We report the case of a 46-year-old man who developed syncope, a widened QRS interval, and depressed left ventricular systolic function during propafenone therapy for atrial fibrillation. These acute findings may have been consequent to an increased dosage of propafenone combined with heavy alcohol consumption that led to decreased metabolism of propafenone. In addition, propafenone is known to interfere with liver function, although this patient's test results showed scant evidence of liver abnormalities. Yet another possible factor is the genetic spectrum in the metabolism of propafenone and other class I antiarrhythmic agents. When propafenone is prescribed, we recommend advising patients that alcohol consumption and interactions with other drugs can lead to increased levels of the antiarrhythmic agent, with resultant toxicity that can lead to adverse cardiovascular effects. Patients taking propafenone should also undergo periodic liver function testing. Finally, attention should be paid to voluntary or official recalls of specific antiarrhythmic medications that are of unreliable quality or potency.
Keywords: Anti-arrhythmia agents/administration & dosage/adverse effects; atrial fibrillation/diagnosis/drug therapy/etiology/prevention & control; cytochrome P-450 CYP2D6/genetics; dose-response relationship, drug; heart/drug effects; liver/enzymology/metabolism; propafenone/administration & dosage/adverse effects/therapeutic use.