Quinidine

Abstract

Cinchona bark is an ancient herb with magic medical effects. Quinidine is one of the alkaloids in the cinchona bark, also known as the isomer of antimalarial drug quinine. Quinidine acts as a class I antiarrhythmic agent (Ia) in the heart. The main mechanism of quinidine is to inhibit the fast inward sodium current (INa). It also blocks the slow inward calcium current (ICa), the rapid (IKr) and slow (IKs) components of the delayed potassium rectifier current, and the inward potassium rectifier current (IKI). It directly acts on the cell membrane to prolong the cellular action potential and decrease automaticity. Currently, quinidine has been replaced by new types of drugs because of many adverse effects.