Beta blockers are prescription medications commonly given to patients with heart disease (especially high blood pressure) or with glaucoma. Beta blockers are able to block the effects of certain chemicals, which cause muscles throughout the body to relax. Depending on the type of beta blocker used, its effects may be short or long lasting.
Nonselective Beta Blockers
As CVPharmacology.com explains, one type of beta blocker is the nonselective type of beta blocker. Beta blockers work to prevent some of the interaction between the nervous system and the heart. They do this by blocking special proteins called beta-receptors, which respond to chemicals produced by the nervous system to control how fast and hard the heart beats. Blocking beta receptors causes the heart to beat more slowly and with less force. Nonselective beta blockers block all beta receptors equally and they were the first kind of beta blocker used for clinical purposes. Examples of these first-generation beta blockers include propanolol, nadolol and timolol.
Selective Beta Blockers
Not all of the beta receptors in the body control the relaxation of blood vessels, however. As a result, the second generation of beta blockers was designed to specifically target those beta receptors (termed beta-1 receptors). This helps reduce the risk of certain side effects, such as bronchoconstriction (closing of the airways) due to blockade of beta-2 receptors, which can be especially dangerous for asthmatics. Examples of these selective beta blockers include metoprolol, acebutolol and bisoprolol.
Combination Alpha-Beta Blockers
Alpha-beta blockers, according to Discovery Health, are compounds that have two kinds of effects. Not only do they block beta receptors, they also are able to block a second type of receptor, called alpha receptors. Alpha receptors cause blood vessels to constrict; blockade of alpha receptors causes the blood vessels to relax, lowering blood pressure. As a result, combination alpha-beta blockers (which include labetalol and carvedilol) work to decrease blood pressure via two distinct mechanisms.
