Antiarrhythmia drugs
Terms
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- Class I
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Na channel blockers
hyperkalemia increases their cardiac toxicity - Class Ia
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Procainamide, Disopyramide, Quinidine
all types of arrhythmias
slows conduction in atria, P fibers, ventricle - Class Ib
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Lidocaine, tocainide
Selectively inhibits P fibers and ventricle - Flecainide
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Class Ic: prolongs QRS
Approved only for v tach that tends to progress to vfib at unpredictable times
(Ic drugs cause greater mortality than placebo) - Procainamide
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common use: arrhythmia during acute phase MI
**causes reversible Lupus (HIPP) - Quinidine
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ass'd w/ torsade de pointes
can cause thrombocytopenic purpura
decreases clearance of digoxin - Disopyramide
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Class IA
-reduces velocity of phase 0 depol (Na channel blockade)
-increases AP duration
-atrial and vent extrasystoles and tachyarrhythmias - Lidocaine
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attenuates phase 4 depol (Ib)
esp for post-MI arrhythmias, digoxin toxicity (Qbank: acute management of vent arrhythmias during ischemia - surgery or MI)
-IV admin - Class II
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Beta-blockers
dec cAMP -> dec Na/Ca currents
esmolol: short-acting, exclusively for acute arrhythmias
Propanolol: prophylactic in px w/ MI b/c has protective effect - Class III
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K channel blockers
increased refractory per and dec ability to respond to tachycardia (hallmark is prolonged AP) - Sotalol
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K blocker, Class III
may -> torsade de pointes - Ibutilide
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for a.flutter and afib
may -> torsade de pointes - Amiodarone
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Class III (increases duration of AP)
broad spectrum
many toxicities, so not used as much
approved for use for refractory arrhythmias (esp ventricular) - Class IV
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Ca channel blockers (verapamil)
AV node - Adenosine
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given as IV bolus -> slows AV node conduction
v. effective against AV node arrhythmias (Drug of Choice)
v. short duration - Digitalis
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for rapid atrial or AV node arrhythmias (has parasympathomimetic action)
-afib, a.flutter
-never give for WPW - makes arrhythmia worse - K+
- depresses ectopic pacemakers, including those caused by digitalis toxicity
- Mg+
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sim to K+
may be effective in some cases of torsade de pointes - Propanolol
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-Class II
-dec SA automaticity, slows AV conduction, inc AV node refratoriness
-ventricular/supraventricular arrhythmias and for slowing vent rate during afib/aflutter