Question

A nurse is preparing to administer an antiarrhythmic and identifies the drug as a class III potassium channel blocker. Which drug would the nurse be most likely to administer?

A) Amiodarone
B) Flecainide
C) Mexiletine
D) Propafenone

Answer 1

The most likely drug to be administered by the nurse as a class III potassium channel blocker is Amiodarone, as it is widely used for cardiac dysrhythmias. Potassium channel blockers affect the third phase of the action potential, which is the repolarization phase, extending the duration of the action potential and refractory period.

Step-by-step explanation:

Potassium Channel Blockers and Cardiac Action Potential:

Class III antiarrhythmic agents are potassium channel blockers that delay the repolarization of the heart's electrical cycle. The drug the nurse is most likely to administer is A) Amiodarone, which is a commonly used medication in this class. These drugs affect the action potential of cardiac cells by impeding the movement of K+ ions through voltage-gated potassium channels, which extend the duration of the action potential and the refractory period. Specifically, they impact the repolarization phase of the cardiac action potential. This can prevent rapid reactivation of the cells and helps to stabilize the heart rhythm in conditions of cardiac dysrhythmias.

Potassium channel blockers like procainamide and amiodarone are used to treat arrhythmias by affecting the third phase (phase 3) of the cardiac cell action potential, which is the phase of rapid repolarization. By blocking potassium channels, these drugs reduce the efflux of K+ out of the cells, slowing repolarization, and thereby prolonging the refractory period of the heart muscle. This makes it more difficult for arrhythmias to be sustained.