication. When you start taking a calcium channel blocker, we may check your heart rate and/or do an ECG to make sure the dosage it right for you. We will do this one to two weeks after you start your medication.

Side effects

The most common side effects patients who take this kind of medication have are feeling flushed and light-headed. You may also have headaches and swollen ankles.


This medication can cause a drop in BP for some patients, meaning they experience some light-headedness or dizziness.

Ankle swelling 

You may find that your ankles become swollen with this medication. This is because they widen your arteries and veins, but this should stop once you have finished taking the medication.

Heart failure

If you know that you have severe heart failure (known as left ventricular impairment) you should not use verapamil or diltiazem. These medications can reduce the contraction of the heart, which is not safe for those with severe heart failure. If you have mild or moderate heart failure you may be given diltiazem if other antiarrhythmics are not suitable for you.

If you notice any of the following you should contact your GP as soon as possible: 

  • Any difficulties breathing, new breathlessness on exertion
  • Severe ankle swelling


Digoxin is a medication extracted from foxglove plants and is used to treat AF.

It works by slowing the electrical impulses through the AV-node, helping to control how fast the ventricles contract.

Digoxin works best when you are resting, but for active people, it doesn't work as well on its own to control your heart rate whilst you exercise. We may use it in combination with other antiarrhythmics like beta blockers, calcium channel blockers or amiodarone. 

For those who have severe heart failure, this medication can help your heart beat stronger and improve the symptoms of heart failure. 


You would take this medication once a day but may need to take a higher 'loading' dose initially. This can be taken either as a tablet or via intravenous injection. 

The dose will be between 62.5 to 250mcg daily, but this will depend on your symptoms, heart and kidney function. 


You would only need your Digoxin intake monitored if your doctor feels that the dosage is too low or if you are having side effects. Side effects can also be related to your dosage being too high. 

If we need to, we can do a blood test to check the Digoxin levels in the bloodstream. We would check the levels around six to ten hours after you have taken the medication, so if you take it in the morning, we would check the levels in the afternoon. We may also do periodic checks on your kidney function, as digoxin is not removed from the body as well if you have impaired kidney function. 

Side effects

This medication is usually well tolerated by those taking it but if your dose is too high, you may start to show signs of toxicity. This includes: 

  • loss of appetite
  • nausea
  • vomiting
  • diarrhoea
  • blurred vision
  • visual disturbances (yellow-green halos around people or objects, some have described these as auras)
  • confusion 
  • drowsiness
  • dizziness

If you think that your digoxin is causing problems, get medical attention for it. 

'Pill in the pocket'

This strategy for medication means that you would take a tablet as soon as you realise that you are having an AF episode. If you have been diagnosed with paroxysmal AF, your episodes may be infrequent, so you be told to use the 'pill-in-the-pocket' approach. We will tell you to take a dose of your anti-arrhythmic medication when you have an AF episode to help stop it. These will include either flecainide, a beta blocker or possibly a calcium channel blocker. 

This approach works well if you are able to identify when an episode starts. It also works well if you respond well to the medication you have been told to take, and know how much to take and when. 

If your symptoms do not improve and you feel very unwell, you should call an ambulance.

If you have an AF episode that lasts for more than 48 hours, you should see your GP or get advice from your arrhythmia specialist. This may be because your treatment needs to change. 

If you are unsure when you need to take your medication, speak to your GP or your arrhythmia specialist pharmacist/nurse specialist.

If this approach does not work for you, or your AF episodes happen more frequently, we may tell you to start taking the medication daily. 

There are a few antiarrhythmics which can be used for the 'pill-in-the-pocket' approach or used regularly. Which medication you use will depend on any underlying heart disease, such as coronary heart disease, heart failure and hypertension. It will also depend on the side effects and how effective the drug may be. 


Flecainide is a sodium channel-blocking drug, which slows the conduction (carrying the electrical impulses) within the heart. Its main purpose is to act on the atria and also slow conduction through the AV-node.

It is very effective in treating episodes of AF and is often better tolerated than some of the other anti-arrhythmic medications. Its effect is more obvious with faster heart rates, which makes it very useful to control fast episodes of AF. 

This drug is only given to people who have a normal functioning heart.


