Antiarrhythmics: Vaughan Williams classification
The Vaughan Williams classification of antiarrhythmics is still widely used although it should be noted that a number of common drugs are not included in the classification e.g. adenosine, atropine, digoxin and magnesium
AP = action potential
AP = action potential
| Class | Examples | Mechanism of action | Notes |
|---|---|---|---|
| Ia | Quinidine Procainamide Disopyramide | Block sodium channels Increases AP duration | Quinidine toxicity causes cinchonism (headache, tinnitus, thrombocytopaenia) Procainamide may cause drug-induced lupus |
| Ib | Lidocaine Mexiletine Tocainide | Block sodium channels Decreases AP duration | |
| Ic | Flecainide Encainide Propafenone | Block sodium channels No effect on AP duration | |
| II | Propranolol Atenolol Bisoprolol Metoprolol | Beta-adrenoceptor antagonists | |
| III | Amiodarone Sotalol Ibutilide Bretylium | Block potassium channels | |
| IV | Verapamil Diltiazem | Calcium channel blockers |