Pediatric flecainide toxicity from a double dose

A 23-month-old boy was brought to the emergency department of an adult and pediatric tertiary care center 1 hour after an inadvertent “double dose” of 120 mg flecainide (9.2 mg/kg). His electrocardiogram revealed sinus rhythm with a terminal R wave in aVR greater than 7 mm, a bifascicular block, and prolonged QRS and QTc intervals. A dramatic improvement in the bifascicular block and terminal R wave occurred after the administration of sodium bicarbonate. He was discharged after 36 hours with no complications. This case demonstrates that flecainide can cause significant cardiac conduction disturbances in doses much lower than previously described. All supratherapeutic ingestions should be assessed in hospital.