Propafenone, (R)- is an enantiomer Propafenone with anti-arrhythmic activity, and without beta-adrenoceptor antagonist activity. In humans (R)-Propafenone administration resulted in no significant changes in systolic blood pressure, PR interval, QRS duration, and QT and QTc values. The difference between the effects of (R)- and (S)-propafenone on systolic blood pressure and rate pressure product was significant. (R)- and (S)-propafenone exert different beta-blocking actions but equal effects on the sodium channel-dependent antiarrhythmic class 1 activity. Antiarrhythmic class 1 therapy with reduction of beta-blocking side effects may be attained with optically pure (R)-propafenone hydrochloride instead of the currently used racemic mixture.