Class III antiarrhythmics

The class III antiarrhythmics can be used to treat all arrhythmias, both atrial and ventricular. The fact that they are effective "at all levels" makes this class of antiarrhythmics the most widely used.

How do the class III antiarrhythmics work?

The class III antiarrhythmics act by increasing the length of the cardiac cell action potential and by delaying repolarisation, one of the eight potentials examined by the electrocardiogram (ECG). Their action therefore slows the heart rate. They also prevent recurrences of supraventricular and ventricular arrhythmias. This class is mostly represented by amiodarone and its generics.

Do they have contraindications?

The contraindications for amiodarone are mostly thyroid-related. This is because the tablets contain iodine which may cause hyperthyroidism. They can also cause interstitial pneumonia. The other side effects are less serious. These include photosensitisation – caution is therefore required in the summer - or local cornea deposits in the area beneath the pupil.

Sources:

• Interview with Dr Joël Kerjean, cardiologist in Angers, 20 June 2011
• Principles of Internal Medicine, ed TR Harrison. Flammarion