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 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:

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 intrinsicsympathomimetic 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 andalpha-1 receptors. Blocking alpha receptors adds to the blood vessel dilating effect of labetalol (Normodyne, Trandate) and carvedilol (Coreg).

Beta Blockers (cont.)

What are the side effects of beta blockers?

  • Beta blockers may cause:

  • Rash, blurred vision, muscle cramps, and fatigue may also occur. 

  • As an extension of their beneficial effect, they slow heart rate, reduce blood pressure, and may cause heart failure or heart block in patients with heart problems. 

  • Beta blockers should not be withdrawn suddenly because sudden withdrawal may worsen angina (chest pain) and cause heart attacks or sudden death. 

  • Central nervous system effects of beta blockers include:

  • Beta blockers that block β2 receptors may cause shortness of breath inasthmatics. 

  • As with other drugs used for treating high blood pressure, sexual dysfunction may occur. 

  • Beta blockers may cause low or high blood glucose and mask the symptoms of low blood glucose (hypoglycemia) in diabetic patients.

With which drugs do beta blockers interact?

  • Combining propranolol (Inderal) or pindolol (Visken) with thioridazine(Mellaril) or chlorpromazine (Thorazine) may result in low blood pressure (hypotension) and abnormal heart rhythms because the drugs interfere with each others' elimination and result in increased levels of the drugs. 

  • Dangerous elevations in blood pressure may occur when clonidine(Catapres) is combined with a beta blocker, or when clonidine (Catapres) or beta blocker is discontinued after their concurrent use. Blood pressure should be closely monitored after initiation or discontinuation of clonidine (Catapres) or a beta blocker when they have been used together. 

  • Phenobarbital and similar agents may increase the breakdown and reduce blood levels of propanolol (Inderal) or metoprolol (Lopressor, Toprol XL). This may reduce effectiveness of the beta blocker. 

  • Aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs) (for example, ibuprofen) may counteract the blood pressure reducing effects of beta blockers because they reduce the effect of prostaglandins. Prostaglandins play a role in control of blood pressure.

What are some examples of beta blockers?

Reference: FDA Prescribing Information


Last Editorial Review: 1/9/2009

 

 
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