Antiarrhythmic Drugs Quiz

Questions and Answers

What are the four different classes of antiarrhythmics as classified by Vaughan Williams?

Class I: Na blockers, Class II: Beta blockers, Class III: Potassium blockers, Class IV: Ca2+ channel blockers (L-type, cardiac specific).

What is a good mnemonic to remember examples of anti-arrhythmic drugs?

Professor Q Dissed/ Lydias Poor Mexican Tacos/ Feeling Profaned/ Proper Betty Butt/ Amicable British Socialite/Virtually Dismembered 'IM

What are the characteristics of all Class IA antiarrhythmics?

Bind to activated Na+ channels, slow phase 0 depolarization, prolong the action potential and prolong repolarization.

What is a common risk factor in Class IA antiarrhythmics?

Risk of torsades de pointes due to delayed repolarization. Signup and view all the answers

What are examples of Class IA antiarrhythmics?

Procainamide, Quinidine, Disopyramide. Signup and view all the answers

What is Quinidine used for?

SVT, VT. Signup and view all the answers

What are the side effects of Quinidine?

Allergy-rash/fever, thrombocytopenia, cinchonism, syncope, sudden death, GI side effects. Signup and view all the answers

How is Procainamide activated?

Acetylated by the liver to N-acetyl procainamide. Signup and view all the answers

What are the side effects of Procainamide?

Lupus, agranulocytosis, prolonged QT, and sudden death. Signup and view all the answers

What types of arrhythmias is Procainamide good for?

All types. Signup and view all the answers

What kinds of arrhythmias is Disopyramide useful for?

All types. Signup and view all the answers

What are the characteristics of all Class IB antiarrhythmics?

Bind to inactivated Na+ channels, work mostly in the ventricles, shorten the QT interval. Signup and view all the answers

What are examples of Class IB antiarrhythmics?

Lidocaine, Phenytoin, Mexiletine, Tocainide. Signup and view all the answers

What kinds of arrhythmias are Lidocaine and Mexiletine used for?

Only ventricular tachycardias. Signup and view all the answers

What are the side effects of Lidocaine?

CNS (confusion, seizures, dizziness). Signup and view all the answers

What are the side effects of Mexiletine?

CNS and GI effects. Signup and view all the answers

What are the characteristics of all Class IC antiarrhythmics?

Bind to activated Na+ channels, do not affect action potential length but slow conduction rate. Signup and view all the answers

What are examples of Class IC antiarrhythmics?

Flecainide, Propafenone. Signup and view all the answers

When is the use of Flecainide and Propafenone contraindicated?

When the person has structural heart disease, CAD, or ventricular dysfunction. Signup and view all the answers

What kinds of arrhythmias are treated with Flecainide and Propafenone?

All types, especially supraventricular arrhythmias in structurally normal hearts. Signup and view all the answers

Beta blockers have been shown to reduce sudden death and all mortality in persons post MI.

True Signup and view all the answers

How do Class II antiarrhythmics work?

They block the effect of the sympathetic nervous system and slow conduction in the AV node. Signup and view all the answers

What are B1 specific blockers?

Metoprolol, Esmolol, Atenolol. Signup and view all the answers

What are non-specific beta blockers?

Propranolol, Nadolol. Signup and view all the answers

What are non-specific alpha and beta blockers?

Labetalol, Carvedilol. Signup and view all the answers

What are the characteristics of all Class III antiarrhythmics?

Potassium blockers, prolong QT interval, risk of torsades and sudden death. Signup and view all the answers

What are examples of Class III antiarrhythmics?

Amiodarone, Bretylium, Sotalol. Signup and view all the answers

What is Amiodarone?

One of the most effective antiarrhythmics; must be used with caution. Signup and view all the answers

What kinds of arrhythmias is Amiodarone useful for?

Atrial fibrillation, recurrent VT; first-line agent for emergency treatment. Signup and view all the answers

What are the side effects of Amiodarone?

Torsades de pointes, heart failure, pulmonary fibrosis, hypothyroidism, among others. Signup and view all the answers

What other antiarrhythmic drug does Amiodarone affect?

Can greatly increase digoxin levels causing bradycardia. Signup and view all the answers

Sotalol has mild beta blocking activities as well as its typical class III K+ blocking effects.

True Signup and view all the answers

What are the characteristics of class IV antiarrhythmics?

Block Ca2+ L-type channels, effective in AV and SA node. Signup and view all the answers

What is the use of Class IV agents?

