Adult: As conventional tab: Initially, 150 mg tid. Dose may be increased to 300 mg bid at intervals of at least 3 days if necessary. Max: 300 mg tid. Patients weighing <70 kg: Dose reduction may be needed. Dose must be individualised based on the patient's response and tolerability. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).
Adult: As conventional tab: Initially, 150 mg tid. Dose may be increased to 300 mg bid or 225 mg 8 hourly at intervals of at least 3 days if necessary. Max: 300 mg tid. Patients weighing <70 kg: Dose reduction may be needed. Dose must be individualised based on the patient's response and tolerability. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).
Oral Atrial fibrillation
Adult: To prolong the time to recurrence of symptomatic cases in patients without structural heart disease: As extended-release cap: Initially, 225 mg 12 hourly. Dose may be increased to 325 mg 12 hourly at intervals of at least 5 days; may be further increased to 425 mg 12 hourly if necessary. Dose must be individualised based on the patient's response and tolerability.
What are the brands available for Propafenone in Thailand?
Propafenone is metabolised by the CYP2D6 isoenzyme into the active metabolite, 5-hydroxypropafenone. International guidelines and drug labels note that it may be metabolised more slowly in patients with variations in their CYP2D6 gene wherein the active metabolite is produced minimally or none. Although available product information may not reference these genes, current international guidelines recommend that genetic testing may be considered to help identify those at significant risk.
Royal Dutch Pharmacists Association - Pharmacogenetics Working Group (DPWG) Guideline as of November 2018:
Genotype
Implications
Recommendations
CYP2D6 ultrarapid metaboliser
Decreased total plasma concentration of propafenone and the active metabolite 5-hydroxypropafenone; increased risk of decreased or no efficacy.
No possible adequate substantial recommendations for dose adjustment. Monitor plasma concentrations, perform an ECG and monitor reduced efficacy. An alternative antiarrhythmic drug not metabolised by CYP2D6 may be given (e.g. sotalol, disopyramide, quinidine, amiodarone).
CYP2D6 intermediate metaboliser
Increased total plasma concentration of
propafenone and the active metabolite 5-hydroxypropafenone; may increase the risk of side effects.
No possible adequate substantial recommendations for dose adjustment. Adjust dose depending on monitoring, perform an ECG and be aware of the side effects. An alternative antiarrhythmic drug not metabolised by CYP2D6 may be given (e.g. sotalol, disopyramide, quinidine, amiodarone).
CYP2D6 poor metaboliser
Increased total plasma concentration of propafenone and the active metabolite 5-hydroxypropafenone; increased risk of side effects.
Decrease the standard dose to 30%, perform an ECG and monitor plasma concentrations.
Hepatic Impairment
Dose reduction may be needed.
Administration
Propafenone May be taken with or without food. ER cap: Swallow whole & do not break/crush. IR tab: Recommendations on taking w/ or w/o food are product-specific. Consult product literature for specific instructions.
Contraindications
Significant structural heart disease (e.g. MI within the last 3 months, uncontrolled CHF where LVEF is <35%, cardiogenic shock [unless arrhythmia-induced], severe symptomatic bradycardia, severe hypotension); sinus node dysfunction, atrial conduction defects, 2nd degree or greater AV block, bundle branch block or distal block in the absence of an artificial pacemaker; known Brugada syndrome; bronchospastic disorders or severe obstructive pulmonary disease; marked electrolyte imbalance; myasthenia gravis.
Special Precautions
Patient with a functional pacemaker, history of heart failure; obstructive airway disease, asthma. CYP2D6 ultrarapid, intermediate, and poor metabolisers. Hepatic and renal impairment. Elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Unmasking of Brugada syndrome; agranulocytosis; CNS effects (e.g. dizziness, fatigue, blurred vision); slow AV conduction which may lead to 1st degree AV block; positive antinuclear antibody titres; prolonged QT interval, new or worsening of pre-existing arrhythmias; may precipitate or exacerbate heart failure; exacerbation of myasthenia gravis; may alter both pacing and sensing thresholds of implanted pacemakers and defibrillators; reversible impairment of spermatogenesis. Cardiac disorders: Palpitations, chest pain. Gastrointestinal disorders: Abdominal pain, vomiting, nausea, diarrhoea, constipation, dry mouth, dysgeusia. General disorders and administration site conditions: Asthenia, pyrexia. Hepatobiliary disorders: Abnormal hepatic function. Nervous system disorders: Headache. Psychiatric disorders: Anxiety, sleep disorders. Respiratory, thoracic and mediastinal disorders: Dyspnoea. Potentially Fatal: Hepatotoxicity (e.g. fulminant hepatitis); ventricular arrhythmias (e.g. ventricular fibrillation, ventricular tachycardia, asystole, torsades de pointes).
