Amiodarone

Amiodarone decreases the heart’s ability to respond to abnormal electrical stimuli, which—if left unaddressed—may cause an irregular heartbeat.  

A healthy heart typically beats at a regular rate of 60-100 beats per minute. The normal electrical activity of the heart starts in the sinoatrial (SA) node and then spreads through its four chambers—the right and left atria and the right and left ventricles. As a result, the heart contracts, pumping blood throughout the body. 

Any disturbance in the rate, rhythm, site of origin, or conduction of the heart’s electrical activity is known as an arrhythmia. Arrhythmias can be classified according to their origin: supraventricular arrhythmias originate above the ventricles, whereas ventricular arrhythmias start within the ventricles. If left untreated, arrhythmias can lead to sudden and potentially fatal events such as cardiac arrest.  

Antiarrhythmic medications help treat arrhythmias by preventing the generation or conduction of abnormal electrical activity in the heart. In particular, amiodarone decreases the excitability of cardiac tissue by prolonging the duration of its activation, preventing the conduction of unwanted electrical activity from other sources. 

The most common adverse effects of amiodarone include nausea, vomiting, weight loss, bluish-grey discoloration of the skin, hypothyroidism or hyperthyroidism, liver disease, and photosensitivity. In addition, amiodarone can accumulate in the cornea (the transparent outer layer of the eye), making it appear opaque. Fortunately, this side effect is usually reversible after stopping the medication and does not cause any significant vision problems.  

Long-term use of amiodarone can cause pulmonary toxicity, resulting in dry cough, shortness of breath, and chest pain. Amiodarone can also affect the heart, leading to sinus bradycardia (abnormally slow heart rate) and other arrhythmias, such as atrioventricular (AV) block and QT prolongation (a longer recovery time of the heart’s electrical cycle which increases the risk of ventricular arrhythmias).  

A rare, but more severe, side effect of amiodarone is optic neuropathy, which affects the optic nerve – the nerve supplying the eye  – and can cause blurred vision.  

Additional, infrequent side effects include memory loss, confusion, and peripheral neuropathy, which involves nerves that transmit signals between the brain, spinal cord, and the rest of the body. 

Individuals should avoid consuming alcohol or cannabis while taking amiodarone, as this may cause symptoms such as dizziness and drowsiness. Individuals should also avoid grapefruit, as this can interfere with the metabolism of the drug, causing its accumulation in the body and potentially increasing adverse effects. 

Amiodarone contains iodine, so individuals with a known iodine allergy should avoid it. Exposure could trigger mild to severe hypersensitivity reactions, which may be life-threatening.  

Amiodarone should be avoided during pregnancy and when planning conception, as it can harm the fetus, and it should also be avoided during breastfeeding, as it is secreted in breast milk. 

Amiodarone is known to interfere with the activity or metabolism of other medications such as warfarin, digoxin, statins, antihistamines, other antiarrhythmics, antidepressants, and some antibiotics and antimycotics. However, concomitant use is not an absolute contraindication. These medications can be combined cautiously under close supervision by healthcare professionals to minimize toxicity.