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