Vesnarinone is a novel inotropic agent that displays unique and complex mechanisms of action. It inhibits phosphodiesterase, thereby leading to increased intracellular calcium, and also affects numerous myocardial ion channels, resulting in the prolongation of the opening time of sodium channels and the decrease in the delayed outward and inward rectifying potassium current. In vitro, it has also demonstrates significant effects on cytokine production. MW: 395.46. Purity ≥98% by HPLC