Flecainide is a commonly used IC antiarrhythmic. Clinical presentations of Flecainide toxicity are not commonly described.

A 62 year old man on dialysis presented for evaluation of outpatient bradycardia and hypotension. In the ED, patient had wide-complex rhythm with heart rates ranging from 76 to 127. The previous day, Flecainide and Metoprolol were discontinued and patient was dialyzed and discharged. The patient was treated empirically for possible hyperkalemia. No significant change in ECG was noted with administration of calcium. Sodium bicarbonate produced questionable benefit. Potassium level was 4.6 mmol/L. Cardiac rhythm fluctuated between sinus rhythm and wide complex tachycardia in the ED & ICU. Flecainide level was 2.1 μg/ml (normal <1 μg/ml). Toxicity developed despite previous discontinuation and dialysis prior to presentation because of Flecainide's large volume of distribution and lipopholicity.

Although Flecainide toxicity is uncommon, it has a high mortality rate, requiring early identification and treatment. Flecainide toxicity can develop in patients with hepatic or renal insufficiency, and can manifest with ventricular tachycardia or bradycardia. If suspicion of Flecainide toxicity arises, lidocaine and procainamide should be avoided to prevent further sodium channel blockade. Absence of response to calcium for a very wide complex QRS should raise clinicians' suspicion that WCT is not due to hyperkalemia, emphasizing the importance of reviewing patients' home medications. Sodium bicarbonate should be administered early to treat widened QRS. Amiodarone, intralipid emulsion therapy and ECMO may be considered in severe cases.