Beta blocking agents

Beta blockers
Drug class
Skeletal formula of propranolol, the first clinically successful beta blocker
Class identifiers
Synonyms	β-blockers, beta-adrenergic blocking agents, beta antagonists, beta-adrenergic antagonists, beta-adrenoreceptor antagonists, beta adrenergic receptor antagonists
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

Beta blocker, also written β-blocker, is a class of medications that are particularly used to manage cardiac arrhythmias, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention). They are also widely used to treat hypertension, although they are no longer the first choice for initial treatment of most patients.

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. 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.β₁-adrenergic receptors are located mainly in the heart and in the kidneys.β₂-adrenergic receptors are located mainly in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle.β₃-adrenergic receptors are located in fat cells.

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.