Beta blocker

Beta blockers
Drug class
Propranolol
Skeletal formula of propranolol, the first clinically successful beta blocker
Class identifiers
Synonymsβ-blockers, beta-adrenergic blocking agents, beta antagonists, beta-adrenergic antagonists, beta-adrenoreceptor antagonists, beta adrenergic receptor antagonists
UseHypertension, arrhythmia, etc.
ATC codeC07
Biological targetbeta receptors
Clinical data
Drug Classes
Best Buy Drugs
RxList
External links
D000319
In Wikidata

Beta blockers, also written β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention).[1] They are also widely used to treat high blood pressure (hypertension), although they are no longer the first choice for initial treatment of most patients.[2]

Beta blockers are competitive antagonists that block the receptor sites for the endogenous catecholamines epinephrine (adrenaline) and norepinephrine (noradrenaline) on adrenergic beta receptors, of the sympathetic nervous system, which mediates the fight-or-flight response.[3][4] Some block activation of all types of β-adrenergic receptors and others are selective for one of the three known types of beta receptors, designated β1, β2 and β3 receptors.[5] β1-adrenergic receptors are located mainly in the heart and in the kidneys.[4] β2-adrenergic receptors are located mainly in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle.[4] β3-adrenergic receptors are located in fat cells.[6]

Beta receptors are found on cells of the heart muscles, smooth muscles, airways, arteries, kidneys, and other tissues that are part of the sympathetic nervous system and lead to stress responses, especially when they are stimulated by epinephrine (adrenaline). Beta blockers interfere with the binding to the receptor of epinephrine and other stress hormones, and weaken the effects of stress hormones.

In 1964, James Black[7] synthesized the first clinically significant beta blockers—propranolol and pronethalol; it revolutionized the medical management of angina pectoris[8] and is considered by many to be one of the most important contributions to clinical medicine and pharmacology of the 20th century.[9]

For the treatment of primary hypertension, meta-analyses of studies which mostly used atenolol have shown that although beta blockers are more effective than placebo in preventing stroke and total cardiovascular events, they are not as effective as diuretics, medications inhibiting the renin–angiotensin system (e.g., ACE inhibitors), or calcium channel blockers.[10][11][12][13]

Medical uses

Large differences exist in the pharmacology of agents within the class, thus not all beta blockers are used for all indications listed below.

Indications for beta blockers include:

Beta blockers have also been used for:

Congestive heart failure

Although beta blockers were once contraindicated in congestive heart failure, as they have the potential to worsen the condition due to their effect of decreasing cardiac contractility, studies in the late 1990s showed their efficacy at reducing morbidity and mortality.[19][20][21] Bisoprolol, carvedilol, and sustained-release metoprolol are specifically indicated as adjuncts to standard ACE inhibitor and diuretic therapy in congestive heart failure, although at doses typically much lower than those indicated for other conditions. Beta blockers are only indicated in cases of compensated, stable congestive heart failure; in cases of acute decompensated heart failure, beta blockers will cause a further decrease in ejection fraction, worsening the patient's current symptoms.

Beta blockers are known primarily for their reductive effect on heart rate, although this is not the only mechanism of action of importance in congestive heart failure.[citation needed] Beta blockers, in addition to their sympatholytic β1 activity in the heart, influence the renin–angiotensin system at the kidneys. Beta blockers cause a decrease in renin secretion, which in turn reduces the heart oxygen demand by lowering extracellular volume and increasing the oxygen-carrying capacity of blood. Heart failure characteristically involves increased catecholamine activity on the heart, which is responsible for a number of deleterious effects, including increased oxygen demand, propagation of inflammatory mediators, and abnormal cardiac tissue remodeling, all of which decrease the efficiency of cardiac contraction and contribute to the low ejection fraction.[22] Beta blockers counter this inappropriately high sympathetic activity, eventually leading to an improved ejection fraction, despite an initial reduction in ejection fraction.

Trials have shown beta blockers reduce the absolute risk of death by 4.5% over a 13-month period. In addition to reducing the risk of mortality, the numbers of hospital visits and hospitalizations were also reduced in the trials.[23]

Anxiety

Officially, beta blockers are not approved for anxiolytic use by the U.S. Food and Drug Administration.[24] However, many controlled trials in the past 25 years indicate beta blockers are effective in anxiety disorders, though the mechanism of action is not known.[25] The physiological symptoms of the fight-or-flight response (pounding heart, cold/clammy hands, increased respiration, sweating, etc.) are significantly reduced, thus enabling anxious individuals to concentrate on the task at hand.

Musicians, public speakers, actors, and professional dancers have been known to use beta blockers to avoid performance anxiety, stage fright, and tremor during both auditions and public performances. The application to stage fright was first recognized in The Lancet in 1976, and by 1987, a survey conducted by the International Conference of Symphony Orchestra Musicians, representing the 51 largest orchestras in the United States, revealed 27% of its musicians had used beta blockers and 70% obtained them from friends, not physicians.[26] Beta blockers are inexpensive, said to be relatively safe, and on one hand, seem to improve musicians' performances on a technical level, while some, such as Barry Green, the author of "The Inner Game of Music" and Don Greene, a former Olympic diving coach who teaches Juilliard students to overcome their stage fright naturally, say the performances may be perceived as "soulless and inauthentic".[26]

Cardiac surgery

The use of beta blockers around the time of cardiac surgery decreases the risk of heart dysrhythmias.[27] Starting them around the time of other types of surgery, however, may worsen outcomes.[27]

Other Languages
العربية: محصر البيتا
bosanski: Beta blokator
čeština: Beta-blokátor
Deutsch: Betablocker
español: Beta bloqueador
français: Bêta-bloquant
한국어: 베타 차단제
hrvatski: Beta blokatori
Bahasa Indonesia: Beta blocker
italiano: Betabloccanti
עברית: חוסמי בטא
Kapampangan: Beta blocker
македонски: Бета блокатор
Bahasa Melayu: Beta blocker
Nederlands: Bètablokker
română: Beta-blocant
Simple English: Beta blocker
српски / srpski: Beta blokator
srpskohrvatski / српскохрватски: Beta blokator
Türkçe: Beta blokör
українська: Бета-блокатор
Tiếng Việt: Thuốc chẹn beta