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Alpha-adrenergic agonist

 

 
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Alpha-adrenergic agonist
 
 
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An adrenergic alpha-agonist (or alpha-adrenergic agonist) is a drug that selectively stimulates alpha adrenergic receptor
Adrenergic receptor

The adrenergic receptors are a class of G protein-coupled receptors that are targets of the catecholamines. Adrenergic Receptor s specifically bind and are activated by their endogenous ligands, the catecholamines adrenaline and noradrenaline ....
s. The alpha-adrenergic receptor has two subclasses a1 and a2.

ough complete selectivity between receptor agonism is rarely achieved, some agents have partial selectivity.

a1 agonists
a1 agonists: stimulates phospholipase C activity.






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An adrenergic alpha-agonist (or alpha-adrenergic agonist) is a drug that selectively stimulates alpha adrenergic receptor
Adrenergic receptor

The adrenergic receptors are a class of G protein-coupled receptors that are targets of the catecholamines. Adrenergic Receptor s specifically bind and are activated by their endogenous ligands, the catecholamines adrenaline and noradrenaline ....
s. The alpha-adrenergic receptor has two subclasses a1 and a2.

Classes

Although complete selectivity between receptor agonism is rarely achieved, some agents have partial selectivity.

a1 agonists


a1 agonists: stimulates phospholipase C activity. (vasoconstriction and mydriasis; used as vasopressors, nasal decongestants and eye exams). Selected examples are:
  • Methoxamine
    Methoxamine

    Methoxamine is an a1-adrenergic agonist, similar to phenylephrine. It induces vasoconstriction of skin and splanchnic blood vessels, thereby increasing peripheral vascular resistance and raising mean arterial blood pressure....
  • Methylnorepinephrine
  • Oxymetazoline
    Oxymetazoline

    Oxymetazoline is a selective alpha-1 agonist and partial alpha-2 agonist topical decongestant, used in the form of Oxymetazoline hydrochloride, in products such as Afrin , Dristan, Nasivin, Vicks Sinex, Visine L.R., Sudafed OM, and Zicam....
  • Phenylephrine
    Phenylephrine

    Phenylephrine or Neo-Synephrine is an Alpha-1_adrenergic_receptor agonist used primarily as a decongestant, as an agent to dilate the pupil and to increase blood pressure....
     


a2 agonists

a2 agonists: inhibits adenylyl cyclase activity. (reduce brainstem vasomotor center-mediated SNS activation; used as antihypertensives, sedatives & treatment of opiate and alcohol withdrawal symptoms). Selected examples are:
  • Clonidine
    Clonidine

    Clonidine is a direct-acting alpha-2 adrenergic receptor adrenergic agonist....
     (mixed alpha2-adrenergic and imidazoline-I1 receptor agonist)
  • Guanfacine
    Guanfacine

    Guanfacine is a centrally acting antihypertensive agent. Guanfacine lowers both systolic and diastolic blood pressure by activating the central nervous system a-2 adrenergic receptors, which results in reduced sympathetic outflow leading to reduced Blood vessel tone....
    , (preference for alpha2A-subtype of adrenoceptor)
  • Guanabenz
    Guanabenz

    Guanabenz is an alpha agonist of the alpha-2 type that is used as an antihypertensive drug. It is used to treat high blood pressure .The most common side effects during guanabenz therapy are dizziness, drowsiness, dry mouth, headache and weakness....
     (most selective agonist for alpha2-adrenergic as opposed to imidazoline-I1)
  • Guanoxabenz
    Guanoxabenz

    Guanoxabenz is a metabolite of guanabenz....
     (metabolite of guanabenz)
  • Guanethidine
    Guanethidine

    Guanethidine is an antihypertensive drug that reduces the release of catecholamines, such as noradrenaline. Its mechanism is inhibition of the Na+ATPase dependent pump....
     (periferal alpha2-receptor agonist)
  • Xylazine
    Xylazine

    Xylazine is a medication that is used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle and other large mammals....
    ,
  • Methyldopa
    Methyldopa

    Methyldopa or alpha-methyldopa is a centrally-acting adrenergic antihypertensive medication. Its use is now deprecated following introduction of alternative safer classes of agents....


Undetermined/unsorted

The following agents are also listed as agonists by MeSH
Mesh

Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to spider web or Net in that it has many attached or woven strands....
.
  • amidephrine
    Amidephrine

    Amidephrine is a alpha-adrenergic agonist.References...
  • amitraz
    Amitraz

    Amitraz is an antiparasitic drug. Product names include Aazdieno, Acarac, Aludex, Amitraze, Avartin, Baam, Edrizan, Maitac, Mitac, Mitaban, Triatox, Triatix, Vapcozin Taktic, Triazid, Topline, Tudy, Ectodex, Garial, Danicut, Ovidrex, Acadrex, Bumetran, and Ovasyn....
  • anisodamine
    Anisodamine

    Anisodamine, also known as 7?-hydroxyhyoscyamine, is an alpha-adrenergic agonist.It has been tested as a toxic shock syndrome inhibitor in animals....
  • apraclonidine
    Apraclonidine

    Apraclonidine , also known as Iopidine, is a sympathomimetic used in glaucoma therapy. It is an adrenergic receptor agonist.Apraclonidine is administered at a concentration of 1% for the prevention and treatment of postsurgical eye pressure elevation and 0.5% for short-term adjunctive therapy in patients on maximally tolerated medical...
  • brimonidine
    Brimonidine

