Amiodarone

What it is

Amiodarone is a highly effective antiarrhythmic used for serious or treatment-resistant heart-rhythm disturbances — including some life-threatening ventricular arrhythmias and difficult atrial fibrillation — usually when safer options have failed or are unsuitable. It is started and supervised by specialists.

How it works

It acts on several of the heart's electrical channels at once, mainly prolonging the recovery phase of heart cells so abnormal rhythms are less able to sustain themselves. This broad, multi-channel action is what makes it so effective and also explains its wide range of effects elsewhere in the body, where the same drug accumulates in tissues over time.

In practice

In practice amiodarone is kept in reserve precisely because it works when little else does, but its very long half-life (it lingers in the body for weeks to months) and its effects on multiple organs make it a drug of careful supervision rather than casual use. The standard of care is a baseline work-up before starting — thyroid, liver, a chest X-ray and often lung function, plus an ECG — and then scheduled thyroid and liver checks roughly every six months, because it can cause both under- and over-active thyroid (it is iodine-rich) and a rise in liver enzymes. It is a potent enzyme inhibitor, so it raises levels of warfarin and digoxin (both usually need their doses cut), and it adds to the QT-prolonging and rate-slowing effects of other drugs. Patients are counselled about photosensitivity and the rare but serious lung and eye effects, and told that any new breathlessness or cough must be reported promptly. Because the drug persists, side-effects and interactions can continue for weeks after it is stopped.