Amiodarone: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on July 26, 2023.

1. How it works

• Amiodarone may be used to treat and prevent abnormal rhythms of the heart (arrhythmias).
• Experts are not sure exactly how amiodarone works but believe it either affects receptors involved in electrical conduction or the length of time between electrical impulses in a cell.
• Amiodarone belongs to the class of medicines known as antiarrhythmics.

2. Upsides

• Recommended ONLY for the treatment of life-threatening recurrent ventricular fibrillation and recurrent hemodynamically unstable ventricular tachycardia in people who have not responded to or are intolerant of other antiarrhythmics.
• Available as an oral tablet and in an injectable form. Use the lowest effective dose.
• Generic amiodarone is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• Tiredness, tremor and involuntary movements, poor coordination and gait, nausea, vomiting, constipation, weight loss, elevation of liver enzymes, abnormalities in thyroid function tests, eye conditions that impair vision, peripheral neuropathy (pins and needles in the hands and feet), hyper or hypothyroidism (always suspect hyperthyroidism if a new arrhythmia occurs). Some side effects such as pulmonary fibrosis, liver-enzyme elevations, corneal deposits, and facial pigmentation, peripheral neuropathy, gastrointestinal and central nervous system effects are more likely at higher dosages.
• May cause pulmonary toxicity; symptoms include a cough and progressive shortness of breath.
• Amiodarone can significantly reduce a person's heart rate and may cause heart block (a slowing of electrical impulses within the heart). On rare occasions (2-5% of patients), amiodarone may worsen the arrhythmia being treated.
• Amiodarone is usually initiated in a hospital because it has been associated with life-threatening side effects. There is no evidence that treatment with amiodarone favorably influences survival.
• There is a wide variation in the way people eliminate amiodarone from their bodies and finding the right dosage of amiodarone for each individual may take some time. Some people may require blood level monitoring. It may be difficult to assess the effectiveness of amiodarone without further medical testing.
• Significant, potentially fatal toxicities and side effects associated with amiodarone usage include pneumonitis (inflammation of the alveoli in the lungs). In one study, this affected 10-17% of participants prescribed 400 mg/day of amiodarone. Reports indicate that pulmonary (lung) toxicity is fatal in 1 in 10 people.
• May also cause liver damage. This is usually mild but occasionally may be fatal.
• Not suitable for people with certain heart conditions (cardiogenic shock, AV block) and several other medical conditions.
• Avoid during pregnancy. Several fetal adverse effects have been associated with amiodarone such as hyper and hypothyroidism, neonatal bradycardia, QT prolongation, and neurodevelopmental abnormalities. Amiodarone and its metabolite DEA crosses into breastmilk and there have been cases of bradycardia and hypothyroidism in infants. Breastfeeding is not recommended. Amiodarone may also reduce male and female fertility.
• May interact with numerous drugs including antivirals, antidepressants, other heart medications, and warfarin. For a full list of interactions see here.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Amiodarone should ONLY be used in the treatment of life-threatening ventricular arrhythmias that have not responded to other treatments. Amiodarone does not appear to increase life expectancy and can be difficult to manage, with a high risk of potentially fatal toxicities. Every effort should be made to use alternative agents first.

5. Tips

• Take dosage exactly as directed; however, do not hesitate to call your doctor if you develop worrying side effects. Do not increase dosage without your doctor's consult as the lowest effective dosage should always be used.
• Avoid grapefruit juice and grapefruit products.
• May increase a person's sensitivity to the sun so avoid sunlight and indoor tanning beds whenever possible. Always use sunblock and wear a hat, sunglasses, and clothes that cover your skin if outdoor exposure is unavoidable. Talk to your doctor if you unintentionally get sunburnt.
• Long-term treatment may cause blue-gray discoloration of exposed skin. The risk may be increased in people of fair complexion, with excessive sun exposure, higher dosages, or longer duration of treatment.
• Contact your doctor urgently if you experience shortness of breath, coughing, chest pain, blood in your sputum, nausea or vomiting, brown or dark-colored urine, extreme tiredness, yellowing of your skin or the whites of your eyes, abdominal pain, disturbances to your heartbeat, swelling of your neck (goiter), or tremor.
• Amiodarone may make your eyes dry and you may need to relieve the dryness with over-the-counter lubricating eye drops. Call your doctor immediately if you experience halos around objects, blurred vision, or sensitivity to light. People taking amiodarone are not deemed suitable for corneal refractive laser eye surgery.
• If you are a woman of childbearing age you should use adequate contraception to ensure you do not become pregnant while taking amiodarone. Tell your doctor if you inadvertently become pregnant. Breastfeeding is not recommended during amiodarone treatment.

6. Response and effectiveness

• Amiodarone is absorbed slowly and maximum concentrations are reached three to seven hours after oral administration. Some effects may be seen after two to three days; however, it normally takes between one and three weeks of regular dosing for the full effects of amiodarone to be seen, even with a loading dose.
• The effects of amiodarone may continue to increase for several weeks until a plateau is reached.
• The relationship between the concentration of amiodarone and its effects is not well established, although generally 1 to 2.5 mg/L is suggested as the ideal range for amiodarone blood levels. Levels below this range are more likely to be associated with ineffectiveness, and levels above this range are likely to be associated with toxicity and increased side effects.
• Amiodarone has a very long half-life (this is the time it takes for 50% of a dose of amiodarone to be eliminated by the body) of 15 to 142 days. It also has an active metabolite, desethylamiodarone that has a half-life of 75 days. Potentially it may take weeks to months for amiodarone to be totally cleared from the body. This means side effects and interactions may persist even on amiodarone discontinuation.

7. Interactions

Medicines that interact with amiodarone may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with amiodarone. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with amiodarone include:

• alpha-blockers, such as prazosin
• anticonvulsants, such as carbamazepine, phenytoin, or phenobarbital
• antidepressants, such as nefazodone
• antifungal agents, such as itraconazole and ketoconazole
• antipsychotic agents, such as cyclophosphamide, thioridazine, or clozapine
• aprepitant
• barbiturates
• beta-blockers, such as atenolol, labetalol, or metoprolol
• bupropion
• chloroquine
• clopidogrel
• cyclosporin
• dabigatran
• digoxin
• dofetilide
• doxepin
• duloxetine
• HIV medications, such as atazanavir, darunavir, or ritonavir
• levodopa
• lidocaine
• loratadine
• lovastatin
• medications that prolong the QT interval such as azithromycin, clarithromycin, or pimozide
• medications that slow the heart rate, such as calcium channel blockers
• mifepristone
• other medications that inhibit or induce CYP2D6, CYP2C8, or CYP3A4, such as fluoxetine, duloxetine, clarithromycin, erythromycin, or glucocorticoids
• pholcodine
• red yeast rice
• rifampin
• quinidine
• simvastatin
• warfarin.

Note that this list is not all-inclusive and includes only common medications that may interact with amiodarone. You should refer to the prescribing information for amiodarone for a complete list of interactions.

References

• Amiodarone. Updated 07/2023. Cardinal Health 107, LLC. https://www.drugs.com/pro/amiodarone.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use amiodarone only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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