Class III Antiarrhythmics

Class III antiarrhythmics are generally used for the treatment of supraventricular arrhythmias. Amiodarone is the exception because it is also used in the treatment of ventricular tachycardia/fibrillation.  These drugs are united by their mechanism including potassium channel blocker properties. Potassium channel blockers prolong phase III repolarization and increase the refractory period.  Amiodarone also has some Class I, Class II, and Class IV actions.  Amiodarone has many side effects, which are frequently tested. Some of these drugs must be initiated in the hospital because of their propensity to induce arrhythmias.  

Class Drugs

• Amiodarone

• Dronedarone

• Sotalol

• Dofetilide

• Ibutilide

Class Mechanism of Action

Potassium channel blocker

• Prolongs phase III repolarization

• Increases refractory period

See individual drugs

Class III Antiarrhythmics Diagram

Class Applications

See individual drugs

Class Adverse Effects

See individual drugs

Drug Table

Drug Name	Application	Comments	Image
Amiodarone	Management of atrial fibrillation and flutter; Treatment of supraventricular and ventricular tachyarrhythmias	Mechanism of Action; Primary effect from blockade of potassium channels; Also has Class I, II, and IV actions:; Class I - Sodium channel blockade; Class II - Beta-blockade; Class IV - Calcium channel blockade; Adverse Effects (commonly tested); Pulmonary fibrosis; Neuropathy; Hepatotoxicity; Blue-gray skin discoloration; Thyroid toxicity (hyper- or hypo-thyroid); Optic neuritis; Corneal deposits	"Amy Odor"
Dronedarone	Maintenance of sinus rhythm in atrial fibrillation	Mechanism of Action; Derivative of amiodarone with similar mechanism; Adverse Effects; Contraindicated due to increased mortality in: ; -Heart failure; -Permanent atrial fibrillation; Liver failure	"Done Steak" "DARE Shirt""
Sotalol	Maintenance of sinus rhythm in the following conditions:; -Atrial fibrillation; -Atrial flutter; -Paroxysmal supraventricular tachycardia; Treatment of ventricular arrhythmias; Used in patients with LVH and CAD due to beta-blocking properties	Mechanism of Action; Primary effect from blockade of potassium channels; Blocks rapid outward potassium current; Prolongs repolarization and duration of action potentials (increases refractory period); Non-selective Beta-Blocker; Adverse Effects; Commonly initiated in the hospital due to potential to induce arrhythmias; Prolongs QT interval; Adverse effects associated with beta-blockers	"So Tall Lollipop"
Dofetilide	Maintenance of sinus rhythm in persistent atrial fibrillation; Used in patients with heart failure and CAD	Mechanism of Action; Pure potassium channel blocker; Adverse Effects; Commonly initiated in the hospital due to potential to induce arrhythmias	"Doe" "Feta" "Tide"
Ibutilide	Chemical cardioversion of atrial flutter; Rarely used as electrical cardioversion is preferred	Mechanism of Action; Potassium channel blocker; Also has class IA action; Adverse Effects; Commonly initiated in the hospital due to potential to induce arrhythmias	"Ibis" "Tile" "Tide"