Beta blockers, also known as beta-adrenergic blocking agents, are medications that reduce your blood pressure. Beta blockers work by blocking the effects of the hormone epinephrine, also known as adrenaline. When you take beta blockers, the heart beats more slowly and with less force, thereby reducing blood pressure. Beta blockers also help blood vessels open up to improve blood flow.
Angiotensin-converting enzyme (ACE) inhibitors help relax blood vessels. ACE inhibitors prevent an enzyme in your body from producing angiotensin II, a substance in your body that affects your cardiovascular system by narrowing your blood vessels and releasing hormones that can raise your blood pressure. This narrowing can cause high blood pressure and force your heart to work harder.
Not sure Beta-Blockers or ACE inhibitors are indicated for public speaking.
Diabetics are usually prescribed an ACE inhibitor to protect the kidneys from high blood pressure.
Mayo Clinic Staff