Antiarrhythmics, antihypertensives, and other cardiac drug classes tested on USMLE Step 1.
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- Name two drugs classified as Class IA antiarrhythmics.
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Quinidine and procainamide.- What toxicity syndrome, marked by tinnitus and headache, is classically caused by quinidine?
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Cinchonism.- What autoimmune-like adverse effect is classically associated with procainamide?
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Drug-induced lupus.- How do Class IB antiarrhythmics affect action potential duration, compared to Class IA?
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They shorten the action potential duration (Class IA prolongs it).- Name a Class IB antiarrhythmic commonly used for ventricular arrhythmias after a myocardial infarction.
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Lidocaine.- How do Class IC antiarrhythmics affect action potential duration?
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They have little to no effect on action potential duration.- Why are Class IC antiarrhythmics generally avoided in patients with structural heart disease?
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They are proarrhythmic and increase mortality risk after a myocardial infarction.- What is the mechanism of Class II antiarrhythmics?
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Beta-adrenergic receptor blockade, which slows SA and AV nodal conduction.- What is the mechanism of Class III antiarrhythmics?
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They block potassium channels, prolonging repolarization and the QT interval.- Why is amiodarone considered pharmacologically unique among Class III antiarrhythmics?
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It also has Class I, II, and IV effects, blocking sodium and calcium channels and beta receptors.- Which two organs require baseline and periodic function testing during long-term amiodarone therapy, due to toxicity risk?
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The thyroid and the lungs.- What is the mechanism of Class IV antiarrhythmics?
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Nondihydropyridine calcium channel blockers that slow conduction through the AV node.- What receptor does adenosine activate to terminate supraventricular tachycardia?
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A1 adenosine receptors on the AV node.- What is the first-line drug for acute termination of paroxysmal supraventricular tachycardia?
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Adenosine.- What is the mechanism by which digoxin increases cardiac contractility?
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It inhibits the Na+/K+ ATPase pump, raising intracellular calcium.
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