Beta blocker

Beta blockers
Drug class
Skeletal formula of propranolol, the first clinically successful beta blocker.
Class identifiers
Synonyms	beta-blockers, β-blockers, beta-adrenergic blocking agents, beta antagonists, beta-adrenergic antagonists, beta-adrenoreceptor antagonists, beta adrenergic receptor antagonists, BB
Use	Hypertension, arrhythmia, etc.
ATC code	C07
Biological target	beta receptors
Clinical data
Drugs.com	Drug Classes
Consumer Reports	Best Buy Drugs
WebMD	MedicineNet  RxList
External links
MeSH	D000319
Legal status
In Wikidata

Beta blockers, also spelled β-blockers, are a class of medications that are predominantly used to manage abnormal heart rhythms (arrhythmia), and to protect the heart from a second heart attack after a first heart attack (secondary prevention).^[1] They are also widely used to treat high blood pressure, 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]: 152 [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.^[3]: 153 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.^[5]

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^[6] synthesized the first clinically significant beta blockers—propranolol and pronethalol; it revolutionized the medical management of angina pectoris^[7] and is considered by many to be one of the most important contributions to clinical medicine and pharmacology of the 20th century.^[8]

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.^{[9][10][11][12]}