ABSTRACT
Antiarrhythmics are classified traditionally according to the Vaughn–Williams system (see Table 25.1). This system is not particularly useful as many drugs are not included (e.g. adenosine and digoxin) and many could fit into more than one category (e.g. amiodarone and sotalol). However, the examiners still expect you to know it. Many of the drugs have actions other than just their antiarrhythmic ones, and they are discussed in more detail in their relevant spider diagrams. Vaughn-Williams classification of antiarrhythmics
Class
Mechanism
Drug
Ia
Blocks fast Na+ channels in cardiac myocytes.
Quinidine, procainamide, disopyramide
↑ Refractory period
Ib
Blocks fast Na+ channels in cardiac myocytes.
Lignocaine, phenytoin, mexiletine
↓ Refractory period
Ic
Blocks fast Na+ channels in cardiac myocytes.
Flecainide, propafenone
No effect on refractory period
II
β-adrenoreceptor blockade
Atenolol, propranolol, esmolol
III
K+ channel blockade
Amiodarone, sotalol, bretylium
IV
Ca2+ channel blockade
Verapamil, diltiazem