View source for Alpha-adrenergic agonist

An '''adrenergic alpha-agonist''' (or '''alpha-adrenergic agonist''') is a drug that selectively stimulates alpha [[adrenergic receptor]]s. The alpha-adrenergic receptor has two subclasses α<sub>1</sub> and α<sub>2</sub>. 

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

===α<sub>1</sub> agonists===
{{Main|Alpha-1 adrenergic receptor#agonists}}

[[alpha-1 receptor|α<sub>1</sub>]] agonists: stimulates phospholipase C activity. (vasoconstriction and mydriasis; used as vasopressors, nasal decongestants and eye exams). Selected examples are:
* [[Methoxamine]] 
* [[Methylnorepinephrine]] 
* [[Oxymetazoline]] 
* [[Phenylephrine]] <ref name="pmid1963492">{{cite journal |author=Declerck I, Himpens B, Droogmans G, Casteels R |title=The alpha 1-agonist phenylephrine inhibits voltage-gated Ca2(+)-channels in vascular smooth muscle cells of rabbit ear artery |journal=Pflugers Arch. |volume=417 |issue=1 |pages=117–9 |year=1990 |month=September |pmid=1963492 |doi= 10.1007/BF00370780|url=}}</ref>

===α<sub>2</sub> agonists===
{{Main|Alpha-2 adrenergic receptor#Agonists}}
[[alpha-2 receptor|α<sub>2</sub>]] agonists: inhibits adenylyl cyclase activity. (reduce brainstem vasomotor center-mediated CNS activation; used as antihypertensives, sedatives & treatment of opiate and [[alcohol withdrawal]] symptoms). Selected examples are:
* [[Clonidine]] (mixed alpha2-adrenergic and imidazoline-I1 receptor agonist)
* [[Guanfacine]],<ref name="pmid17173664">{{cite journal |author=Sagvolden T |title=The alpha-2A adrenoceptor agonist guanfacine improves sustained attention and reduces overactivity and impulsiveness in an animal model of Attention-Deficit/Hyperactivity Disorder (ADHD) |journal=Behav Brain Funct |volume=2 |issue= |pages=41 |year=2006 |pmid=17173664 |pmc=1764416 |doi=10.1186/1744-9081-2-41 |url=http://www.behavioralandbrainfunctions.com/content/2//41}}</ref> (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]],<ref name="pmid10893695">{{cite journal |author=Atalik KE, Sahin AS, Doğan N |title=Interactions between phenylephrine, clonidine and xylazine in rat and rabbit aortas |journal=Methods Find Exp Clin Pharmacol |volume=22 |issue=3 |pages=145–7 |year=2000 |month=April |pmid=10893695 |doi= |url=http://journals.prous.com/journals/servlet/xmlxsl/pk_journals.xml_summaryn_pr?p_JournalId=6&p_RefId=796096}}</ref>
* [[Methyldopa]]
*[[Fadolmidine]]

===Undetermined/unsorted===
The following agents are also listed as agonists by [[Medical Subject Headings|MeSH]].<ref>{{MeshPharmaList|82000316}}</ref>
* [[amidephrine]]
* [[amitraz]]
* [[anisodamine]]
* [[apraclonidine]]
* [[brimonidine]]
* [[cirazoline]]
* [[detomidine]]
* [[dexmedetomidine]]
* [[epinephrine]]
* [[ergotamine]]
* [[etilefrine]]
* [[indanidine]]
* [[lofexidine]]
* [[medetomidine]]
* [[mephentermine]]
* [[metaraminol]]
* [[methoxamine]]
* [[midodrine]]
* [[mivazerol]]
* [[naphazoline]]
* [[norepinephrine]]
* [[norfenefrine]]
* [[octopamine]]
* [[oxymetazoline]]
* [[phenylpropanolamine]]
* [[rilmenidine]]
* [[romifidine]]
* [[synephrine]]
* [[talipexole]]
* [[tizanidine]]

==Clinical significance==
Alpha-adrenergic agonists 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.

==See also==
*[[Alpha blocker]]

==References==
{{reflist}}

==External links==
* {{MeshName|Adrenergic+alpha-Agonists}}

{{Receptor agonists and antagonists}}
{{Adrenergic agonists}}
{{Hypnotics and sedatives}}

[[Category:Alpha-adrenergic agonists| ]]


{{sedative-stub}}
[[Category:2Fix]]