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Antiarrhythmics help control irregular heart rhythms such as atrial fibrillation (AF), supraventricular tachycardia (SVT) or ventricular tachycardia (VT). Find out how antiarrhythmics work and their side effects.

Types of antiarrhythmic medication

  • amiodarone, also called Aratac, Cordarone X
  • digoxin, also called Lanoxin, Lanoxin PG
  • flecainide, also called Tambocor CR, Felcainide (Teva), Arrow-Flecainide
  • propafenone, also called Rytmonorm
  • beta blockers
  • calcium channel blockers

How do antiarrhythmics work?

Antiarrhythmics help manage electrical problems in your heart that cause irregular heart rhythms, like atrial fibrillation or tachycardias (fast heartbeats).

Side effects

Side effects are common with antiarrhythmic medication, so it’s important to take note of any changes and talk about them with your health professionals. Often, the side effects are more noticeable when you start the medication, but these may reduce over time.

Your doctor may also adjust your medication dosage so it works best for you.

Common side effects caused by antiarrhythmics include:

  • possible issues with your liver, kidneys, thyroid or lungs (these will be monitored by your health professional)
  • tiredness
  • nausea (feeling sick) 
  • shortness of breath (if this gets so bad that you feel unsafe, seek medical attention immediately).

Ring 111 if you have any of the following:

  • severe chest pain
  • severe headache
  • acute shortness of breath (your breathing is so difficult that you feel unsafe)
  • swelling of your mouth, lips or tongue, as this could be an allergic reaction.

Amiodarone also causes sensitivity to sunlight and skin changes are common. Sun protection is important if you're taking this medication.

Talk to your doctor if your side effects are worrying you. Don’t stop taking your medication without talking to your doctor first. The benefits usually outweigh the side effects. It may take a while for the medication to work.

What checks do I need?

You may need regular blood tests to check on your liver, thyroid, lung and kidney function.

What happens if I miss a dose?

If you forget to take a dose, take it immediately, then continue as normal the following day. However, if it’s almost time for the next dose, skip the missed dose and continue as normal. 

Do NOT take a double dose.

What else do I need to know when taking antiarrhythmics?

Tell your health professionals if you're taking any:

  • supplements
  • natural medicines
  • vitamins 
  • alternative therapies. 

These can sometimes make your heart medications less effective. 

Avoid eating grapefruit or drinking grapefruit juice when you're taking antiarrhythmics because it changes the way your body reacts to the medication.

Related treatments and conditions

Atrial fibrillation


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