Background: Flecainide is an anti-arrhythmic medication with a narrow therapeutic index and a high mortality rate, when overdosed. Few cases of flecainide toxicity in neonates and children due to medication error have been reported in the literature. A case of an accidental flecainide overdose in a neonate in Oman was presented. Case Presentation: A 19-day-old newborn girl developed persistent supra ventricular tachycardia (SVT) after receiving nebulized albuterol for acute bronchitis. After unsuccessful treatment with adenosine, she was given flecainide 5.6 mg orally every 24 hours for resolution of the SVT. On day four of admission, the child inadvertently received 100 mg of flecainide orally due to a dose calculation error. The child developed wide complex tachyarrhythmia followed by pulseless ventricular tachycardia (VT) requiring cardiopulmonary resuscitation. Sodium bicarbonate IV bolus followed by an infusion was administered. The patient developed two additional episodes of pulseless VT that coincided temporally with two interruptions of the sodium bicarbonate infusion, and required high dose of inotropic support. The patient developed convulsions but her brain ultrasound was normal. Her condition stabilized on day three after the toxicity occurred. Repeated echo showed a normal EF. The patient was discharged on propranolol and levetiracetam and was doing well on outpatient follow up. Conclusion: Flecainide is a potentially lethal medication in overdose due to its sodium channel blocking properties. Sodium bicarbonate remains an essential component of treatment.

Keywords: Flecainide, overdose, sodium bicarbonate, VT.