Amiodarone toxicity is related to a unique feature of the antiarrhythmic heart drug class.

Amiodarone—an anti-arrhythmia medication that is sold under the brand names Cordarone, Nexterone and Pacerone—requires several weeks of administration at high loading doses to become effective. This is because, rather than build-up in the circulating blood, the medication is actually stored throughout the body’s tissues, according to Very Well Health.

It isn’t until a maximum overall tissue saturation is achieved—through a loading period generally done under careful monitoring in the hospital—that the medicine can address any issues with abnormal heart rhythm. While this loading is what makes the heart drug work, it is also what can lead to amiodarone toxicity—side effects related to the drug’s presence throughout the anatomy.

A second unique feature of this drug, according to Very Well Health, is how slowly it leaves the body after discontinuance. A common term used for this is a medicine’s “half-life.” The half-life of a drug is usually noted in hours, but with amiodarone, this can be measured over the course of a couple of months or greater.

What Are The Side Effects Associated With Amiodarone Toxicity?

Because it is stored in numerous bodily tissues, amiodarone can affect a number of organ systems. These effects can be missed or not connected to the use of this drug if the patient is not aware of its complicated risk profile or the physician is not carefully monitoring.

As indicated by Healthline, serious side effects posed by amiodarone include, but aren’t limited to, trouble catching your breath, wheezing, coughing, blurry vision, seeing halos around objects, eye sensitivity to light, weakness and fatigue, yellowing of skin or eyes due to liver problems, and thyroid issues often experienced as unexplained weight loss or gain, hair loss, and intolerance to temperature changes.

In a separate Very Well Health article, one of these primary and most lethal side effects—amiodarone lung toxicity—is alleged to take four different potential forms. Acute Respiratory Distress Syndrome (ARDS) is at the top of the list in terms of the level of danger it presents.

ARDS allows the air sacs in the lungs to fill with fluid and this fluid interferes with the gas exchange necessary to oxygenate the body’s tissues. Although only five percent of patients taking this medication develop lung issues related to it, ARDS has a 50 percent survival rate once contracted.

Another toxic lung problem associated with amiodarone is interstitial pneumonitis (IP) in which fluid builds up in those same lung air sacs but slowly over time. Additionally, inflammatory cells also accumulate in the air sacs and stand in the way of oxygenation.

Less frequently encountered but still recognized are the “typical pattern” pneumonias that appear on X-ray as a congestion resembling bacterial pneumonia. This type can be misdiagnosed as such and its cause stemming from use of amiodarone entirely missed.

Finally, sometimes lone lung masses are observed diagnostically. These are often presumed to be tumors or infections which are later ruled out upon the completion of a biopsy and assigned to amiodarone provocation.

Are There Warnings Regarding This Class of Drugs?

According to the American College of Cardiology, the black box warning for amiodarone says the following:

“May cause potentially fatal toxicities, including pulmonary toxicity, hepatic injury, and worsened arrhythmia. Only use for adults with life-threatening arrhythmias when other treatments ineffective or not tolerated.”