Amiodarone

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

A healthy heart typically pumps blood at regular intervals of 60 to 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 out and into the rest of the body.

Any disturbance in the rate, rhythm, site of origin, or conduction of the cardiac electrical activity is called an arrhythmia. Arrhythmias can be classified according to their origin. Supraventricular arrhythmias originate above the ventricles, whereas ventricular arrhythmias originate in the ventricles. If left untreated, arrhythmias could lead to sudden and fatal conditions such as cardiac arrest. 

Antiarrhythmic medications work by preventing the generation, or conduction, of this aberrant electrical activity, thereby helping treat arrhythmias. In particular, amiodarone decreases the excitability of the cardiac tissue by prolonging the duration of cardiac tissue activation, thereby preventing the conduction of an unwanted electrical activity from any other source.

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 often deposit in the cornea (transparent outer covering of the eye), making it appear translucent or opaque. Fortunately, this side effect is reversible once the medication is stopped and may not cause any significant vision problems. 

Long-term usage of amiodarone can cause pulmonary toxicity or severe damage to the lungs, resulting in dry cough, shortness of breath, and chest pain. Amiodarone can also affect the heart, leading to sinus bradycardia, as well as arrhythmias such as AV block and QT prolongation. 

Individuals taking amiodarone should not consume alcohol or smoke cannabis while taking amiodarone, as it may cause symptoms such as dizziness and drowsiness. Individuals should also be advised against consuming grapefruit, as this can interfere with the metabolism of amiodarone, allowing it to accumulate in the body, which in turn may increase its side effects.

Amiodarone contains iodine, so those with a known allergy to iodine should avoid it. Otherwise, they could develop mild to severe hypersensitivity reactions that could even be fatal. 

Amiodarone is to be avoided in pregnancy and during the period of conception, as it can affect the fetus, and must also be avoided while breastfeeding, as it is secreted in the breast milk. 

Amiodarone is known to interfere with the action or breakdown of other medications that an individual might already be taking such as other antiarrhythmics, warfarin, digoxin, statins, antihistamines, other antiarrhythmics, antidepressants, and some antibiotics and antimycotics. However, taking these medications is not an absolute contraindication for treatment with amiodarone. Combining amiodarone with any of these medications can be done with caution and under direct supervision of a healthcare provider to minimize side effects and toxicity.