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What are the characteristics of Class II Vaughn-Williams drugs?
- Beta adrenergic blockers
- Some have Na channel blockade (Propranolol)
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What are the characteristics of Propranolol?
Causes both Na channel and B blockade, slows SA node and ectopic pacemaking, blocks arrhythmias induced by exercise or apprehension
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What drugs are Class II Vaughn-Williams drugs?
Propranolol, Metoprolol, Atenolol, Sotalol, Esmolol
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What are the characteristics of Class III Vaughn-Williams drugs?
K channel blockers, Delayed repolarization and prolonged refractory period
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What are the Class III Vaughn-Williams drugs?
Amiodarone, Ibutilide, Bretylium, Dofetilide
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What are the basic characteristics of Amiodarone?
Prolongs AP by delaying K efflux (also other effects)
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What are the basic characteristics of Ibutilide?
Slows inward movement of Na in addition to delaying K efflux
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What are the basic characteristics of Bretylium?
Supresses Ventricular fibrillation associated w/ MI, first used to treat hypertension
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What are the basic characteristics of Dofetilide?
Prolongs AP by delaying K efflux
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How do Class IV drugs work?
Slow rate of AV conduction in patients with atrial fibrillation, Ca channel blcokers
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What drugs are included in Class IV?
Verapamil and Diltiazem
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What are the basic characteristics of Verapamil?
Blocks Na channels in addition to Ca, Slows SA node in tachycardia
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What are the pharmacological actions of Quinidine?
Inhibits VGSC (open channel blocker), Inhibits delayed rectifier K+ channels (at slower rates greater block of Na+ than K+ channels), Muscarinic receptor antagonist ( AV nodal conduction), Alpha adrenergic receptor antagonist
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What are the actions of Quinidine?
Antimuscarinic (increase in AV nodal transmission of atrial flutter and fibrillation), ↑ threshold for excitability and ↓ automaticity, ↓ conduction velocity (decreases slope of phase 0),↑ duration of QRS (delays conduction),↑ duration of QT interval (delays repolarization), Vasodilation
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What are the adverse actions of Quinidine?
Cinchonism: dizziness, tinnitus, N/V, diarrhea, Hypotension and syncope, Ventricular arrhythmia (2-8% of patients develop torsades de pointes, Women>Men)
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What is Quinidine used for?
Symptomatic ventricular arrhythmias with impaired ventricular function, Recurrent atrial fibrillation after conversion to sinus rhythm
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What has Quinidine use diminished?
Due to high incidence of proarrhythmias
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Does Quinidine compromise ventricular contractility?
No
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Does Lidocaine decreases automaticity?
Yes, especially in ectopic pacemakers
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What type of arrhythmias is Lidocaine not useful in?
Atrial arrhythmias
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Why is Lidocaine not useful for Atrial arrhythmias?
Atrial action potentials are so short that the Na+ channel is in the inactivated state only briefly
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Does Lidocaine block open or inactivated Cardiac Na channels?
Both
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What adverse reactions may Lidocaine cause?
Tremor, dysarthria, ∆ in consciousness most common, also Large IV doses administered rapidly may produce seizures
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What type of Arrhythmias is Lidocaine used to treat?
Acute IV therapy of ventricular arrhythmias
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What drug is Mecilitine a congener of and similar to?
Lidocaine
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Can Mexilitine be given orally?
Yes
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What is Mexilitine used for?
Ventricular arrhythmias
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What are the MOAs of Flecainide?
Blocks Na+ and delayed rectifier K+ currents with similar potencies, Very long recovery from Na+ channel block, Also blocks Ca2+ channels, ↓Decreases sinus node automaticity
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What are the adverse effects of Flecainide?
Dose-related blurred vision = most common
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