CLASS III POTASSIUM CHANNEL BLOCKERS

What is the mechanism of action of Class III potassium channel blockers?

block potassium channels in cardiac tissue, prolonging repolarization.

What is a major effect of blocking potassium channels in cardiac tissue?

It leads to a longer action potential duration and longer refractory period.

Potassium channel blockers stabilizes?

Atria and ventricles

What is the prototype drug for Class III potassium channel blockers?

Amiodarone

What are the main indications for oral amiodarone?

Prevent recurrent ventricular tachycardia (VT) or ventricular fibrillation (VF) and maintain sinus rhythm after Afib/flutter conversion.

First line drugs for emergency ventricular dysrhythmias?

Amiodarone + lidocaine

What are the key risks associated with amiodarone?

Pulmonary toxicity, hepatotoxicity, thyroid issues, and blurry vision, blue- gray skin

What is the black box warning for amiodarone?

It is reserved for life-threatening dysrhythmias only due to serious risks.

What are the nursing implications for patients on amiodarone?

Monitor ECG, HR, BP, check thyroid and liver function tests, and educate patients on potential side effects.

What are contraindications for amiodarone?

Severe bradycardia and cardiogenic shock, 2nd/3rd degree heart block, pregnancy, allergy to iodine

What additional actions does amiodarone have besides blocking potassium channels?

It has effects on sodium channels, beta receptors, and calcium channels, leading to mixed class effects.

Pts should report while taking amiodarone

SOB , dry cough, visual changes, yellow skin/ eyes, irregular heartbeat

What are other class III potassium channel blockers?

Dofetilide, Sotalol, Dronedarone, Ibutilide

What must be monitored for patients taking dofetilide?

Continuous ECG, creatinine clearance (CrCl) and inpatient monitoring due to risk of torsades de pointes.

WHat is Dronedarone?

↓ hospitalizations in paroxysmal/persistent Afib, Has all 4 class effects: Na⁺, K⁺, Ca²⁺, β-block'; less iodine- related toxicity
NOT FOR PT WITH AFIB

What is the primary use of ibutilide?

To convert recent-onset atrial fibrillation or flutter to normal sinus rhythm (NSR).
similar to Sotalol but no B-block effect
Risk of torsades de pointes
Start only with ECG and resuscitation equipment

What is important to know about the use of sotalol?

It has both beta-blocking (low dose) and potassium channel blocking effects (high dose) , with a risk of torsades de pointes.

What is a significant nursing consideration regarding photosensitivity for patients on amiodarone?

Patients should be informed to avoid sun exposure and wear sunscreen.

Why is a loading dose required for amiodarone?

Due to its long half-life and extensive tissue accumulation.