Repeated USMLE Questions- Pharmacology- 277

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Q- Lidocaine is an effective antiarrhythmic because of which of the following mechanisms?

A- It blocks alpha-receptors

B- It block beta-receptors

C- It prolongs QT interval

D- It prolongs PR interval

E- It suppresses excitability in ischemic areas of the heart

E- It suppresses excitability in hypoxic areas of the heart- Lidocaine is sodium channel blocker in fast response fibers. It has no significant effect on QT or BR interval.



Q- Outpatient prophylaxis of superior ventricular tachycardia (SVT) is best accomplished by which of the following medications?

A- Adenosine

B- Diltiazem

C- Lidocaine

D- Procainamide

B- Diltiazem- It is the only drug of the list that acts on the AV node. Others are either used for treatment or have short actions.



Q- Combination of levodopa and carbidopa is recommended. Which of the following explains the significance of this combination?

A- Carbidopa enhances the absorption of levodopa

B- Carbidopa enhances the entry of levodopa into brain

C- Carbidopa enhances the conversion of peripheral levodopa into dopamine

D- Unknown mechanism

B- Carbidopa enhances the entry of levodopa into brain- By Inhibition of peripheral dopa decarboxylase by carbidopa which gives levodopa a chance to enter the brain through blood brain barrier.



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