Quinidine is a pharmaceutical agent that acts as a class I antiarrhythmic agent (Ia) in the heart . It is a stereoisomer of quinine , originally derived from the bark of the cinchona tree.

Like all other class I antiarrhythmic agents, quinidine primarily works by blocking the fast inward sodium current (I Na ). more

Quinidine is a pharmaceutical agent that acts as a class I antiarrhythmic agent (Ia) in the heart . It is a stereoisomer of quinine , originally derived from the bark of the cinchona tree.

Like all other class I antiarrhythmic agents, quinidine primarily works by blocking the fast inward sodium current (I Na ). Quinidine's effect on I Na is known as a use dependent block . This means that at higher heart rates, the block increases, while at lower heart rates the block decreases. The effect of blocking the fast inward sodium current causes the phase 0 depolarization of the cardiac action potential to decrease (decreased V max ). less