Makindo Medical Notes"One small step for man, one large step for Makindo" |
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📖 The Vaughan–Williams Classification is a traditional system used to categorise anti-arrhythmic drugs based on their predominant mechanism of action on cardiac ion channels or receptors. ⚡ While imperfect (since many drugs have multiple actions), it remains a helpful framework for learning and clinical reference.
| Class | Action | Examples |
|---|---|---|
| Class Ia | ⬆️ Prolongs action potential duration (moderate Na⁺ channel block, some K⁺ block) | Disopyramide, Procainamide, Quinidine |
| Class Ib | ⬇️ Shortens action potential duration (weak Na⁺ block, fast kinetics) | Lidocaine, Mexiletine, Tocainide |
| Class Ic | Minimal effect on action potential duration, but marked Na⁺ channel block | Flecainide, Propafenone |
| Class II | β-blockade: ⬇️ sympathetic activity, slows AV node conduction | Metoprolol, Atenolol, Bisoprolol, Propranolol |
| Class III | ⬆️ Prolong repolarisation (K⁺ channel block → prolongs QT) | Sotalol, Amiodarone, Dofetilide, Ibutilide |
| Class IV | Ca²⁺ channel blockade: slows AV node conduction | Verapamil, Diltiazem |
✅ Clinical Pearl: Remember “Some Block Potassium Channels” → Sodium channel blockers (Ia, Ib, Ic), Beta-blockers (II), Potassium channel blockers (III), Calcium channel blockers (IV).