Vesnarinone (Arkin) (INN) is a mixed phosphodiesterase 3 inhibitor and ion-channel modifier that has modest, dose-dependent, positive inotropic activity, but minimal negative chronotropic activity. It also suppresses cell proliferation and induces apoptosis by inducing the expression of p21, an inhibitor of cyclin-dependent kinase activity in p53-mediated cell cycle arrest.

Vesnarinone HCl (OPC-8212 HCl) is an orally active phosphodiesterase 3 (PDE3) inhibitor.Vesnarinone HCl modulates calcium and potassium ions, increasing calcium flux and decreasing potassium flux.Vesnarinone HCl is a new positive inotropic compound that enhances myocardial contractility and can be be used in heart failure studies.

OPC 18692 is a metabolite of Vesnarinone, a positive inotropic drug developed for congestive heart failure.