Modes of action Vaughan Williams classification

Class

Action

Examples

I

Reduces rate of rise of action potential:

• Ia: increases action potential duration

disopyramide

• Ib: shortens duration

• Ib: lidocaine

• Ic: little effect

• Ic: flecainide

II

Reduces rate of pacemaker discharge

ß-blockers

III

Prolongs duration of action potential and hence length of refractory period

Amiodarone Sotalol

IV

Antagonises transport of calcium across cell membrane

Verapamil Diltiazem

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