Final answer:
Amiodarone is a potassium channel blocker that prolongs the repolarization phase of the cardiac action potential, which helps to prevent cardiac dysrhythmias. β-blockers like metoprolol block β1-receptors in the heart, affecting heart rate and vasoconstriction, and can treat hypertension but may decrease cardiac output.
Step-by-step explanation:
Potassium channel blockers, such as amiodarone and procainamide, are medications used to treat cardiac dysrhythmias or abnormal electrical activity in the heart. These drugs impede the movement of K+ through voltage-gated K+ channels. During an action potential, potassium channels primarily affect the repolarization phase, which is when K+ ions exit the cell to help return the cell to its resting state. Blockers of these channels would therefore prolong the repolarization phase, effectively lengthening the action potential duration and refractory period, which can prevent abnormal and potentially dangerous rhythms from occurring.
On the other hand, drugs like metoprolol are β-blockers, which block β-receptors associated with vasoconstriction and cardioacceleration. Metoprolol specifically blocks β1-receptors, controlling the heart rate and offering a treatment mechanism for hypertension. β-blockers can lead to decreased cardiac output and are known as negative inotropic agents.