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. They are also widely used to treat high blood pressure, although they are no longer the first choice for initial treatment of most people.
Propranolol is a medication of the beta blocker class. It is used to treat high blood pressure, some types of irregular heart rate, thyrotoxicosis, capillary hemangiomas, akathisia, performance anxiety, and essential tremors, as well to prevent migraine headaches, and to prevent further heart problems in those with angina or previous heart attacks. It can be taken orally or by intravenous injection. The formulation that is taken orally comes in short-acting and long-acting versions. Propranolol appears in the blood after 30 minutes and has a maximum effect between 60 and 90 minutes when taken orally.
The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like beta blockers, beta-2 (β2) antagonists and alpha-2 (α2) agonists, which are used to treat high blood pressure and asthma, for example.
Oxprenolol is a non-selective beta blocker with some intrinsic sympathomimetic activity. It is used for the treatment of angina pectoris, abnormal heart rhythms and high blood pressure.
Phenylephrine, sold under the brand names Neosynephrine and Sudafed PE among others, is a medication used as a decongestant for uncomplicated nasal congestion, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, applied to the skin, or as a rectal suppository.
Isoprenaline, also known as isoproterenol and sold under the brand name Isuprel among others, is a sympathomimetic medication which is used in the treatment of acute bradycardia, heart block, and rarely for asthma, among other indications. It is used by injection into a vein, muscle, fat, or the heart, by inhalation, and in the past under the tongue or into the rectum.
Labetalol is a medication used to treat high blood pressure and in long term management of angina. This includes essential hypertension, hypertensive emergencies, and hypertension of pregnancy. In essential hypertension it is generally less preferred than a number of other blood pressure medications. It can be given by mouth or by injection into a vein.
Bisoprolol, sold under the brand name Zebeta among others, is a beta blocker which is selective for the beta-1 receptor and used for cardiovascular diseases, including tachyarrhythmias, high blood pressure, angina, and heart failure. It is taken by mouth.
Fenoldopam mesylate (Corlopam) is a drug and synthetic benzazepine derivative which acts as a selective D1 receptor partial agonist. Fenoldopam is used as an antihypertensive agent. It was approved by the Food and Drug Administration (FDA) in September 1997.
The alpha-2 (α2) adrenergic receptor is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) signal through the α2-adrenergic receptor in the central and peripheral nervous systems.
Nebivolol is a beta blocker used to treat high blood pressure and heart failure. As with other β-blockers, it is generally a less preferred treatment for high blood pressure. It may be used by itself or with other blood pressure medication. It is taken by mouth.
Carteolol is a non-selective beta blocker used to treat glaucoma. It is administered in the form of eye drops.
An adrenergic antagonist is a drug that inhibits the function of adrenergic receptors. There are five adrenergic receptors, which are divided into two groups. The first group of receptors are the beta (β) adrenergic receptors. There are β1, β2, and β3 receptors. The second group contains the alpha (α) adrenoreceptors. There are only α1 and α2 receptors. Adrenergic receptors are located near the heart, kidneys, lungs, and gastrointestinal tract. There are also α-adreno receptors that are located on vascular smooth muscle.
Xamoterol, sold under the brand names Corwin, Carwin, Corwil, and Xamtol among others, is a cardiac stimulant which is used in the treatment of heart failure. It acts as a selective partial agonist of the β1-adrenergic receptor with around 50% intrinsic sympathomimetic activity (ISA). The drug has no significant β2-adrenergic receptor agonistic activity. Xamoterol provides cardiac stimulation at rest but acts as a blocker during exercise. It is taken by mouth.
Beta adrenergic agonists or beta agonists are medications that relax muscles of the airways, causing widening of the airways and resulting in easier breathing. They are a class of sympathomimetic agents, each acting upon the beta adrenoceptors. In general, pure beta-adrenergic agonists have the opposite function of beta blockers: beta-adrenoreceptor agonist ligands mimic the actions of both epinephrine- and norepinephrine- signaling, in the heart and lungs, and in smooth muscle tissue; epinephrine expresses the higher affinity. The activation of β1, β2 and β3 activates the enzyme, adenylate cyclase. This, in turn, leads to the activation of the secondary messenger cyclic adenosine monophosphate (cAMP); cAMP then activates protein kinase A (PKA) which phosphorylates target proteins, ultimately inducing smooth muscle relaxation and contraction of the cardiac tissue.
β1-Adrenergic receptor agonists, also known as beta-1 agonists, are a class of drugs that bind selectively to the β1-adrenergic receptor. As a result, they act more selectively upon the heart. β-Adrenoceptors typically bind to norepinephrine release by sympathetic adrenergic nerves and to circulating epinephrine. The effect of β-adrenoceptors is cardiac stimulation, such as increased heart rate, heart contractility, heart conduction velocity, and heart relaxation.
β adrenergic receptor antagonists were initially developed in the 1960s, for the treatment of angina pectoris but are now also used for hypertension, congestive heart failure and certain arrhythmias. In the 1950s, dichloroisoproterenol (DCI) was discovered to be a β-antagonist that blocked the effects of sympathomimetic amines on bronchodilation, uterine relaxation and heart stimulation. Although DCI had no clinical utility, a change in the compound did provide a clinical candidate, pronethalol, which was introduced in 1962.
Butidrine, sold under the brand names Betabloc, Butidrate, and Recetan among others, is a beta blocker related to pronethalol and propranolol that was developed in the 1960s. It is not cardioselective. It has membrane stabilizing activity but no intrinsic sympathomimetic activity. Similarly to certain other beta blockers, butidrine additionally possesses local anesthetic properties.
Cicloprolol, or cycloprolol, is a β-adrenergic receptor antagonist described as an antihypertensive agent which was never marketed. It has weak partial agonist or intrinsic sympathomimetic activity (30%) at the β-adrenergic receptors. This is higher than that of many other beta blockers but is lower than that of xamoterol (45%). The drug is selective for the β1-adrenergic receptor. It has been studied in the treatment of heart failure.
Peripherally selective drugs have their primary mechanism of action outside of the central nervous system (CNS), usually because they are excluded from the CNS by the blood–brain barrier. By being excluded from the CNS, drugs may act on the rest of the body without producing side-effects related to their effects on the brain or spinal cord. For example, most opioids cause sedation when given at a sufficiently high dose, but peripherally selective opioids can act on the rest of the body without entering the brain and are less likely to cause sedation. These peripherally selective opioids can be used as antidiarrheals, for instance loperamide (Imodium).
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