Uses
Cardiac depressant (anti-arrhythmic).
Definition
ChEBI: An aromatic ketone that is 3-(propylamino)propane-1,2-diol in which the hydrogen of the primary hydroxy group is replaced by a 2-(3-phenylpropanoyl)phenyl group. It is a class 1C antiarrhythmic drug with local anesthetic effects, and is used as the hydroch
oride salt in the management of supraventricular and ventricular arrhythmias.
brand name
Rythmol (Reliant);Arythmol;Nofenan;Nofenon;Nomorytmin;Normotrytmin (r) 10 mg;Prolekofen;Retmonorm;Ryhmonorma;Rythmole;Rytmonorm.
World Health Organization (WHO)
Propafenone, a membrane-stabilizing antiarrhythmic agent, was
introduced into medicine in the mid 1980s. Shortly afterwards, its use became
associated with cases of severe cardiac arrhythmias, which led to notable
restrictions in the drug's indications in at least two countries. See also WHO
comment for flecainide.
General Description
Propafenone, 2-[2＇-hydroxy-3-(propylamino)propoxy]-3-phenylpropiophenone (Rythmol), a classIC antiarrhythmic drug, contains a chiral center and is marketedas the racemic mixture. Therapy with the racemicmixture of propafenone produces effects that can be attributedto both (S) and (R) enantiomers. Although (R) and (S)enantiomers exert similarNa
+channel–blocking effects, the(S) enantiomer also produces aβ-adrenergic blockade. As aresult, the (S) enantiomer is reported to be 40-fold morepotent than the (R) enantiomer as an antiarrhythmic agent.The enantiomers also display stereoselective dispositioncharacteristics. The (R) enantiomer is cleared more quickly.Hepatic metabolism is polymorphic and determined genetically.Ten percent of Caucasians have a reduced capacity tohydroxylate the drug to form 5-hydroxypropafenone. Thispolymorphic metabolism accounts for the interindividualvariability in the relationships between dose and concentrationand, thus, variability in the pharmacodynamic effects ofthe drug. The 5-hydroxy metabolites of both enantiomersare as potent as the parent compound in blocking Na
+channels.Propafenone also depresses the slow inward current ofCa2
+ions.
Mechanism of action
Propafenone has not only pronounced class I
effects but also class II (structure related) and
class IV activities . Accordingly, it has
a broad spectrum of activity against ventricular
and supraventricular arrhythmias.
Clinical Use
Propafenone has been used for acute termination orlong-term suppression of ventricular arrhythmias. It isbound in excess of 95% to 1-acid glycoprotein in theplasma. It is absorbed effectively, but bioavailability is estimatedto be less than 20% because of first-pass metabolism.Less than 1% is eliminated as unchanged drug. Therapywith propafenone may produce effects that can be attributedto both (S) and (R) enantiomers. Thus, the effects may bemodulated because of an enantiomer–enantiomer interactionwhen patients are treated with the racemate.
Side effects
Concurrent administration of propafenone with
digoxin, warfarin, propranolol, or metoprolol increases
the serum concentrations of the latter four drugs.
Cimetidine slightly increases the propafenone serum
concentrations. Additive pharmacological effects can
occur when lidocaine, procainamide, and quinidine are
combined with propafenone.
As with other members of class IC, propafenone
may interact in an unfavorable way with other agents
that depress A-V nodal function, intraventricular conduction,
or myocardial contractility.
Overall, 21 to 32% of patients have adverse effects.
The most common are dizziness or light-headedness,
metallic taste, nausea, and vomiting; the most serious
are proarrhythmic events.
Precautions
Propafenone is contraindicated in the presence of severe
or uncontrolled congestive heart failure; cardiogenic
shock; sinoatrial, A-V, and intraventricular disorders
of conduction; and sinus node dysfunction, such as
sick sinus syndrome. Other contraindications include
severe bradycardia, hypotension, obstructive pulmonary
disease, and hepatic and renal failure. Because of
its weak β-blocking action, propafenone may cause possible
dose-related bronchospasm.This problem is greatest
in patients who are slow metabolizers.
