Dofetilide

Dofetilide (Tikosyn®)

Class:
  • Class III Antiarrhythmic agent
Actions:
  • Blocks potassium channels
  • Prolongs action potential duration (prolonged QT interval), but not PR interval or QRS duration
Indications:
  • Symptomatic atrial flutter
  • Symptomatic atrial fibrillation
Pharmacokinetics:
  • Peak: 2 – 3 hours
  • Half-Life: 10 hours
Adverse Effects:
  • Prolonged QT interval, toursades de points (especially with hypkalemia), AV blocks
  • Headache, chest pain, dizziness
  • Nausea, diarrhea, abdominal pain
Signs of Toxicity:
  • prolonged QT interval > 0.44 seconds
  • life-threatening dysrhythmias (toursades do pointes)
Contraindications:
  • QT interval > 0.42 seconds [Risk of toursades de pointes]
  • Ventricular dysrhythmias (PVC's, runs of V-tach)
  • Hypersensitivity to dofetilide
  • Concurrent administration of verapamil, cimetidine, trimethoprim, or ketoconazole
  • Hypokalemia, hypomagnesemia
  • Safety during pregnancy, lactation or with children not established (Category C).
Dosages & Routes: Oral: 

 

  • [Creatinine Clearance > 60 ml/min] 500 mcg PO BID
  • [Creatinine Clearance  40 – 60 ml/min] 250 mcg PO BID
  • [Creatinine Clearance < 40 ml/min] 125 mcg PO BID
Nursing Implications:
  • Drug Interactions:  1) Cimetidine, verapamil, trimethoprim, ketoconazole, prochlorperazine, and megestrol compete with renal excretion of dofetilide causing toxic levels of defetilide; 2) Concurrent use with class I antidysrhythmics, class III antidysrhythmics, phenothiazines, tricyclic antidepressants, and macrolide antibiotics can result in prolonged QT interval and enhance risk of toursades de pointes.
  • Assess renal function, especially creatinine clearance prior to dofetilide therapy.
  • Monitor cardiac rhythm continuously during therapy with dofetilide.
  • Defibrillator and resuscitation cart should be at bedside during first 24 hours of dofetilide therapy.
  • Establish baseline serum electrolyte levels for potassium and magnesium prior to dofetilide therapy.
  • Report to physician and GI alterations like vomiting or diarrhea that might alter serum electrolyte levels.
  • Intervention of choice for stable atrial flutter or atrial fibrillation is elective synchronized cardioversion.

 

References:

Lehne, R.A. (2010). Pharmacology for nursing care (7th ed., p. 547).  St. Louis: Saunders Elsevier.

Wilson, B.A., Shannon, M.T., Shields, K.M., & Stang, C.L. (2007).  Prentice Hall Nurse's Drug Guide 2007 (pp. 544-546).  Upper Saddle River, NJ: Pearson Prentice Hall.

 

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