What are the most common side effects of propafenone (anti-arrhythmic medication) oral?

Most Common Side Effects of Oral Propafenone

The most common side effects of oral propafenone are unusual/metallic taste (9-14%), nausea and/or vomiting (11%), dizziness (9-13%), constipation (7-8%), headache (5-6%), and fatigue (6%), with gastrointestinal and neurological symptoms being dose-related and generally well-tolerated. 1

Gastrointestinal Side Effects

• Unusual or metallic taste is the single most frequent side effect, occurring in 14% of supraventricular tachycardia (SVT) patients and 9% of ventricular arrhythmia patients, though it rarely leads to discontinuation (1.3% discontinuation rate) 1
• Nausea and/or vomiting affects 11% of patients and is the most common reason for discontinuation among gastrointestinal symptoms (2.9-3.4% discontinuation rate) 1
• Constipation occurs in 7-8% of patients but rarely causes discontinuation (0.2-0.5%) 1
• Diarrhea affects 2-3% of patients 1

Neurological Side Effects

• Dizziness is reported in 9-13% of patients and represents the second most common cause for discontinuation (2.4% discontinuation rate) 1
• Headache occurs in 5-6% of patients but is not increased compared to placebo 1
• Fatigue affects 6% of patients with a 1.0% discontinuation rate 1
• Blurred vision occurs in 3-4% of patients 1
• Tremor is seen in 1-2% of patients 2, 1

Cardiovascular Side Effects

The American Heart Association guidelines note important cardiac adverse effects that, while less common than gastrointestinal/neurological symptoms, carry greater clinical significance:

• First-degree AV block occurs in 3-5% of patients 1
• Intraventricular conduction delay affects approximately 4% of patients 1
• Proarrhythmia (including ventricular tachycardia) occurs in 5% of patients and is the most serious cardiovascular complication, leading to 4.7% discontinuation 1
• Worsening heart failure occurs in 2-4% of patients, particularly in those with pre-existing left ventricular dysfunction 2, 1
• Bradycardia affects 2% of patients 1

Dose-Related Effects

The most common adverse reactions show clear dose-dependency, particularly dizziness (4% at 450mg/day increasing to 11% at ≥900mg/day), nausea/vomiting (2% to 9%), unusual taste (3% to 6%), constipation (2% to 5%), and blurred vision (1% to 3%) 1. This dose-relationship is clinically important because most patients spend more time at higher doses during maintenance therapy 1.

Other Notable Side Effects

• Dyspnea occurs in 2-5% of patients 2, 1
• Weakness affects 2-3% of patients 1
• Dry mouth (xerostomia) is reported in 2% of patients 2, 1

Critical Clinical Context

Approximately 20% of patients discontinue propafenone due to adverse reactions, with the principal causes being nausea/vomiting (3.4%), proarrhythmia (4.7%), dizziness (2.4%), and dyspnea (1.6%) 1. The American College of Cardiology emphasizes that while non-cardiovascular side effects (neurological, gastrointestinal) are generally well tolerated and often resolve with continued therapy or dosage reduction, cardiovascular side effects require more careful monitoring, particularly in patients with underlying ventricular dysfunction 2, 3.