Alpha-adrenergic agonist

Alpha Adrenergic agonist
	Drug class
	; ; Skeletal structor formula of phenylephrine, a common nasal decongestant;
Class identifiers
Use	; Decongestant, Hypotension, Bradycardia, Hypothermia etc.
ATC code	N07
Biological target	; Alpha adrenergic receptors of the α subtype
External links
MeSH	D000316
	In Wikidata

Adrenergic alpha-agonists (or alpha-adrenergic agonists) are a class of sympathomimetic agents that selectively stimulates alpha adrenergic receptors. The alpha-adrenergic receptor has two subclasses α₁ and α₂. Alpha 2 receptors are associated with sympatholytic properties. α Adrenergic agonists have the opposite function of alpha blockers. Alpha adrenoreceptor ligands mimic the action of epinephrine and norepinephrine signaling in the heart, smooth muscle and central nervous system, with norepinephrine being the highest affinity. The activation of α₁ stimulates the membrane bound enzyme phospholipase C, and activation of α₂ inhibits the enzyme adenylate cyclase. Inactivation of adenylate cyclase in turn leads to the inactivation of the secondary messenger cyclic adenosine monophosphate and induces smooth muscle and blood vessel constriction.

Classes[edit]

Norepinephrine (noradrenaline)

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

α₁ agonist[edit]

α₁ agonist: stimulates phospholipase C activity. (vasoconstriction and mydriasis; used as vasopressors, nasal decongestants and during eye exams). Selected examples are:

Methoxamine

Midodrine

Oxymetazoline

Metaraminol

Phenylephrine ^[1]

α₂ agonist[edit]

α₂ agonist: inhibits adenylyl cyclase activity, reduces brainstem vasomotor center-mediated CNS activation; used as antihypertensive, sedative & treatment of opiate dependence and alcohol withdrawal symptoms). Selected examples are:

Clonidine (mixed alpha2-adrenergic and imidazoline-I1 receptor agonist)

Guanfacine,^[2] (preference for alpha2A-subtype of adrenoceptor)

Guanabenz (most selective agonist for alpha2-adrenergic as opposed to imidazoline-I1)

Guanoxabenz (metabolite of guanabenz)

Guanethidine (peripheral alpha2-receptor agonist)

Xylazine,^[3]

Tizanidine

Medetomidine

Methyldopa

Methylnorepinephrine

Fadolmidine

Dexmedetomidine

Undetermined/unsorted[edit]

The following agents are also listed as agonists by MeSH.^[4]

amidephrine

amitraz

anisodamine

apraclonidine

brimonidine

cirazoline

detomidine

dexmedetomidine

epinephrine

ergotamine

etilefrine

indanidine

lofexidine

medetomidine

mephentermine

metaraminol

methoxamine

mivazerol

naphazoline

norepinephrine

norfenefrine

octopamine

oxymetazoline

phenylpropanolamine

propylhexedrine

rilmenidine

romifidine

synephrine

talipexole

Clinical significance[edit]

Alpha-adrenergic agonists, more specifically the auto receptors of alpha 2 neurons, are used in the treatment of glaucoma by decreasing the production of aqueous fluid by the ciliary bodies of the eye and also by increasing uveoscleral outflow. Medications such as clonidine target pre-synaptic auto receptors, therefore leading to an overall of decrease in norepinephrine.

References[edit]

^ Declerck I, Himpens B, Droogmans G, Casteels R (September 1990). "The alpha 1-agonist phenylephrine inhibits voltage-gated Ca2(+)-channels in vascular smooth muscle cells of rabbit ear artery". Pflügers Arch. 417 (1): 117–9. doi:10.1007/BF00370780. PMID 1963492..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}

^ Sagvolden T (2006). "The alpha-2A adrenoceptor agonist guanfacine improves sustained attention and reduces overactivity and impulsiveness in an animal model of Attention-Deficit/Hyperactivity Disorder (ADHD)". Behav Brain Funct. 2: 41. doi:10.1186/1744-9081-2-41. PMC 1764416. PMID 17173664.