When you start taking flecainide, you will start on a low dose (50mg twice a day), with possibly going up to 200mg twice a day. this will depend on your symptoms and your ECG. 

If you are prescribed flecainide, you may also have to take a beta block or calcium channel blocker. This is to protect the lower chambers of the heart (ventricles) from contracting too quickly. 


Once you start taking flecainide you will need to have regular ECGs. Flecainide slows the conduction in the heart and this change will be shown on your ECG. But we will want to make sure that the conduction has not slowed down too much. You will normally have an ECG about one week after starting flecainide and then after each increase in dosage. 

Side effects

The most common side effect of flecainide is visual disturbances. This is usually reported as blurred vision. Less common side effects include gastrointestinal symptoms (such as nausea) and dizziness. 

Flecainide can also cause arrhythmias, so this is why it is only given to patients that have a normal functioning heart.


Sotalol is a mixture of a beta-blocker and an anti-arrhythmic. In low doses, it acts like a beta blocker. With higher doses, it acts like an anti-arrhythmic by blocking potassium channels and slowing conduction in the heart.


You will start on a low dose (40mg twice a day) and can go up to 160mg twice a day. This will depend on your symptoms and your ECG.


When you start taking sotalol you will need to have regular ECGs. This is because higher doses of sotalol slow down conduction in the heart, which will be reflected in your ECG. We need to check that the conduction has not slowed down too much.

It is especially important that we check this when your heart is in sinus rhythm.

Sotalol can also be pro-arrhythmic, which causes arrhythmias. If we see certain changes on your ECG you may tell you to reduce or stop your sotalol.

You will usually have an ECG about one week after starting sotalol and after each dose increase.

Side effects

The most common side effect with sotalol is bradycardia (when the heart beats at a slow rate, usually less than 60 beats per minute). 

Other side effects, which are associated with beta blockers, include:

  • fatigue or tiredness
  • cold extremities (cold hands and feet)
  • exacerbation of asthma 
  • light-headedness. 


This drug works in a similar way to sotalol by blocking potassium channels and slowing conduction within the heart.

Amiodarone is very effective at maintaining sinus (normal) rhythm. We would suggest this drug for patients with structural heart disease or who have tried other AF medications without success.

Even though it is a powerful and effective drug, it does have side effects so we may suggest you take it for a short period of time.


You will start this medication either with a tablet or by intravenous injection over 24 hours. This will depend on the severity of your symptoms.

Because of the structure of amiodarone, it takes a long time (weeks to months) for levels of the drug to build up in the body. We will start with getting you to take 200mg three times a day for one week. This will then be reduced to twice a day for one week, and then one a day afterwards.

Side effects

Although generally well tolerated, amiodarone can cause some side effects.


Amiodarone can make the skin have a greyish/blue look when it comes into contact with sunlight. Your skin may also be more sensitive to getting sunburnt, so it is important to wear plenty of sunblock and protective clothing. As amiodarone remains in the body for a long time, you may need to continue using sunblock for a few months after you stop taking the drug.


The thyroid gland produces a hormone which controls the body’s metabolism. Amiodarone can affect this gland making it both overactive or underactive. An overactive thyroid happens to about two per cent of patients and an underactive thyroid happens to about six per cent of patients. Your doctor will take regular blood tests to check if either of these has developed.

If you experience symptoms of extreme tiredness or restlessness, contact your GP to discuss this further. Your doctor will arrange for you to have blood tests if you have not already had them. Both underactive and overactive thyroids can be treated with medications. If you develop an overactive thyroid, we may tell you to stop taking amiodarone.


Small deposits can form on the cornea of the eye (the clear surface that covers the pupil, iris and white of the eye). These deposits are not harmful, but you may notice the effects when looking at bright lights at night time, such as when you are driving.

Around one in ten people taking amiodarone will notice a bluish halo around their vision but this is not harmful.


Amiodarone can cause problems with thickening (fibrosis) of the lungs, which may be irreversible. The risk of this occurring increases if you have been on the medication for a long time. If you experience shortness of breath, see your GP as soon as you can.


Amiodarone can cause problems with the function of the liver in rare cases. Your doctor will perform regular blood tests to check that your liver function is normal. If you experience jaundice (yellowing of the skin) or new nausea and vomiting, see your GP as soon as possible.

