13.01.3 Class I

Class I agents block Na⁺ channels, the channels involved in the rapid depolarisation in the Purkinje system. Examples of class I Na⁺ channel blocker is lignocaine. Lignocaine is also known as lidocaine, and is also used as a local anaesthetic, where the effect is also due to blocking Na⁺ channels. The Na⁺ channel blockers have no effect on sinus rhythm, as Ca²⁺ channels predominantly control sinus rhythm. Lignocaine is used in serious ventricular arrhythmias, where they decrease the excitability of the conduction system.