Nifekalant hydrochloride is primarily used in the treatment of life-threatening ventricular arrhythmias, particularly in cases where other antiarrhythmic drugs have proven ineffective. It functions as a potassium channel blocker, effectively prolonging the action potential duration and refractory period in cardiac cells, which helps restore normal heart rhythm. This makes it a valuable option in emergency settings for managing conditions like ventricular tachycardia or fibrillation. Its rapid onset of action and intravenous administration allow for quick intervention in critical situations. However, careful monitoring is required due to the risk of proarrhythmic effects and potential QT interval prolongation.