Propafenone, (S)- is an enantiomer Propafenone with anti-arrhythmic and beta-adrenoceptor antagonist activities. In humans (S)-Propafenone administration resulted in a significant reduction of systolic blood pressure and the rate pressure product without any significant effects on heart rate, diastolic 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. The results from the radioligand binding studies indicate that (S)-propafenone exerts beta-blocking activity in the administered dose. This is further supported by a biochemical assay showing (S)-propafenone to be 54 times more potent than the (R)-enantiomer in displacing (S)-(1251)iodocyanopindolol from 3-receptors of sarcolemma-enriched membranes from the guinea pig heart. (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.

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.

Propafenone (brand name Rythmol SR or Rytmonorm) is a class 1C anti-arrhythmic medication, which treats illnesses associated with rapid heartbeats such as atrial and ventricular arrhythmias. The electrophysiological effect of propafenone manifests itself in a reduction of upstroke velocity (Phase 0) of the monophasic action potential. In Purkinje fibers, and to a lesser extent myocardial fibers, propafenone reduces the fast inward current carried by sodium ions, which is responsible for the drugs antiarrhythmic actions. Diastolic excitability threshold is increased and effective refractory period prolonged. Propafenone reduces spontaneous automaticity and depresses triggered activity. At very high concentrations in vitro, propafenone can inhibit the slow inward current carried by calcium but this calcium antagonist effect probably does not contribute to antiarrhythmic efficacy. Propafenone is metabolized primarily in the liver. Because of its short half-life, it requires dosing two or three times daily to maintain steady blood levels. The long-term safety of propafenone is unknown. Because it is structurally similar to another anti-arrhythmic medicine, flecainide, similar cautions should be exercised in its use. Flecainide and propafenone, like other antiarrhythmic drugs, have been shown to increase the occurrence of arrhythmias (5.3% for propafenone, Teva physician prescribing information), primarily in patients with underlying heart disease. However, their use in structurally normal hearts is considered safe.