An antiarrhythmic (heart-rhythm medicine)
Amiodarone
A powerful medicine for serious abnormal heart rhythms — very effective, but it builds up in the body and needs regular checks of the thyroid, liver and lungs.
What is Amiodarone?
Amiodarone is an antiarrhythmic used for troublesome or dangerous abnormal heart rhythms, such as some cases of atrial fibrillation and life-threatening ventricular arrhythmias. It is highly effective but very long-acting and stored in body tissues, so it can affect the thyroid, lungs, liver, eyes and skin over time and requires regular monitoring. It is usually a specialist-guided treatment.
Education and reference only. This is a plain-language guide to Amiodarone — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Amiodarone is one of the most effective medicines available for controlling abnormal heart rhythms, and is used when a rhythm is difficult to control or potentially dangerous — for example some cases of atrial fibrillation, or life-threatening ventricular arrhythmias. Its power comes with a trade-off: it is extremely long-acting and accumulates throughout the body, so it can cause side effects in several organs and needs careful, ongoing monitoring. For that reason it is usually started and supervised by a heart specialist, and reserved for situations where other options are unsuitable.
How it works
Amiodarone acts on the electrical signalling of the heart in several ways, mainly by lengthening the time each heart cell needs before it can fire again (prolonging the "action potential"). This stabilises the rhythm and makes chaotic or fast abnormal rhythms less likely to take hold. It has an exceptionally long half-life — it can remain in the body for weeks to months after stopping — which is why its effects, and its side effects, build up slowly and persist for a long time.
What it treats
Conditions Amiodarone is used for
Practical use
How to take Amiodarone
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it exactly as directed; when starting, a higher "loading" schedule is often used for a while before settling to a lower maintenance amount.
- Protect your skin from the sun with high-factor sunscreen and clothing, as amiodarone makes the skin much more sensitive to sunlight.
- Avoid grapefruit juice, which can raise amiodarone levels.
- Do not stop suddenly without advice, and remember its effects and interactions persist for weeks after stopping because it clears so slowly.
- Report a new or worsening cough or breathlessness, marked tiredness, or symptoms of thyroid trouble promptly.
Weighing it up
Advantages & disadvantages of Amiodarone
Advantages
- Highly effective, including for rhythms that have not responded to other medicines.
- Can be used in people with heart failure where some other antiarrhythmics are unsafe.
- Available as both a tablet and an injection for emergencies.
Disadvantages
- Wide range of potentially serious side effects (thyroid, lungs, liver, eyes, skin) needing regular monitoring.
- Extremely long half-life — effects and interactions last weeks to months after stopping.
- Interacts with many medicines, notably warfarin and digoxin, whose effects it increases.
Practical use
Good to know
Because amiodarone stores in the body's tissues, its side effects are unusual among heart medicines: it can make the skin very sensitive to sunlight (and, rarely, turn it a slate-grey colour), leave harmless deposits in the eyes, and — most importantly — disturb the thyroid (causing either an under- or over-active thyroid) and, less often, affect the lungs and liver. This is why people on it have regular blood tests and periodic checks. Its long half-life also means interactions and effects continue for weeks after it is stopped. Contact your doctor promptly if you develop a new cough or breathlessness, which can rarely signal a lung problem.
Who should not take it / use with caution
- People with certain thyroid disorders, or particular slow heart rhythms / heart-block unless they have a pacemaker.
- People with a known sensitivity to iodine (amiodarone contains iodine) and, with caution, those with lung or liver disease.
- Pregnancy and breastfeeding, except where a specialist judges it essential.
Monitoring
- Thyroid function tests (before starting and regularly)
- Liver function tests (before starting and regularly)
- Chest X-ray at baseline and lung symptoms; periodic eye checks; heart rhythm (ECG) and potassium
Side effects
- Common: increased skin sensitivity to sunlight; harmless tiny deposits in the front of the eye (rarely affecting vision); nausea and taste changes.
- Important: thyroid problems (under- or over-active), which is why thyroid blood tests are done regularly; less commonly liver disturbance.
- Serious but less common: lung inflammation or scarring (report new cough or breathlessness); a slate-grey skin discolouration with long use; nerve or balance problems — all should be reviewed promptly.
Key interactions
- Increases the effect of warfarin (raising bleeding risk — the INR is watched closely) and of digoxin (raising the risk of digoxin toxicity).
- Adds to the effect of other medicines that slow the heart (such as beta-blockers, verapamil and diltiazem) and those that can affect the heart's electrical "QT" interval.
- Grapefruit juice raises its levels; it also affects statins (increasing muscle side-effect risk) and several other drugs — new medicines should be checked.
Available as: Tablets; also an injection used in hospital for emergencies.
Answers
Amiodarone: frequently asked questions
Why do I need so many blood tests on amiodarone?
Because amiodarone builds up in the body and can affect the thyroid and liver, regular blood tests catch any problem early, while it is still easily managed. Thyroid and liver tests are usually done before starting and every few months, along with checks of the lungs and eyes over time.
Why must I stay out of strong sun?
Amiodarone makes the skin much more sensitive to sunlight, so you can burn easily. Use a high-factor sunscreen, cover up, and avoid strong midday sun — this greatly reduces the risk of a reaction and of a rare longer-term skin discolouration.
How long does amiodarone stay in my body after stopping?
A long time — often weeks to several months — because it is stored in body tissues and cleared very slowly. This means its effects, and its interactions with other medicines, can continue for a while after the last dose, so tell any prescriber that you have recently taken it.
Can amiodarone affect my warfarin or digoxin?
Yes. Amiodarone increases the effect of both, raising the risk of bleeding with warfarin and of toxicity with digoxin. If you take either, your doses are usually reduced and you are monitored more closely when amiodarone is started or stopped.
Authoritative sources
- BNF: Amiodarone hydrochloride.
- electronic Medicines Compendium (SmPC): Amiodarone (Cordarone X).
- NICE CKS: Atrial fibrillation.
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