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Heart Rhythm Drugs - Class III - Potassium Channel Blockers

Article Index
Heart Rhythm Drugs
Class I - Sodium Channel Blockers
Class II - Beta-Blockers
Class III - Potassium Channel Blockers
Class IV - Calcium Channel Blockers
Class V - Miscellaneous
Medication for Common Rhythm Problems
Page 4 of 7

Are potassium channel blockers beneficial?

Unlike some of the other heart rhythm drugs, class III antiarrhythmics do not increase the risk of dying early in men or women with heart disease.21-23 A version of sotalol increased the risk of dying from heart rhythm disturbances when used to prevent arrhythmias in heart attack patients.24 This risk was higher for women than men.25 That formulation of sotalol is no longer used. The current version of sotalol (Betapace) does not increase the risk of dying from heart rhythm problems when given to people with heart disease.26 Class III antiarrhythmic medications are not used to prevent heart rhythm problems because it is not clear whether they are beneficial in that situation. These medications may be used to treat arrhythmias in men and women with heart disease who are taking beta blockers but continue to experience heart rhythm problems, including atrial fibrillation. Atrial fibrillation is a rapid, disordered contraction of the heart muscles whereby the heart flutters in an uncontrolled manner.

Prescribed Class III Antiarrhythmics

Class III Antiarrhythmics – Potassium Channel Blockers
(check with manufacturer for specific information on each drug)

Generic:

Amiodarone

Dofetilide

Sotalol

Brand:

Cordarone
Pacerone

Tikosyn

Betapace
Betapace AF

Administration:

Oral, intravenous

What is it used for:
  • Treatment of life-threatening recurrent ventricular fibrillation and recurrent ventricular tachycardia that affects blood flow to the heart when these have not responded to available doses of other antiarrhythmic medications
  • Maintenance of normal heart rhythm in patients with atrial fibrillation/flutter for more than 1 week that was corrected to normal heart rhythm; should be reserved for patients with symptoms
  • Correction of atrial fibrillation/flutter to normal heart rhythm

You should not take this medication:
  • When episodes of slow heart rate have caused fainting
  • If you have been diagnosed with:
  • Cardiogenic shock (the heart muscle is so damaged it cannot pump properly, causing a shock-like state)
  • Second- and third-degree heart block (the electrical signals between the upper and lower chambers of the heart are impaired)
  • Abnormally slow heartbeat
  • Uncontrolled congestive heart failure
  • Long QT syndrome—the electrical activation and deactivation of the ventricles takes longer than usual
  • Asthma

Common side effects:

Pregnancy/nursing:
  • Pregnant women should not take amiodarone because it can harm the fetus
  • Women who are nursing should not use these medications; if the treatment is essential, then nursing should be discontinued

 

Choice of Medication

Amiodarone (Pacerone or Cordarone) is better than sotalol for correcting heart rhythm disturbances;27 however, it has a higher risk of very serious side effects. In two major studies, many heart attack patients prescribed amiodarone stopped taking it because of side effects, including serious lung and liver problems.21, 22 In one study of elderly heart attack patients with atrial fibrillation, women treated with amiodarone had a higher risk of developing a slow irregular heartbeat (bradyarrhythmia) requiring permanent pacemaker than men taking amiodarone.28 Because of these risks, sotalol is generally the first choice.29 Dofetilide (Tikosyn) is newer and has not been studied as much as the other class III antiarrhythmics. Both amiodarone and dofetilide have been shown to benefit men and women with heart failure.30, 31 Sotalol and dofetilide may trigger a potentially dangerous rapid heart beat (torsade de pointes), particularly in women.

Amiodarone or sotalol may also be given to people with ICDs to reduce the number of shocks.



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