^ Atalik KE, Sahin AS, Doğan N (April 2000). "Interactions between phenylephrine, clonidine and xylazine in rat and rabbit aortas". Methods Find Exp Clin Pharmacol. 22 (3): 145–7. PMID 10893695.

^ MeSH list of agents 82000316

External links[edit]

Adrenergic+alpha-Agonists at the US National Library of Medicine Medical Subject Headings (MeSH)

[pmid1963492-1] Declerck I, Himpens B, Droogmans G, Casteels R (September 1990). "The alpha 1-agonist phenylephrine inhibits voltage-gated Ca2(+)-channels in vascular smooth muscle cells of rabbit ear artery". Pflügers Arch. 417 (1): 117–9. doi:10.1007/BF00370780. PMID 1963492..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}

[pmid17173664-2] Sagvolden T (2006). "The alpha-2A adrenoceptor agonist guanfacine improves sustained attention and reduces overactivity and impulsiveness in an animal model of Attention-Deficit/Hyperactivity Disorder (ADHD)". Behav Brain Funct. 2: 41. doi:10.1186/1744-9081-2-41. PMC 1764416. PMID 17173664.

[pmid10893695-3] Atalik KE, Sahin AS, Doğan N (April 2000). "Interactions between phenylephrine, clonidine and xylazine in rat and rabbit aortas". Methods Find Exp Clin Pharmacol. 22 (3): 145–7. PMID 10893695.

