Antiarrhythmic drugs

Last updated: March 18, 2022

Summarytoggle arrow icon

Antiarrhythmic drugs are used to prevent recurrent arrhythmias and restore sinus rhythm in patients with cardiac arrhythmias. These drugs are classified based on their electrophysiological effect on the myocardium. Antiarrhythmic drugs do not improve the survival of patients with non-life-threatening arrhythmias and may increase mortality, particularly in patients with structural heart disease. They are associated with severe adverse effects, primarily due to their proarrhythmic effects on the myocardium. Patients who have received an intravenous antiarrhythmic should be monitored closely with serial ECGs. Several classes of antiarrhythmics, including beta blockers, calcium channel blockers, amiodarone, cardiac glycosides, and lidocaine, also have other medical uses, which are discussed in their respective articles.

Overviewtoggle arrow icon

Classes of antiarrhythmic drugs [1][2]
Class Drug group Mechanism of action Examples Use Adverse effects

Class I antiarrhythmics

Class IA antiarrhythmics
  • Reduce or even block conduction (negative dromotropy), particularly in depolarized tissue (e.g., during tachycardia)
  • State-dependent: the faster the heart rate (e.g., tachycardia), the greater the effect
  • Decreases the slope of phase 0 depolarization
  • Stabilize membrane
  • Categorized into 3 subgroups based upon their effects on the Na+ channel and the action potential (AP) duration
  • Moderate blockage of Na+ channels (intermediate association/dissociation)
  • Prolong action potential (AP) duration (right shift)
  • Slow conduction velocity
  • Prolong effective refractory period (ERP) in ventricular APs
  • Weak blockade of the K+ channel
  • Quinidine
  • Procainamide
  • Disopyramide
  • Ajmaline
Class IB antiarrhythmics
  • Weak blockade of Na+ channels (fast association/dissociation)
  • Shorten AP duration
  • Slow conduction velocity
  • No effect on or slight prolongation of ERP
  • Strongest effect on ischemic or depolarized cardiac Purkinje cells and ventricular myocardium
Class IC antiarrhythmics
  • Flecainide
  • Propafenone
Class II antiarrhythmic drugs
Class III antiarrhythmic drugs
  • Inhibit delayed rectifier potassium currents
  • Prolong QT interval
  • Prolong AP duration (reverse use dependence) and ERP
  • No effect on conduction velocity
Class IV antiarrhythmic drugs
  • Inhibit slow calcium channels
  • Decrease slope of phase 0 and 4 slower conduction velocity → increased ERP
  • Prolong AV node repolarization
  • Prolong PR interval
Class V antiarrhythmic drugs
  • Variable mechanisms
  • Inhibits Na+/K+-ATPases → higher intracellular Na+ concentration → reduced efficacy of Na+/Ca2+ exchangers higher intracellular Ca2+ concentration → increased contractility and decreased heart rate

All antiarrhythmic drugs are also potentially proarrhythmic! Intravenous administration should only be performed with continuous cardiac monitoring!

I am Ambivalent about the QUEEn PROofreading my DISsertation”: Class IA antiarrhythmic drugs are QUEEnidine, PROcainamide, DISopyramide.
LInDO MEXIco Is the Best”: LIDOcaine and MEXIletine are class IB antiarrhythmic drugs.

I Can't Fail, Please”: Class IC antiarrhythmics are Flecainide, Propafenone.
I Am Sober, Doctor, for III days”: Ibutilide, Amiodarone, Sotalol, and Dofetilide are class III antiarrhythmic drugs.

Diltiazem and Verapamil Diminish conduction Velocity.

Class IB antiarrhythmic drugs work Best after myocardial infarction; class IC antiarrhythmic drugs are Contraindicated.


Other antiarrhythmic drugstoggle arrow icon

Adenosine (drug) [1]

Avoid adenosine in patients with suspected pre-excitation tachycardia (e.g., WPW), because it may exacerbate the tachycardia via accessory pathway routes.


Magnesium sulfate [1][13]

Ivabradine [14]

IVabradine slows depolarization in phase IV.

Referencestoggle arrow icon

  1. Craig CR, Stitzel RE. Modern Pharmacology with Clinical Applications. Little, Brown Medical Division ; 1997
  2. Blomström-Lundqvist C, Scheinman MM, Aliot EM, et al. ACC/AHA/ESC guidelines for the management of patients with supraventricular arrhythmias--executive summary. Circulation. 2003; 108 (15): p.1871-1909.doi: 10.1161/01.CIR.0000091380.04100.84 . | Open in Read by QxMD
  3. Zehra Pinar K, Necati D, Tansel Ansal B, Ilgin K, Ferat K, Tolga C. Adenosine Stress Myocardial Perfusion Scintigraphy and Echocardiography Application with Same Infusion. International Journal of Clinical Cardiology. 2017; 4 (4).doi: 10.23937/2378-2951/1410106 . | Open in Read by QxMD
  4. McDowell M, Mokszycki R, Greenberg A, Hormese M, Lomotan N, Lyons N. Single‐syringe Administration of Diluted Adenosine. Academic Emergency Medicine. 2019; 27 (1): p.61-63.doi: 10.1111/acem.13879 . | Open in Read by QxMD
  5. Adenosine. Updated: January 1, 2017. Accessed: April 7, 2017.
  6. UpToDate, Lexicomp, Inc. Magnesium sulfate: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: April 7, 2017. Accessed: April 7, 2017.
  7. Koruth JS, Lala A, Pinney S, Reddy VY, Dukkipati SR. The Clinical Use of Ivabradine. J Am Coll Cardiol. 2017; 70 (14): p.1777-1784.doi: 10.1016/j.jacc.2017.08.038 . | Open in Read by QxMD
  8. Razavi M. Safe and effective pharmacologic management of arrhythmias.. Texas Heart Institute journal. 2005; 32 (2): p.209-11.
  9. Oguayo KN, Oyetayo OO, Costa SM, Mixon TA. An Unusual Case of Flecainide-induced QT Prolongation Leading to Cardiac Arrest. Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy. 2014; 34 (5): p.e30-e33.doi: 10.1002/phar.1403 . | Open in Read by QxMD
  10. Manolis AS. Supraventricular Premature Beats. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: March 14, 2016. Accessed: February 19, 2017.
  11. Giardina EG, Zimetbaum PJ. Monitoring and Management of Amiodarone Side Effects. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: February 13, 2017. Accessed: April 5, 2017.
  12. Makielski JC. Myocardial action potential and action of antiarrhythmic drugs. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: September 4, 2013. Accessed: April 7, 2017.
  13. UpToDate. Flecainide: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 1, 2017. Accessed: October 10, 2017.
  14. UpToDate. Quinidine: Drug information. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: January 1, 2017. Accessed: October 10, 2017.
  15. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education ; 2014

Icon of a lock3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer