Etripamil (MSP-2017) hydrochloride is a short-acting, L-type calcium channel antagonist that can be used in the study of paroxysmal supraventricular tachycardia (PSVT). Etripamil hydrochloride inhibits calcium influx through slow calcium channels, thereby slowing atrioventricular node conduction and prolonging the atrioventricular node refractory period.