A Case of Near-fatal Flecainide Overdose in a Neonate Successfully Treated with Sodium Bicarbonate

Abstract

Background Flecainide is a class IC antidysrhythmic primarily indicated for ventricular dysrhythmias and supraventricular tachycardia (SVT). Class IC antidysrhythmic overdoses has a reported mortality of 22% and death results from dysrhythmias and cardiovascular collapse. We report a near-fatal flecainide overdose in an 18-day old treated successfully with sodium bicarbonate. Case Report An 18-day old, 2 week premature, 4-kg boy developed persistently high heart rates (220-240 beats/min) and ECG changes consistent with supraventricular tachycardia. There was minimal response to vagal maneuvers, adenosine, and esmolol, and a transthoracic echocardiogram showed no underlying structural abnormality. He was then started on flecainide 4 mg PO Q8h. Following the fourth dose he developed lethargy, cold clammy skin and a heart rate of 40 beats/min with no palpable pulse. Patient was given 0.1 mg of atropine intravenously with an increase to 160 beats/min of the patient's heart rate. The child's cardiac monitor revealed a wide-complex tachycardia with left bundle branch morphology with associated pallor and poor cap refill. Sodium bicarbonate was administered intravenously due to suspected flecainide toxicity. Approximately five minutes after 10 mEq of 8.4% sodium bicarbonate intravenously twice his rhythm converted to a narrow-complex tachycardia. A serum flecainide concentration was 1360 mcg/L (therapeutic, 200-1000 mcg/L) drawn one hour prior to the cardiac arrest. It was later discovered that a 2-fold dosing error occurred: the patient received 8 mg Q8h instead of 4 mg Q8h for four doses. Conclusion Flecainide toxicity in children is rare, especially in neonates. It is important for clinicians to be able to identify and treat this uncommon poisoning.

Ventricular Dysrhythmias Associated with Poisoning and Drug Overdose: A 10-Year Review of Statewide Poison Control Center Data from California

“…Flecainide has been reported to cause widening of the QRS complex responsive to sodium bicarbonate [47,48]. Antiarrhythmic drugs are often used by patients with baseline cardiac disease like cardiomegaly, heart failure and previous known arrhythmia, which may contribute to the risk of …”

Sodium Acetate as a Replacement for Sodium Bicarbonate in Medical Toxicology: a Review

“…Administration of sodium bicarbonate produces a transient increase in sodium ion concentration, while its buffering action raises serum and urine pH. In medical toxicology practice, sodium bicarbonate is most commonly used in the treatment of tricyclic antidepressant (TCA) and salicylate poisoning; it is also effective as an adjuvant therapy for cocaine-induced ventricular dysrhythmias [2] and poisonings with quinine, chloroquine, and other type 1A and 1C antidysrhythmics [3]; methanol and ethylene glycol [4]; 2,4-dichlorophenoxyacetic acid and other chlorphenoxy herbicides [5,6]; and chlorine gas [7]. The rationale for sodium bicarbonate's therapeutic use varies by poisoning agent.…”

Patient-Controlled Analgesia Basal Infusion Overdose; Life-threatening Errors with Flecainide Suspension in Children; Medical Product Error-Prevention Efforts Need to be Shared and Harmonized Internationally

“…3 In a third case, an 18-day-old infant received 4 doses of flecainide 8 mg (0.8 mL of a 10 mg/mL suspension) instead of 4 mg (0.8 mL of a 5 mg/mL), also resulting in wide complex tachycardia and cardiac arrest from which the child recovered. 4 A fourth case involved a 9-month-old infant whose parents were told to increase the dose of flecainide to 4 mL, assuming the concentration was 5 mg/mL as in the original prescription. 1 The parents refilled the prescription at another pharmacy, receiving the drug in a 20 mg/mL concentration.…”