EHNA hydrochloride is a potent and selective dual inhibitor of cyclic nucleotide phosphodiesterase 2 ( PDE2 ) ( IC 50 =4 μM) and adenosine deaminase (ADA) . EHNA hydrochloride exerts a concentration inhibition of the cGMP-stimulated PDE II (cGs-PDE)( IC 50 :0.8 μM (human), 2 μM (porcine myocardium)), but has smaller inhibitory effect on the unstimulated PDE2 activity. EHNA hydrochloride play roles in mediating diverse pharmacological responses, including antiviral , antitumour and antiarrhythmic effects .