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Related Concept Videos

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers

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Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
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Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

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Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which...
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Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers

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Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of...
2.9K
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers01:20

Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers

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Class IV antiarrhythmic drugs, such as verapamil and diltiazem, block calcium channels. They primarily affect the heart, slowing the conduction in calcium-dependent tissues like the SA and AV nodes. These drugs manage reentrant supraventricular tachycardia (SVT) and reduce ventricular rate in atrial flutter/fibrillation.
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...
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Antianginal Drugs: Calcium Channel Blockers and Ranolazine01:25

Antianginal Drugs: Calcium Channel Blockers and Ranolazine

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Angina pectoris, a primary symptom of ischemic heart disease, requires careful pharmacological interventions. In this context, calcium channel blockers (CCBs) and ranolazine have emerged as crucial pharmacotherapeutic agents, providing deep insights into the complexities of angina management.
CCBs, a diverse class that includes dihydropyridines (nifedipine) and diphenylalkylamines (verapamil and diltiazem), exert their effect by blocking calcium channels in cardiac and smooth muscle cells. This...
1.9K
Antiepileptic Drugs: Potassium Channel Activators01:20

Antiepileptic Drugs: Potassium Channel Activators

1.0K
Ezocgabine or retigabine, an antiepileptic drug of remarkable efficacy, has revolutionized the management of seizures. It is a potassium channel activator, explicitly targeting the family of Q subtype potassium channels. It enhances the transmembrane potassium currents, regulating neuronal excitability. This action stabilizes the resting membrane potential, a pivotal factor in mitigating the hyperexcitability that characterizes epilepsy.
Ezogabine has gained approval as an adjunctive treatment...
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Related Experiment Video

Updated: May 5, 2026

Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates
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New class III antiarrhythmic drugs

D Katritsis1, A J Camm

  • 1Department of Cardiological Sciences, St George's Hospital Medical School, London, U.K.

European Heart Journal
|November 1, 1993
PubMed
Summary

New antiarrhythmic drugs with pure class III activity show promise for treating arrhythmias by prolonging repolarization. However, potential proarrhythmic effects, like torsade de pointes, necessitate careful clinical evaluation.

Area of Science:

  • Cardiology
  • Pharmacology
  • Electrophysiology

Background:

  • New antiarrhythmic compounds with pure class III activity are under development.
  • Class III agents selectively prolong repolarization without slowing conduction.

Purpose of the Study:

  • To evaluate the antiarrhythmic potential and safety of new class III agents.
  • To assess their efficacy against supraventricular and ventricular arrhythmias.

Main Methods:

  • Investigating the electrophysiological actions of class III agents, primarily potassium current blockade.
  • Analyzing effects on action-potential duration and refractoriness in atrial and ventricular myocardium.
  • Examining reverse use-dependence and inotropic effects in animal and clinical studies.

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Main Results:

  • Class III agents effectively prolong repolarization and refractoriness.
  • They show efficacy against re-entrant arrhythmias with minimal negative inotropic effects.
  • Animal studies suggest potential in postinfarction and sudden death prevention.

Conclusions:

  • New class III antiarrhythmic drugs demonstrate significant potential for treating arrhythmias.
  • Concerns exist regarding proarrhythmic tendencies, particularly torsade de pointes.
  • Further clinical evaluation is crucial to establish their therapeutic benefits and safety profile.