Adrenergic β-antagonists (β-blockers)
Adrenergic β-antagonists block both β1 and β2 receptors. β1-receptors on heart muscle cells are blocked; this results in decrease in heart frequency. β-receptors on smooth muscle cells in blood vessels are blocked as well.
I. Propranolol is a non-selective β-blocker.
II. A β-antagonist may cause impotention.
Extra info: Non-selective β-blockers like propranolol block both β1 and β2 receptors. Impotence can be an adverse effect of β-blockers.