Quinidine is an alkaloid, obtained from the bark of cinchona tree, dextrorotatory diastereoisomer of quinine . quinidine (bisulphate and sulphate) is the prototype of class ia antiarrythmic drug, used for the management of atrial flutter and fibrillation.quinidine (sulphate) is a clasantimuscarinic and alpha-blocking properties. it may be effective in suppressing supraventricular and ventricular arrhythmias. it may itself precipitate rhythm disorders, and is best use on spercialist advise.