Final answer:
Adrenergic blocking drugs affect the transmitters epinephrine and norepinephrine by antagonizing their adrenergic receptors, with β-blockers like metoprolol and propranolol being common examples.
Step-by-step explanation:
The transmitter(s) affected by adrenergic blocking drugs are epinephrine and norepinephrine. These drugs, known as sympatholytic drugs, primarily work as antagonists to adrenergic receptors. β-blockers are a common type of these drugs used to treat cardiovascular diseases by blocking β-receptors associated with vasoconstriction and cardioacceleration. Medications like metoprolol and propranolol are examples of β-blockers that prevent the binding of epinephrine and norepinephrine to their receptors, leading to a decrease in heart rate and dilation of blood vessels, which can improve cardiac function.