Can terminate SVT and limit the response of ventricles to AF. Signup and view all the answers

What are the side effects of Class IV?

Negative inotropes, constipation, hypotension. Signup and view all the answers

What are examples of Class IV drugs?

Verapamil, Diltiazem. Signup and view all the answers

What is Digoxin/Digitalis used for?

To slow the ventricular response to atrial fibrillation and in systolic heart failure. Signup and view all the answers

Digoxin cannot be used for PAF and it does not terminate AF.

True Signup and view all the answers

What are the side effects of Digitalis?

Heart block, bidirectional ventricular tachycardia, nausea. Signup and view all the answers

Where is Digitalis excreted?

Kidney. Signup and view all the answers

What drugs affect the levels (increase) of Digitalis?

Amiodarone, Procainamide, Class IV. Signup and view all the answers

What is Adenosine?

An endogenous molecule with antiarrhythmic properties. Signup and view all the answers

How does Adenosine act?

Binds to adenosine A1 receptors, activates outward K+ channels, suppresses spontaneous depolarization. Signup and view all the answers

What kinds of arrhythmias is Adenosine useful for?

SVTs. Signup and view all the answers

What are the side effects of Adenosine?

Flushing, bronchoconstriction, chest pain. Signup and view all the answers

What substances block the effect of Adenosine?

Caffeine and theophylline. Signup and view all the answers

Procainamide-induced lupus is almost never associated with rash.

True Signup and view all the answers

If a man is on warfarin and he is just suddenly put on Amiodarone, what should you do?

Decrease dose of warfarin and monitor the INR. Signup and view all the answers

What are three mechanisms of tachyarrhythmias that antiarrhythmic therapy aims to abolish?

(1) Increased automaticity of pacemaker or nonpacemaker cells, (2) Reentrant circuits, (3) Triggered activity. Signup and view all the answers

Where are the effects of Class IA on suppressing ectopic pacemakers most pronounced?

In Purkinje fibers. Signup and view all the answers

What is the use of Class IA antiarrhythmics?

Supraventricular and ventricular tachycardias, reentrant circuits. Signup and view all the answers

Why has the use of Class IA declined?

Because they are proarrhythmic. Signup and view all the answers

Why is Quinidine only given orally?

Quinidine has an alpha antagonistic effect which can cause hypotension when given IV. Signup and view all the answers

Why is Quinidine often coadministered with beta blockers or L-type Ca channel blockers?

Quinidine increases conduction through the AV node which can slow conduction elsewhere. Signup and view all the answers

Where is Quinidine metabolized?

By the liver. Signup and view all the answers

Digoxin levels increase in patients who are put on Quinidine because of decreased clearance.

True Signup and view all the answers

What is the metabolism and excretion of Procainamide?

Some is excreted unchanged by the kidney; some is acetylated and then excreted. Signup and view all the answers

What are the side effects of Disopyramide?

Anticholinergic activity, especially constipation, urinary retention, dry mouth. Signup and view all the answers

Intravenous Lidocaine can suppress the delayed afterdepolarizations caused by drugs like Digoxin.

True Signup and view all the answers

What is the use of Class IB antiarrhythmics?

Suppression of ventricular arrhythmias, especially those associated with ischemia. Signup and view all the answers

What is Lidocaine's route of administration?

IV only. Signup and view all the answers

What is the metabolism of Lidocaine?

Liver (think l=liver). Signup and view all the answers

What is the difference between Lidocaine and Mexiletine?

Mexiletine is administered orally whereas Lidocaine is administered intravenously. Signup and view all the answers

What is the most potent of the Class I Na channel blockers?

Class IC. Signup and view all the answers

What are the side effects of Flecainide?

Dangerous arrhythmias in persons with underlying structural disease, CNS side effects. Signup and view all the answers

What are the side effects of Propafenone?

Weak beta blocking effect. Signup and view all the answers

What kind of arrhythmias can be treated with beta blockers?

SVTs, VTs, inducing tachyarrhythmias from excess catecholamines. Signup and view all the answers

Which drugs are increased by Amiodarone?

Warfarin and Digoxin. Signup and view all the answers

How is the action of Bretylium tosylate different from other Class III antiarrhythmics?

Acts on postganglionic adrenergic nerve terminals, initially releases norepinephrine then inhibits discharge. Signup and view all the answers

What are Ibutilide and Dofetilide?

