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?
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What are examples of Class IA antiarrhythmics?
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What is Quinidine used for?
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What are the side effects of Quinidine?
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How is Procainamide activated?
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What are the side effects of Procainamide?
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What types of arrhythmias is Procainamide good for?
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What kinds of arrhythmias is Disopyramide useful for?
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What are the characteristics of all Class IB antiarrhythmics?
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What are examples of Class IB antiarrhythmics?
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What kinds of arrhythmias are Lidocaine and Mexiletine used for?
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What are the side effects of Lidocaine?
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What are the side effects of Mexiletine?
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What are the characteristics of all Class IC antiarrhythmics?
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What are examples of Class IC antiarrhythmics?
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When is the use of Flecainide and Propafenone contraindicated?
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What kinds of arrhythmias are treated with Flecainide and Propafenone?
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Beta blockers have been shown to reduce sudden death and all mortality in persons post MI.
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How do Class II antiarrhythmics work?
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What are B1 specific blockers?
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What are non-specific beta blockers?
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What are non-specific alpha and beta blockers?
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What are the characteristics of all Class III antiarrhythmics?
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What are examples of Class III antiarrhythmics?
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What is Amiodarone?
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What kinds of arrhythmias is Amiodarone useful for?
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What are the side effects of Amiodarone?
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What other antiarrhythmic drug does Amiodarone affect?
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Sotalol has mild beta blocking activities as well as its typical class III K+ blocking effects.
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What are the characteristics of class IV antiarrhythmics?
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What is the use of Class IV agents?
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What are the side effects of Class IV?
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What are examples of Class IV drugs?
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What is Digoxin/Digitalis used for?
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Digoxin cannot be used for PAF and it does not terminate AF.
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What are the side effects of Digitalis?
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Where is Digitalis excreted?
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What drugs affect the levels (increase) of Digitalis?
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What is Adenosine?
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How does Adenosine act?
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What kinds of arrhythmias is Adenosine useful for?
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What are the side effects of Adenosine?
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What substances block the effect of Adenosine?
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Procainamide-induced lupus is almost never associated with rash.
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If a man is on warfarin and he is just suddenly put on Amiodarone, what should you do?
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What are three mechanisms of tachyarrhythmias that antiarrhythmic therapy aims to abolish?
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Where are the effects of Class IA on suppressing ectopic pacemakers most pronounced?
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What is the use of Class IA antiarrhythmics?
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Why has the use of Class IA declined?
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Why is Quinidine only given orally?
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Why is Quinidine often coadministered with beta blockers or L-type Ca channel blockers?
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Where is Quinidine metabolized?
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Digoxin levels increase in patients who are put on Quinidine because of decreased clearance.
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What is the metabolism and excretion of Procainamide?
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What are the side effects of Disopyramide?
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Intravenous Lidocaine can suppress the delayed afterdepolarizations caused by drugs like Digoxin.
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What is the use of Class IB antiarrhythmics?
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What is Lidocaine's route of administration?
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What is the metabolism of Lidocaine?
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What is the difference between Lidocaine and Mexiletine?
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What is the most potent of the Class I Na channel blockers?
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What are the side effects of Flecainide?
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What are the side effects of Propafenone?
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What kind of arrhythmias can be treated with beta blockers?
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Which drugs are increased by Amiodarone?
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How is the action of Bretylium tosylate different from other Class III antiarrhythmics?
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What are Ibutilide and Dofetilide?
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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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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.