Flecainide

Aka: Flecainide, Tambocor, Flecainide Overdose, Flecainide Toxicity, Flecainide Poisoning

1. See Also
   1. Unknown Ingestion
   2. Class Ic Antiarrhythmic Drug
2. Mechanism
   1. Class Ic Antiarrhythmic Drug
      1. Blocks cardiac Sodium channels
      2. Slows cardiac conduction and decreases cardiac contractility
3. Indications: Atrial Fibrillation Cardioversion
   1. Time to Cardioversion: 3-8 hours
   2. Conversion Rate: 68-91%
   3. Chronic Efficacy: 40-74%
4. Dose
   1. Load: 300-400 mg orally single bolus dose
   2. Maintenance: 50-150 mg orally twice daily
5. Pharmacokinetics
   1. Oral bioavailability: 90%
   2. Peak: 3 hours after ingestion
   3. Volume of Distribution (Vd): 8 to 9 L/kg (high)
      1. Not dialyzable
   4. Half-Life: 12 to 24 hours
   5. Metabolism: Hepatic
      1. Renal excretion: 30% unchanged
6. Precautions
   1. Narrow therapeutic range
   2. Risk of toxicity (esp. in renal dysfunction)
      1. Acute ingestion >1 gram
      2. Chronic dosing error
7. Adverse Effects: General
   1. Neurologic
      1. Dizziness
      2. Visual Disturbance
      3. Headache
   2. Dyspnea
   3. Nausea or Vomiting
   4. Tremor
   5. Fatigue
   6. Paresthesias
8. Adverse Effects: Toxicity or Overdose
   1. See general adverse effects above
   2. Seizures
   3. Hypotension
   4. Bradycardia
   5. Wide Complex Tachycardia
9. Diagnostics: Toxicity or Overdose
   1. Electrocardiogram (EKG)
      1. QRS Widening
      2. Prolonged PR Interval
      3. Terminal R Wave in aVR (last 40 ms)
10. Labs: Toxicity or Overdose
    1. See Unknown Ingestion
    2. Bedside Glucose
    3. Basic chemistry panel with Electrolytes
    4. Serum Calcium
    5. Serum Magnesium
    6. Toxicology labs (including Acetaminophen level)
11. Management: Toxicity or Overdose
    1. Activated Charcoal in alert patient (no aspiration risk) and within one hour of ingestion
    2. Electrolyte disturbance
       1. Potassium Replacement as needed for Hypokalemia
       2. Magnesium Replacement as needed
    3. Hypotension
       1. Initial
          1. Intravenous Fluids
          2. Norepinephrine for Hypotension refractory to fluids
       2. Refractory Hypotension
          1. Intravenous Lipid Emulsion (Intralipid) 20% 1.5 ml/kg to 100 ml bolus (may be repeated)
          2. Extracorporeal Cardiopulmonary Resuscitation (ECMO)
    4. Wide QRS
       1. Hypertonic Sodium Bicarbonate IV with target pH 7.44 to 7.55
    5. Ventricular Tachycardia
       1. Consider Amiodarone or Lidocaine
12. References
    1. Tomaszewski (2022) Crit Dec Emerg Med 36(3): 28
    2. Vu (2015) HeartRhythm Case Rep 2(3):228-31+PMID:28491675 [PubMed]
       1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5419747/