[4] MeSH list of agents 82000316

v t e Adrenergic receptor modulators
α₁	Agonists: 6-FNE Amidephrine Anisodine Buspirone Cirazoline Corbadrine Desglymidodrine Dexisometheptene Dipivefrine Dopamine Droxidopa (L-DOPS) Ephedrine Epinephrine Etilefrine Etilevodopa Ethylnorepinephrine Indanidine Isometheptene L-DOPA (levodopa) L-Phenylalanine L-Tyrosine Melevodopa Metaraminol Methoxamine Methyldopa Midodrine Naphazoline Norepinephrine Octopamine (drug) Oxymetazoline Phenylephrine Phenylpropanolamine Pseudoephedrine Synephrine Tetryzoline Tiamenidine XP21279 Xylometazoline Antagonists: Abanoquil Adimolol Ajmalicine Alfuzosin Amosulalol Anisodamine Arotinolol Atiprosin Atypical antipsychotics (e.g., brexpiprazole, clozapine, olanzapine, quetiapine, risperidone) Benoxathian Buflomedil Bunazosin Carvedilol Corynanthine Dapiprazole Domesticine Doxazosin Ergolines (e.g., ergotamine, dihydroergotamine, lisuride, terguride) Etoperidone Eugenodilol Fenspiride Hydroxyzine Indoramin Ketanserin L-765,314 Labetalol mCPP Mepiprazole Metazosin Monatepil Moxisylyte Naftopidil Nantenine Neldazosin Niaprazine Nicergoline Niguldipine Pardoprunox Pelanserin Perlapine Phendioxan Phenoxybenzamine Phentolamine Phenylpiperazine antidepressants (e.g., hydroxynefazodone, nefazodone, trazodone, triazoledione) Piperoxan Prazosin Quinazosin Quinidine Ritanserin Silodosin Spiperone Talipexole Tamsulosin Terazosin Tiodazosin Tolazoline Tetracyclic antidepressants (e.g., amoxapine, maprotiline, mianserin) Tricyclic antidepressants (e.g., amitriptyline, clomipramine, doxepin, imipramine, trimipramine) Trimazosin Typical antipsychotics (e.g., chlorpromazine, fluphenazine, loxapine, thioridazine) Urapidil WB-4101 Zolertine
α₂	Agonists: (R)-3-Nitrobiphenyline 4-NEMD 6-FNE Amitraz Apraclonidine Brimonidine Cannabivarin Clonidine Corbadrine Detomidine Dexmedetomidine Dihydroergotamine Dipivefrine Dopamine Droxidopa (L-DOPS) Etilevodopa Ephedrine Ergotamine Epinephrine Etilefrine Ethylnorepinephrine Guanabenz Guanfacine Guanoxabenz L-DOPA (levodopa) L-Phenylalanine L-Tyrosine Lofexidine Medetomidine Melevodopa Methyldopa Mivazerol Naphazoline Norepinephrine Oxymetazoline Phenylpropanolamine Piperoxan Pseudoephedrine Rezatomidine Rilmenidine Romifidine Talipexole Tasipimidine Tetrahydrozoline Tiamenidine Tizanidine Tolonidine Urapidil Vatinoxan XP21279 Xylazine Xylometazoline Antagonists: 1-PP Adimolol Amesergide Aptazapine Atipamezole Atypical antipsychotics (e.g., asenapine, brexpiprazole, clozapine, lurasidone, paliperidone, quetiapine, risperidone, zotepine) Azapirones (e.g., buspirone, gepirone, ipsapirone, tandospirone) BRL-44408 Buflomedil Cirazoline Efaroxan Esmirtazapine Fenmetozole Fluparoxan Idazoxan mCPP Mianserin Mirtazapine NAN-190 Olanzapine Pardoprunox Phentolamine Phenoxybenzamine Piperoxan Piribedil Rauwolscine Rotigotine SB-269970 Setiptiline Spiroxatrine Sunepitron Tolazoline Typical antipsychotics (e.g., chlorpromazine, fluphenazine, loxapine, thioridazine) Yohimbine
β	Agonists: Abediterol Alifedrine Amibegron Arbutamine Arformoterol Arotinolol BAAM Bambuterol Befunolol Bitolterol Broxaterol Buphenine Carbuterol Carmoterol Cimaterol Clenbuterol Colterol Corbadrine Denopamine Dipivefrine Dobutamine Dopamine Dopexamine Droxidopa (L-DOPS) Ephedrine Epinephrine Etafedrine Etilefrine Etilevodopa Ethylnorepinephrine Fenoterol Formoterol Hexoprenaline Higenamine Indacaterol Isoetarine Isoprenaline Isoxsuprine L-DOPA (levodopa) L-Phenylalanine L-Tyrosine Levosalbutamol Mabuterol Melevodopa Methoxyphenamine Methyldopa Mirabegron Norepinephrine Orciprenaline Oxyfedrine PF-610355 Phenylpropanolamine Pirbuterol Prenalterol Ractopamine Procaterol Pseudoephedrine Reproterol Rimiterol Ritodrine Salbutamol Salmeterol Solabegron Terbutaline Tretoquinol Tulobuterol Vilanterol Xamoterol XP21279 Zilpaterol Zinterol Antagonists: Acebutolol Adaprolol Adimolol Afurolol Alprenolol Alprenoxime Amosulalol Ancarolol Arnolol Arotinolol Atenolol Befunolol Betaxolol Bevantolol Bisoprolol Bopindolol Bornaprolol Brefonalol Bucindolol Bucumolol Bufetolol Bufuralol Bunitrolol Bunolol Bupranolol Butaxamine Butidrine Butofilolol Capsinolol Carazolol Carpindolol Carteolol Carvedilol Celiprolol Cetamolol Cicloprolol Cinamolol Cloranolol Cyanopindolol Dalbraminol Dexpropranolol Diacetolol Dichloroisoprenaline Dihydroalprenolol Dilevalol Diprafenone Draquinolol Ecastolol Epanolol Ericolol Ersentilide Esatenolol Esprolol Eugenodilol Exaprolol Falintolol Flestolol Flusoxolol Hydroxycarteolol Hydroxytertatolol ICI-118,551 Idropranolol Indenolol Indopanolol Iodocyanopindolol Iprocrolol Isoxaprolol Isamoltane Labetalol Landiolol Levobetaxolol Levobunolol Levomoprolol Medroxalol Mepindolol Metipranolol Metoprolol Moprolol Nadolol Nadoxolol Nebivolol Nifenalol Nipradilol Oxprenolol Pacrinolol Pafenolol Pamatolol Pargolol Penbutolol Pindolol Practolol Primidolol Procinolol Pronethalol Propafenone Propranolol Ridazolol Ronactolol Soquinolol Sotalol Spirendolol SR 59230A Sulfinalol Talinolol Tazolol Tertatolol Tienoxolol Tilisolol Timolol Tiprenolol Tolamolol Toliprolol Xibenolol Xipranolol

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