Final answer:
Labetalol (D) has the greatest oral bioavailability among the beta blockers listed. Beta blockers reduce blood pressure and heart rate by blocking adrenergic receptors in the heart. Labetalol is particularly effective when taken orally due to its high bioavailability.
Step-by-step explanation:
The beta blocker with the greatest oral bioavailability is Labetalol (D). Beta blockers, also known as β-blockers, are commonly used in the treatment of cardiovascular diseases. They function by binding to G-protein-linked receptors in heart muscles, thus blocking adrenaline. This binding leads to vasoconstriction and cardioacceleration, ultimately reducing blood pressure and heart rate. Labetalol has the highest oral bioavailability among the options listed, meaning that a greater percentage of the drug enters the systemic circulation when given orally.Other β-blockers mentioned, such as metoprolol, target specific receptors like the B1-receptor, while propranolol is a non-specific blocker of β-receptors. Medications like candesartan, eprosartan, and irbesartan are angiotensin II receptor blockers and work through a different mechanism.