This drug may cause dizziness, fatigue, or blurred vision; if affected, do not drive or operate machinery.
Monitoring Parameters
Correct electrolyte disturbances before treatment initiation and as necessary. Monitor pulse (particularly during treatment initiation), ECG, blood pressure, vital signs, and pacemaker function. Assess for signs and symptoms of new or worsening arrhythmias or heart failure.
Overdosage
Symptoms: Headache, dizziness, metabolic acidosis, blurred vision, nausea, tremor, constipation, dry mouth; PQ prolongation, QRS widening, suppression of sinus node activity, AV block, ventricular tachycardia, ventricular fibrillation, cardiac arrest; hypotension due to reduced contractility which may lead to CV shock. In severe cases, tonic-clonic convulsions, paraesthesia, somnolence, and coma. Management: Symptomatic and supportive treatment. Perform defibrillation and administer dopamine and isoprenaline to control rhythm and blood pressure. Treat convulsions with IV diazepam. Respiratory assistance and external cardiac massage may be employed.
Drug Interactions
Local anaesthetics and other medicinal products which have an inhibitory effect on the heart rate and/or myocardial contractility (e.g. β-blockers, TCAs) may increase the risk of adverse reactions. May increase the risk of CNS side effects of IV lidocaine. Increased plasma levels of propranolol, metoprolol, desipramine, ciclosporin, theophylline, and digoxin. May increase the plasma concentration of oral anticoagulants (e.g. phenprocoumon, warfarin) and drugs metabolised by the CYP2D6 isoenzyme (e.g. venlafaxine). May increase the plasma concentration with CYP2D6, CYP1A2 and CYP3A4 inhibitors (e.g. ketoconazole, cimetidine, erythromycin), SSRIs (e.g. fluoxetine, paroxetine), and ritonavir. May enhance the QT-prolonging effect with amiodarone. CYP3A4 inducers (e.g. phenobarbital, rifampicin) may reduce the antiarrhythmic effects.
Food Interaction
Grapefruit juice may increase the serum concentration of propafenone.
Action
Description: Mechanism of Action: Propafenone is a class Ic antiarrhythmic agent. It blocks the fast inward current of Na ions and slows the rate of increase of action potential in Purkinje fibres and, to a lesser extent, myocardial fibres. Additionally, propafenone increases the diastolic excitability threshold, prolongs the effective refractory period, reduces spontaneous automaticity, and lowers triggered activity. Pharmacokinetics: Absorption: Readily and almost completely absorbed from the gastrointestinal tract. Bioavailability: 3.4% (150 mg conventional tab); 10.6% (300 mg conventional tab); less than the conventional tab (relative bioavailability of the extended-release cap). Time to peak plasma concentration: 3.5 hours (conventional tab); 3.8 hours (extended-release cap). Distribution: Crosses the placenta and enters breastmilk. Volume of distribution: 252 L. Plasma protein binding: 95% to α1-acid glycoprotein. Metabolism: Metabolised in the liver mainly by CYP2D6 into 5-hydroxypropafenone, and to a lesser extent by CYP3A4 and CYP1A2 isoenzymes into N-depropylpropafenone (norpropafenone); undergoes further metabolism to glucuronide and sulfate conjugates. Excretion: Via urine (<1% as unchanged drug; the rest as glucuronide or sulfate conjugates); faeces. Elimination half-life: 2-10 hours (extensive metabolisers); 10-32 hours (poor metabolisers).
Chemical Structure
Propafenone Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 4932, Propafenone. https://pubchem.ncbi.nlm.nih.gov/compound/Propafenone. Accessed Aug. 28, 2025.
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