Other side effects

When you first start taking amiodarone, you may experience some nausea and vomiting. This should settle within a few days, but if you continue to have problems, contact your GP. You may also get some taste disturbances, like a metallic taste in your mouth. This is not uncommon for people taking amiodarone, but if you are concerned, see your GP.


When you start taking amiodarone, you will have a blood test to check your liver and thyroid function. You will also have a chest X-ray if you have not had one recently. Your GP will then recheck your liver and thyroid function every six months.

Amiodarone can interact with many medications and herbal medicines. So it is very important that your GP and pharmacist are aware of all the medicines you are taking (including herbal products).

We may recommend reducing your statin dose and digoxin intake. If you are taking warfarin, amiodarone will cause your INR to increase, so we will reduce your warfarin dose.

If you notice any of the following you should contact your GP as soon as possible:

  • Any difficulties breathing, or if you develop an unexplained cough.
  • Extreme tiredness or restlessness.
  • Jaundice (any yellowing of your skin or the whites of your eyes). These could be signs of a problem developing in your liver.
  • A severe skin rash. This could be a sign of an allergic reaction.


Dronedarone has a similar structure to amiodarone but is not considered to be as effective as amiodarone. The advantage of dronedarone is that it seems to be better tolerated and has fewer side effects.

We would only recommend someone to take this drug if other antiarrhythmics are unsuitable for them or if they cannot tolerate them. It is also only used by patient who paroxysmal or persistent AF to help maintain sinus rhythm.


The dose of dronedarone is 400mg twice a day and you will need to take it with food.


There are some reports of this drug causing liver damage, so when you first start taking it you have a blood test to check your liver function. This will happen every month for the first six months of your treatment, then at nine months. You will then have another at 12 months and then at certain intervals after that.

You will also have a blood test seven to ten days after starting the drug to check your kidney function. You will also have an ECG at least every six months. If your ECG shows that you have remained in persistent AF, this indicates that the medication is not working as it should and you will need to stop taking it.

Side effects

The most common side effects that people experience are:

  • gastrointestinal disturbances, such as nausea, vomiting, diarrhoea or abdominal discomfort
  • skin rashes
  • bradycardia
  • changes in your ECG (although this is rare). 

Side effects should stop within the first two weeks of starting dronedarone. But for some patients, we will tell them to stop taking because of the side effects.

You should contact your GP if you experience any of the following:

  • Any difficulties breathing
  • Swollen ankles
  • New onset abdominal pain
  • Jaundice (any yellowing of your skin or the whites of your eyes)

These could be signs of a problem developing in your liver.

Dronedarone can interact with many medications and herbal medicines. So you must make your GP and pharmacist aware of all the medicines you are taking (including herbal products).

We may tell you to reduce your statin, verapamil/diltiazem or digoxin dose as dronedarone interacts with them. It can also increase the circulating levels of these drugs in the body.

You should also avoid grapefruit whilst taking dronedarone.

Getting further supplies of dronedarone

You may find that your GP is unable to continue to provide you with further supplies of dronedarone tablets. This is due to funding restrictions by the Clinical Commissioning Groups (CCGs).

Your GP may prescribe dronedarone for you if they have an agreement from the hospital, known as a shared care document. This details the responsibilities of both the GP and the hospital.

If you are having difficulties obtaining a regular supply of your tablets, please contact Sally Manning, senior arrhythmia pharmacist.

Atrial fibrillation is an abnormal heart rhythm. It is the most common heart rhythm disorder in the UK.

Meet the team

The arrhythmia team includes: 

  • EP consultants
  • clinical nurse specialists
  • an arrhythmia pharmacist 
  • catheter laboratory technicians. 


Dr Jonathan Clague
Dr Sabine Ernst 
Dr John Foran
Dr Wajid Hussain 
Dr Julian Jarman
Dr David Jones
Dr Vias Markides
Dr Tushar Salukhe
Dr Jan Till 
Dr Tom Wong

Clinical nurse specialists

Natalie Crump 
Sue King
Sarah Plowright 
Alex Wise 

Arrhythmia pharmacist

Sally Manning 
Zainab Khanbhai

Contact the team

Harefield Hospital: 01895 828979
Royal Brompton Hospital: 020 7351 8364