What class of antiarrhythmic agents does the nurse administer to slow the outward movement of potassium during phase 3 of the action potential?
A) Class Ib
B) Class Ic
C) Class II
D) Class III
D
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The class III antiarrhythmics block potassium channels and slow the outward movement of potassium during phase 3 of the action potential, prolonging it. Class Ib drugs depress phase 0 somewhat and actually shorten the duration of the action potential. Class Ic drugs markedly depress phase 0, with a resultant extreme slowing of conduction, but have little effect on the duration of the action potential. The class II antiarrhythmics are beta-adrenergic blockers that block beta-receptors, causing a depression of phase 4 of the action potential.
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