    Brimonidine is a medication used to treat glaucoma or ocular hypertension. Alphagan is also used to induce miosis for people suffering from poor night vision after Lasik or PRK surgery....
  • cirazoline
    Cirazoline

    Cirazoline is an adrenergic alpha-agonist....
  • detomidine
    Detomidine

    Detomidine is an imidazole derivative and alpha2-adrenergic agonist, used as a large animal sedative,primarily used in horses. Usually available as detomidine hydrochloride....
  • dexmedetomidine
    Dexmedetomidine

    Dexmedetomidine is a sedative medication used by intensive care units and anesthesiologists, and is marketed under the brand name Precedex in the United States....
  • epinephrine
    Epinephrine

    Epinephrine is a hormone and neurotransmitter.Epinephrine increases the "fight or flight" response of the Sympathetic nervous system of the autonomic nervous system....
  • ergotamine
    Ergotamine

    Ergotamine is an ergopeptine and part of the ergot family of alkaloids; it is structurally and biochemically closely related to ergoline. It possesses structural similarity to several neurotransmitters, and has biological activity as a vasoconstrictor....
  • etilefrine
    Etilefrine

    Etilefrine is a cardiac stimulant used as an antihypotensive....
  • indanidine
    Indanidine

    Indanidine is an alpha-adrenergic agonist.References...
  • lofexidine
    Lofexidine

    Lofexidine is an alpha2-adrenergic receptor agonist, historically used as a short-acting anti-hypertensive, but more commonly used to alleviate physical symptoms of heroin and opiate withdrawal....
  • medetomidine
    Medetomidine

    Medetomidine is a synthetic drug used as both a surgical anesthetic and analgesic. It is a crystalline white alpha-two adrenergic agonist that can be administered as an intravenous drug solution with sterile water....
  • mephentermine
    Mephentermine

    Mephentermine is a cardiac stimulant. It was formerly used in Wyamine nasal decongestant inhalers and before that as a stimulant in psychiatry....
  • metaraminol
    Metaraminol

    Metaraminol is a potent sympathomimetic amine used in the prevention and treatment of hypotension, particularly as a complication of anesthesia....
  • methoxamine
    Methoxamine

    Methoxamine is an a1-adrenergic agonist, similar to phenylephrine. It induces vasoconstriction of skin and splanchnic blood vessels, thereby increasing peripheral vascular resistance and raising mean arterial blood pressure....
  • midodrine
    Midodrine

    Midodrine is an alpha-1-sympathomimetic medication. It is used to treat hepatorenal syndrome and orthostatic hypotension. It is not given before bedtime to avoid supine hypertension; the last dose of midodrine should be taken at least 3 to 4 hours before bedtime....
  • mivazerol
    Mivazerol

    Mivazerol is a alpha-adrenergic agonist.References...
  • naphazoline
    Naphazoline

    Naphazoline is the common name for 2--2-imidazoline hydrochloride. It is a sympathomimetic agent with marked Adrenergic receptor activity. It is a vasoconstrictor with a rapid action in reducing swelling when applied to mucous membrane....
  • norepinephrine
    Norepinephrine

    Norepinephrine or noradrenaline is a catecholamine with dual roles as a hormone and a neurotransmitter.As a stress hormone, norepinephrine affects parts of the brain where attention and responding actions are controlled....
  • norfenefrine
    Norfenefrine

    Norfenefrine is a cardiac stimulant....
  • octopamine
    Octopamine

    Octopamine is a biogenic amine that is closely related to noradrenaline, and has noradrenergic and dopaminergic effects....
  • oxymetazoline
    Oxymetazoline

    Oxymetazoline is a selective alpha-1 agonist and partial alpha-2 agonist topical decongestant, used in the form of Oxymetazoline hydrochloride, in products such as Afrin , Dristan, Nasivin, Vicks Sinex, Visine L.R., Sudafed OM, and Zicam....
  • phenylpropanolamine
    Phenylpropanolamine

    Phenylpropanolamine is a medication ingredient of the phenethylamine family used as a decongestant in prescription and nonprescription cough and cold, and sinus remedies, and some combination allergy medications....
  • rilmenidine
    Rilmenidine

    Rilmenidine is a prescription medication administered to treat hypertension. It is marketed under the brand names HYPERIUM and Tenaxum....
  • romifidine
    Romifidine

    Romifidine is a medication that is used in veterinary medicine as a sedative, anesthetic and analgesic, mainly in large animals such as horses, although it may be used in a wide variety of species....
  • synephrine
    Synephrine

    Synephrine is a drug aimed at encouraging fat loss. While its effectiveness is widely debated, synephrine has gained significant popularity as an alternative to ephedrine, a related substance which has been made illegal or restricted in many countries due to concerns about potential problems with heart disease risk and its use in methampheta...
  • talipexole
    Talipexole

    Talipexole is a dopamine agonist that has been proposed as an antiparkinsonian agent. It also has alpha-adrenergic agonist activity....
  • tizanidine
    Tizanidine

    Tizanidine is a drug which is used as a muscle relaxant. It is a centrally acting a-2 adrenergic agonist. It is used to treat the spasms, cramping, and tightness of muscles caused by medical problems such as multiple sclerosis, spastic diplegia, back pain, or certain other injuries to the vertebral column or central nervous system....


Clinical significance

Alpha-adrenergic agonists are used in the treatment of glaucoma
Glaucoma

Glaucoma is a group of diseases of the optic nerve involving loss of ganglion cell in a characteristic pattern of optic atrophy. Raised intraocular pressure is a significant risk factor for developing glaucoma ....
 by decreasing the production of aqueous fluid by the ciliary bodies of the eye.

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