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An adrenergic alpha-agonist (or alpha-adrenergic agonist) is a drug which selectively stimulates alpha adrenergic receptors. The alpha-adrenergic receptor has two subclasses α1 and α2.
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Classes
Although complete selectivity between receptor agonism is rarely achieved, some agents have partial selectivity.
α1 agonists
α1 agonists: stimulates phospholipase C activity. (vasoconstriction and mydriasis; used as vasopressors, nasal decongestants & eye exams). Selected examples are:
α2 agonists
α2 agonists: inhibits adenylyl cyclase activity. (reduce brainstem vasomotor center-mediated SNS activation; used as antihypertensives, sedatives & treatment of opiate & 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 (periferal alpha2-receptor agonist)
- Xylazine,[3]
- Methyldopa
Undetermined/unsorted
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
- 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.
References
- ^ 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". Pflugers Arch. 417 (1): 117–9. PMID 1963492.
- ^ 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:. PMID 17173664. PMC:1764416.
- ^ 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
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Wikipedia content modification information:
- This page was last modified on 19 July 2008, at 20:58.
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