Quinidine

Quinidine is a D-isomer of quinine present in the bark of the Cinchona tree and similar plant species. This alkaloid was first described in 1848 and has a long history as an antiarrhythmic medication. Quinidine is considered the first antiarrhythmic drug (class Ia) and is moderately efficacious in the acute conversion of atrial fibrillation to normal sinus rhythm. It prolongs cellular action potential by blocking sodium and potassium currents. A phenomenon known as “quinidine syncope” was first described in the 1950s, characterized by syncopal attacks and ventricular fibrillation in patients treated with this drug. Due to its side effects and increased risk of mortality, the use of quinidine was reduced over the next few decades. However, it continues to be used in the treatment of Brugada syndrome, short QT syndrome and idiopathic ventricular fibrillation.

Quinidine is indicated for the management and prophylactic therapy of atrial fibrillation/flutter, as well as the suppression of recurrent documented ventricular arrhythmias. It is also used in the treatment of Brugada syndrome, short QT syndrome and idiopathic ventricular fibrillation..