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Beta Blockers

Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

• What are beta blockers and how do they work?
• For what conditions are beta blockers used?
• Are there any differences between beta blockers?
• What are the side effects of beta blockers?
• With which drugs do beta blockers interact?
• What are some examples of beta blockers?

What are beta blockers and how do they work?

Beta blockers, also known as beta-adrenergic blocking agents, are drugs that block norepinephrine and epinephrine (adrenaline) from binding to beta receptors on nerves. There are three types of beta receptors and they control several functions based on their location in the body.

• Beta-1 (β1) receptors are located in the heart, eye, and kidneys;
  
  
• beta (β2) receptors are found in the lungs, gastrointestinal tract, liver, uterus, blood vessels, and skeletal muscle; and
  
  
• beta (β3) receptors are located in fat cells.

Beta blockers primarily block β1 and β2 receptors. By blocking the effect of norepinephrine and epinephrine, beta blockers reduce heart rate; reduce blood pressure by dilating blood vessels; and may constrict air passages by stimulating the muscles that surround the air passages to contract.

For what conditions are beta blockers used?

Beta blockers are used for treating:

• abnormal heart rhythm,
  
  
• high blood pressure,
  
  
• heart failure,
  
  
• angina (chest pain),
  
  
• tremor,
  
  
• pheochromocytoma, and
  
  
• prevention of migraines.

They also have been found to prevent further heart attacks and death after a heart attack. Other uses include the treatment of hyperthyroidism, akathisia (restlessness or inability to sit still), and anxiety. Some beta blockers reduce the production of aqueous humor in the eye and therefore are used for reducing pressure in the eye caused by glaucoma.

Are there any differences between beta blockers?

Beta blockers differ in the type of beta receptors they block and, therefore, their effects.

• Non-selective beta blockers, for example, propranolol (Inderal), block β1 and β2 receptors and, therefore, affect the heart, blood vessels, and air passages.
  
  
• Selective beta blockers, for example, metoprolol (Lopressor, Toprol XL) primarily block β1 receptors and, therefore, mostly affect the heart and do not affect air passages.
  
  
• Some beta blockers, for example, pindolol (Visken) have intrinsic sympathomimetic activity (ISA), which means they mimic the effects of epinephrine and norepinephrine and can cause an increase in blood pressure and heart rate. Beta blockers with ISA have smaller effects on heart rate than agents that do not have ISA.
  
  
• Labetalol (Normodyne, Trandate) and carvedilol (Coreg) block beta and alpha-1 receptors. Blocking alpha receptors adds to the blood vessel dilating effect of labetalol (Normodyne, Trandate) and carvedilol (Coreg).