Write about Vaughan-Williams Classification here.

• Classification system for anti-arrhythmic drugs

Class I:

Local anaesthetic action, reducing Na Current - Sodium Channel Blockade:

• IA Prolong Repolarization

Quinidine

• IB Shortern Repolarization

Lidocaine

• IC Little effect on repolarization

Encainide

Class II:

Beta-blockade

Propanolol

Class III:

Action potential prolongation (Potassium channel blockade + inactivated Na+ channels)

Amiodarone

Class IV:

Calcium channel blockade

Verapimil

Miscellaneous:

Adenosine - Specific to AV node, hyperpolarises cell membrane.  t1/2 = 8-10 seconds

Digitalis

Magnesium