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flecainide (Tambocor)

Tradename: Tambocor. Indications: 1) supraventricular arrhythmias a) atrial fibrillation b) atrial flutter c) paroxysmal supraventricular tachycardia (PSVT) 2) chemical cardioversion of atrial fibrillation 3) prevention & suppression of documented life-threatening ventricular arrhythmias Contraindications: 1) pre-existing 2nd or 3rd degree AV block 2) right bundle branch block associated with left hemiblock 3) cardiogenic shock 4) myocardial depression (impaired ventricular function in the setting of coronary artery disease) 5) ischemic heart disease [5] Caution: 1) pre-existing sinus node dysfunction 2) sick sinus syndrome 3) history of congestive heart failure 4) new bundle-branch block 5) patients with pacemakers 6) renal or hepatic impairment Dosage: 1) start 50-100 mg PO BID - PRN dosing for paraxysmal atrial fibrillation [8] 2) max 400 mg/day Tabs: 50, 100, 150 mg. Dosage adjustment in renal failure: - for creatinine clearance < 20 mL/min, decrease dose by 25-50% Pharmacokinetics: -> metabolized in the liver by cyt P450 2D6 Monitor: 1) baseline serum K+; - correct hypokalemia or hyperkalemia prior to administration [9] 2) plasma flecainide a) hepatic insufficiency b) heart failure (goal is trough < 0.7 ug/mL) c) creatinine clearance < 35 mL/min/1.75 m2 d) concurrent administration of amiodarone (recommended) e) elderly (daily during dose adjustment) [9] Adverse effects: 1) common (> 10%) - dizziness, visual disturbances (blurred vision), dyspnea 2) less common (1-10%) - headache, nausea, fatigue, palpitations, chest pain, asthenia, tremor, constipation, edema, fever, abdominal pain, tachycardia, rash, exacerbation of ventricular arrhythmia (5%) 3) uncommon (< 1%) - bradycardia, heart block, increased PR interval, increased QRS duration, congestive heart failure, nervousness, hypoesthesia, paresthesia, alopecia, blood dyscrasia, hepatic dysfunction 4) other - negative inotropic effect - confusion - irritability Drug interactions: 1) flecainide increases serum levels of digoxin 2) flecainide & propranolol increase each other's serum levels 3) amiodarone, cimetidine, smoking, antacids, carbonic anhydrase inhibitors & verapamil increase flecainide levels 4) flecainide potentiates AV block of beta blockers & Ca+2 channel blockers 5) any pharmaceutical agent that inhibits cyt P450 2D6 may increased levels of flecainide Laboratory: 1) specimen: a) serum, plasma (heparin, EDTA) b) collect at trough concentration 2) methods: GLC, HPLC, FPIA, fluorometry 3) interferences: -> propranol & quinidine interfere with fluorometry 4) flecainide in serum/plasma - therapeutic range: 0.2-1.0 ug/mL (trough) [9] 5) other labs with Loincs - flecainide in gastric fluid - flecainide in urine Mechanism of action: 1) suppresses ventricular ectopy & non sustained ventricular tachycardia (variably effective & not routinely indicated because of proarrhythmic effects) 2) does not favorably affect survival or sudden death 3) increases PR interval > 300 ms 4) increases QRS duration > 180 ms 5) QTc increases

Interactions

drug interactions drug adverse effects of antiarrhythmic agent, Group IC

Related

cytochrome P450 2D6 (cytochrome P450 2D, cytochrome P450 DB1, debrisoquine-4-hydroxylase, CYP2D6)

General

antiarrhythmic agent, Group IC

Properties

MISC-INFO: elimination route LIVER 65% KIDNEY 35% 1/2life 7-23 HOURS therapeutic-range 0.2-1.0 UG/ML toxic-range >1.0 UG/ML protein-binding 32-58% elimination by hemodialysis - pregnancy-category C safety in lactation -

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (ed), Companion Handbook, McGraw Hill, NY, 1994
  3. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 157
  4. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  5. Medical Knowledge Self Assessment Program (MKSAP) 11, 19. American College of Physicians, Philadelphia 1998, 2022
  6. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  7. Prescriber's Letter 13(3): 2006 Cytochrome P450 drug interactions Detail-Document#: 220233 (subscription needed) http://www.prescribersletter.com
  8. Prescriber's Letter 12(1): 2005 "Pill-in-the-Pocket" Approach to Treating Atrial Fibrillation Detail-Document#: 210108 (subscription needed) http://www.prescribersletter.com
  9. Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Detail-Document#: 260704 (subscription needed) http://www.prescribersletter.com