Known brand names include Pacerone and Nexterone.
A powerful antiarrhythmic, given by mouth (Pacerone) or IV (Nexterone), for life-threatening ventricular fibrillation and unstable ventricular tachycardia when other drugs fail. It can seriously harm the lungs, liver, thyroid, and eyes, and it stays in the body for months.
Amiodarone mainly blocks potassium channels in heart cells, which makes each heartbeat's electrical cycle last longer. It also blocks sodium and calcium channels and dampens adrenaline's effect on the heart. Together these slow signals through the relay point between the upper and lower chambers and make heart tissue wait longer before it can fire again. It also relaxes blood vessels, which can lighten the heart's workload.
As tablets it works slowly, with effects on the rhythm taking at least 2 to 3 days and usually 1 to 3 weeks to appear. Given by IV, it acts sooner, mostly by slowing the relay point between the chambers. It builds up in fat and in organs such as the liver and lungs and leaves the body very slowly, so its effects can last weeks or months after it is stopped. Along with a slower heart rate and longer intervals on an ECG, it can cause a dangerously slow heartbeat, heart block, or make abnormal rhythms worse.
Amiodarone is a powerful heart rhythm medicine for life-threatening fast rhythms that start in the lower chambers of the heart and keep coming back. These include ventricular fibrillation and ventricular tachycardia, a very fast heart rate, when the fast rate leaves blood pressure and blood flow unstable. The goal is to stop these rhythms and keep them from returning.
It is used in adults when other rhythm drugs have not worked or cannot be tolerated. Treatment is started in a hospital or under a specialist's care, either by IV or with tablets. The label limits it to these life-threatening rhythms because it can seriously harm the lungs and liver and can make rhythm problems worse.
Nausea, constipation, poor appetite, tiredness, shakiness, sun sensitivity, blurry vision or halos, and a blue-gray skin color with long use are what people notice. The label treats lung damage as one of the most serious risks, along with liver injury, an underactive or overactive thyroid, a very slow heartbeat or new rhythm problems, and nerve damage in the eye that can cause blindness. Given by IV, it can drop blood pressure and irritate the vein.
A clinician may order these while someone is taking it.
This is the boxed warning, the warning the FDA label prints first.
Oral Pacerone: pulmonary, hepatic, and cardiac toxicity. Use only for the labeled life-threatening arrhythmias, after other agents. Lung toxicity occurs in up to 17% in some series and is fatal about 10% of the time; get a baseline chest X-ray and pulmonary function tests and repeat the X-ray every 3 to 6 months. Liver injury can be fatal; check transaminases and reduce or stop if they rise above three times normal. It can worsen arrhythmias, so start it where continuous ECG and resuscitation are available. The Nexterone IV label has no boxed warning.
Sources: [1]