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Arrhythmias (Heart Rhythm Disturbances) and Class I Drugs

Read more about Class I Drugs.


Class I drugs for arrhythmia treatment are the most prone to side effects outside the circulatory system.

Class IA: Common names include:

  • Quinidine (Quinora, Quinidex, Quinaglute, Cardioquin)
  • Procainamide (Pronestyl)
  • Disopyramide (Norpace)

Class IB: Common names include:

  • Phenytoin (Dilantin)
  • Tocainide (Tonocard)
  • Mexiletine (Mexitil)

Class IC: Common names include:

  • Flecainide (Tambocor)
  • Propafenone (Rythmol)
  • Moricizine (Ethmozine)

Effect of Class I Drugs on Arrhythmias (Heart Rhythm Disturbances)

Like many other drugs used to treat arrhythmias, class I drugs help by slowing the electrical activity in the heart. Drugs in sub-classes IA, IB and IC all work slightly differently, and all drugs in class I work differently than drugs in classes II, III and IV.

Side Effects and Warnings

Possible side effects of class I drugs include:

  • Seizures
  • Confusion
  • Coma
  • Nausea
  • Dry mouth
  • Vomiting
  • Diarrhea
  • Constipation
  • Mental changes
  • Bone marrow damage
  • Clumsiness
  • Vision and hearing changes
  • Rashes
  • Unwanted heart rhythm changes