Class III antiarrhythmics. Signup and view all the answers

Study Notes

Antiarrhythmic Drugs Overview

Vaughan Williams classification includes four classes of antiarrhythmics: Class I (Na+ channel blockers), Class II (Beta blockers), Class III (K+ channel blockers), and Class IV (Ca2+ channel blockers).

Mnemonics for Antiarrhythmics

Use mnemonic: "Professor Q Dissed/Lydias Poor Mexican Tacos/Feeling Profaned/Proper Betty Butt/Amicable British Socialite/Virtually Dismembered 'IM" to recall examples of antiarrhythmic drugs.

Class IA Antiarrhythmics

Bind to activated Na+ channels, slow phase 0 depolarization, and prolong action potential and repolarization.
Common risk: torsades de pointes due to delayed repolarization.
Examples include Procainamide, Quinidine, and Disopyramide.
Quinidine is used for supraventricular tachycardia (SVT) and ventricular tachycardia (VT).
Side effects of Quinidine: allergy (rash/fever), thrombocytopenia, cinchonism, QT prolongation, GI disturbances.
Procainamide is activated in the liver to N-acetyl procainamide and is effective for all types of arrhythmias; side effects include lupus, agranulocytosis, and QT prolongation.
Disopyramide is effective for all arrhythmias but has anticholinergic side effects like constipation and urinary retention.

Class IB Antiarrhythmics

Bind to inactivated Na+ channels, primarily used in the ventricles; they shorten QT interval.
Examples include Lidocaine, Phenytoin, Mexiletine, and Tocainide.
Lidocaine and Mexiletine are effective only for ventricular tachycardias.
Side effects of Lidocaine include CNS effects like confusion and seizures.
Mexiletine, an oral form of Lidocaine, has similar side effects with added GI distress.

Class IC Antiarrhythmics

Bind to activated Na+ channels without affecting action potential length, significantly slowing conduction rate.
Examples include Flecainide and Propafenone, both contraindicated in patients with structural heart disease.
They are effective for supraventricular arrhythmias in structurally normal hearts but can cause dangerous arrhythmias in patients with underlying issues.

Class II Antiarrhythmics (Beta Blockers)

Reduce mortality post-myocardial infarction; block sympathetic nervous system effects.
Examples include Metoprolol, Esmolol (B1 specific), Propanolol, and Nadolol (non-specific), as well as Labetolol and Carvedilol (non-specific alpha and beta blockers).

Class III Antiarrhythmics

K+ channel blockers, prolong QT interval and repolarization, risk of torsades de pointes.
Examples include Amiodarone, Bretylium, and Sotalol.
Amiodarone has a broad spectrum of activity and is first-line for ventricular arrhythmias; side effects include pulmonary fibrosis and hypotension.

Class IV Antiarrhythmics

Block Ca2+ L-type channels, effective primarily at AV and SA nodes.
Used to terminate SVT and manage responses to atrial fibrillation (AF).
Examples are Verapamil and Diltiazem, which can cause hypotension and negative inotropic effects.

Digoxin

Inhibits Na/K ATPase, increases intracellular Ca2+, weakly inotrope for systolic heart failure.
Controls ventricular response in AF; does not terminate AF.
Side effects include heart block, nausea, and visual disturbances.
Excreted by kidneys; increased levels possible with drugs like Amiodarone.

Adenosine

Most effective for rapid termination of reentrant paroxysmal SVTs; acts by hyperpolarizing SA and AV nodes.
Side effects include flushing and bronchoconstriction; contraindicated in asthmatics.

Key Pharmacological Interactions

Amiodarone increases levels of warfarin and digoxin, necessitating dose adjustments.
Drugs like caffeine and theophylline can counteract the effects of adenosine.

Other Antiarrhythmics and Mechanisms

Bretylium affects adrenergic nerve terminals, initially releasing norepinephrine then inhibiting further discharge.
Ibutilide and Dofetilide are identified as Class III antiarrhythmics.

Summary of Effects and Uses

Class IA and IB agents are primarily used in ventricular arrhythmias and may have proarrhythmic potential; Class IC is very potent but risky in patients with heart disease.
Class II and IV agents are essential in management of arrhythmias associated with sympathetic stimulation.
The primary goal of antiarrhythmic therapy is to abolish mechanisms such as increased automaticity, reentrant circuits, and triggered activity.

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Description

Test your knowledge on the various classes of antiarrhythmic drugs as classified by Vaughan Williams. This quiz will cover key definitions, important mnemonics, and the mechanisms of action of these medications. Enhance your understanding and retention of these essential pharmacological concepts.