Beta-blockers are a class of drugs used to treat hypertension and heart disease. They also may be used to treat hyperthyroidism, anxiety, glaucoma and migraines. Propanolol, metaprolol, labetalol, carvedilol, acebutolol, betaxolol, esmolol, nadolol, nebivolol, sotalol and timolol are examples of beta-blockers. Certain beta-blockers are more selective than others because they only target specific cells in the body.
Function
Beta-blockers block the effects of the chemical messengers, norepinephrine and epinephrine. Norepinephrine and epinephrine mediate the effects of the sympathetic nervous system, more commonly referred to as the "flight-or-fight response." The sympathetic nervous system controls many bodily functions, such as heart rate, gut motility, urinary output and pupil dilation. Epinephrine and norepinephrine are the chemicals which regulate these functions. They do so by stimulating adrenergic receptors on target cells. Beta-blockers bind to the adrenergic receptors for norepinephrine and epinephrine and prevent the actions of epinephrine and norepineprhine. By blocking the effects of these chemical messengers beta-blockers decrease heart rate and reduce blood pressure.
Side Effects
The side effects of beta-blockers include diarrhea, nausea, vomiting, muscle cramps, fatigue, headaches, confusion, depression, dizziness, nightmares and sexual dysfunction.
Drug Interactions
Beta-blockers are often prescribed with other drugs, including ACE inhibitors, diuretics and digoxin to treat heart failure. Many commonly prescribed drugs interact with beta-blockers. These include anti-psychotics, anti-hypertensives and anti-arrhythmics among others.
Precautions
People with second- or third-degree heart block or peripheral arterial disease should not take beta-blockers. Beta-blockers can cause constriction of the airways and are not normally prescribed to asthmatics. Additionally, beta-blockers affect the actions of drugs used to treat type II diabetes.
Warning
Beta-blockers are prescribed by a doctor. Persons taking these drugs should not stop taking these drugs without consulting a doctor because a sudden withdrawal of beta-blockers may cause heart attacks.
