Propafenone Side Effects
Propafenone has numerous side effects affecting multiple body systems, with the most common being gastrointestinal, cardiovascular, and central nervous system effects, occurring in approximately 20% of patients treated with this medication. 1
Common Side Effects
Gastrointestinal Effects
- Unusual taste (14% of patients) 1
- Nausea and/or vomiting (11% of patients) 1
- Constipation (8% of patients) 1
- Diarrhea (2% of patients) 1
- Anorexia (2% of patients) 1
Cardiovascular Effects
- Dizziness (9% of patients) 1
- Wide complex tachycardia (2% of patients) 1
- Congestive heart failure (2% of patients) 1
- Bradycardia (2% of patients) 1
- Palpitations (2% of patients) 1
- First-degree AV block (up to 5% in ventricular arrhythmia patients) 1
- Intraventricular conduction delay (up to 4% in ventricular arrhythmia patients) 1
- Proarrhythmia (1-5% depending on dose) 1
Central Nervous System Effects
- Headache (6% of patients) 1
- Fatigue (6% of patients) 1
- Blurred vision (3% of patients) 1
- Weakness (3% of patients) 1
- Tremor (2% of patients) 1
- Ataxia (2% of patients) 1
Dose-Related Side Effects
The incidence of certain side effects increases with higher doses of propafenone 1:
- Dizziness: 4% at 450 mg/day, increasing to 11% at ≥900 mg/day
- Nausea/vomiting: 2% at 450 mg/day, increasing to 9% at ≥900 mg/day
- Unusual taste: 3% at 450 mg/day, increasing to 6% at ≥900 mg/day
- Constipation: 2% at 450 mg/day, increasing to 5% at ≥900 mg/day
Serious Cardiovascular Side Effects
Propafenone can cause serious cardiovascular side effects that require careful monitoring 2, 3:
- Ventricular tachycardia and ventricular fibrillation 3
- QRS prolongation (an increase >25% from baseline indicates potential proarrhythmic risk) 3
- Rapid atrial flutter with 1:1 AV conduction 2
- Worsening of heart failure 2
Contraindications and Special Precautions
Propafenone should be avoided in certain patient populations 2, 3:
- Patients with heart failure or reduced left ventricular ejection fraction 3
- Patients with structural heart disease 2
- Patients with severe obstructive lung disease 2
- Patients with sinus or AV conduction disease (in absence of pacemaker) 2
- Patients with cardiogenic shock 2
- Patients with hypotension 2
- Patients with Brugada syndrome 2
Less Common but Serious Side Effects
Propafenone can occasionally cause these serious adverse effects 1:
- Hepatic abnormalities including hepatitis and cholestasis (0.1-0.2%) 1
- Hematologic effects including agranulocytosis, anemia, thrombocytopenia 1
- Lupus-like syndrome (positive ANA in 0.7% of patients) 1
- Neurological effects including seizures (0.3%), confusion, memory loss 1
Monitoring Recommendations
To minimize risks associated with propafenone therapy 2, 3:
- Regular ECG monitoring is essential during initiation and dose adjustments 3
- Monitor for QRS prolongation 3
- Use with caution in patients with mild structural heart abnormalities 3
- Be aware of drug interactions, particularly with digoxin, warfarin, metoprolol, and propranolol 4
Discontinuation Rates
About 15% of patients discontinue propafenone due to adverse effects 5. The incidence of side effects is related to dose and age >65 years, with cardiovascular toxicity occurring more frequently in patients with heart disease (20% vs 13% in those without heart disease) 5.