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Azapirone

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File:Buspirone.svg
Buspirone, the prototypical azapirone anxiolytic, which contains azaspirodecanedione and pyrimidinylpiperazine bound via a butyl chain.

Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics.<ref name="pmid1973936">Template:Cite journal</ref><ref name="pmid8638511">Template:Cite journal</ref><ref name="pmid16856115">Template:Cite journal</ref><ref name="pmid2567039">Template:Cite journal</ref> They are commonly used as add-ons to other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs).<ref>Template:Cite book</ref><ref name="pmid8827420">Template:Cite journal</ref><ref name="pmid9180827">Template:Cite journal</ref><ref name="pmid9864079">Template:Cite journal</ref><ref name="pmid11465522">Template:Cite journal</ref><ref name="pmid12667165">Template:Cite journal</ref>

List of azapironesEdit

The azapirones include the following agents:<ref name="who">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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Anxiolytics
Antipsychotics
others

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Medical usesEdit

Azapirones have shown benefit in general anxiety<ref>Template:Cite journal</ref> and augmenting SSRIs in social anxiety<ref>Template:Cite book</ref> and depression.<ref>Template:Cite journal</ref> Evidence is not clear for panic disorder<ref>Template:Cite journal</ref> and functional gastrointestinal disorders.<ref>Template:Cite journal</ref>

Tandospirone has also been used to augment antipsychotics in Japan as it improves cognitive and negative symptoms of schizophrenia.<ref name="pmid11579010">Template:Cite journal</ref> Buspirone is being investigated for this purpose as well.<ref name="pmid17628435">Template:Cite journal</ref><ref name="pmid19637398">Template:Cite journal</ref>

Side effectsEdit

Side effects of azapirones may include dizziness, headaches, restlessness, nausea, and diarrhea.<ref name="pmid2567039"/><ref name="pmid2870641">Template:Cite journal</ref>

Azapirones have more tolerable adverse effects than many other available anxiolytics, such as benzodiazepines or SSRIs. Unlike benzodiazepines, azapirones lack abuse potential and are not addictive, do not cause cognitive/memory impairment or sedation, and do not appear to induce appreciable tolerance or physical dependence. However, azapirones are considered less effective with slow onset in controlling symptoms.<ref>Template:Cite journal</ref>

ChemistryEdit

Buspirone was originally classified as an azaspirodecanedione, shortened to azapirone or azaspirone due to the fact that its chemical structure contained this moiety, and other drugs with similar structures were labeled as such as well. However, despite all being called azapirones, not all of them actually contain the azapirodecanedione component, and most in fact do not or contain a variation of it. Additionally, many azapirones are also pyrimidinylpiperazines, though again this does not apply to them all.

Drugs classed as azapirones can be identified by their -spirone or -pirone suffix.<ref name="urlThe use of stems in the selection of International Nonproprietary Names (INN) for pharmaceutical substances">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

PharmacologyEdit

PharmacodynamicsEdit

On a pharmacological level, azapirones varyingly possess activity at the following receptors:<ref name="pmid1974152">Template:Cite journal</ref><ref name="pmid1685786">Template:Cite journal</ref><ref name="pmid1361441">Template:Cite journal</ref><ref name="pmid7766287">Template:Cite journal</ref><ref name="pmid11561089">Template:Cite journal</ref><ref name="pmid1975278">Template:Cite journal</ref><ref name="pmid1982326">Template:Cite journal</ref><ref name="pmid17439416">Template:Cite journal</ref>

Actions at D4, 5-HT2C, 5-HT7, and sigma receptors have also been shown for some azapirones.<ref name="pmid8524985">Template:Cite journal</ref><ref name="pmid10991983">Template:Cite journal</ref><ref name="pmid17786406">Template:Cite journal</ref><ref name="pmid1970425">Template:Cite journal</ref>

While some of the listed properties such as 5-HT2A and D2 blockade may be useful in certain indications such as in the treatment of schizophrenia (as with perospirone and tiospirone), all of them except 5-HT1A agonism are generally undesirable in anxiolytics and only contribute to side effects. As a result, further development has commenced to bring more selective of anxiolytic agents to the market. An example of this initiative is gepirone, which was recently approved after completing clinical trials in the United States for the treatment of major depression and generalized anxiety disorder. Another example is tandospirone which has been licensed in Japan for the treatment of anxiety and as an augmentation to antidepressants for depression.

5-HT1A receptor partial agonists have demonstrated efficacy against depression in rodent studies and human clinical trials.<ref name="pmid2883013">Template:Cite journal</ref><ref name="pmid12559651">Template:Cite journal</ref><ref name="pmid2198303">Template:Cite journal</ref><ref name="pmid18373383">Template:Cite journal</ref> Unfortunately, however, their efficacy is limited and they are only relatively mild antidepressants. Instead of being used as monotherapy treatments, they are more commonly employed as augmentations to serotonergic antidepressants like the SSRIs.<ref name="pmid8827420"/><ref name="pmid9180827"/><ref name="pmid9864079"/><ref name="pmid11465522"/><ref name="pmid12667165"/> It has been proposed that high intrinsic activity at 5-HT1A postsynaptic receptors is necessary for maximal therapeutic benefits to come to prominence, and as a result, investigation has commenced in azapirones which act as 5-HT1A receptor full agonists such as alnespirone and eptapirone.<ref name="pmid9765347">Template:Cite journal</ref><ref name="pmid11408031">Template:Cite journal</ref><ref name="pmid12398907">Template:Cite journal</ref><ref name="pmid17803293">Template:Cite journal</ref> Indeed, in preclinical studies, eptapirone produces robust antidepressant effects which surpass those of even high doses of imipramine and paroxetine.<ref name="pmid9765347"/><ref name="pmid11408031"/><ref name="pmid12398907"/><ref name="pmid17803293"/>

Comparison of binding profilesEdit

Affinities of Azapirones for Neurotransmitter Binding Sites (Ki, nM)<ref name="pmid1974152" />
Binding site Buspirone Gepirone Ipsapirone Tandospirone
5-HT1A 20 ± 3 70 ± 10 7.9 ± 2 27 ± 5
5-HT1B > 100,000 > 100,000 > 100,000 > 100,000
5-HT1D > 100,000 > 100,000 33,000 ± 8,000 > 100,000
5-HT2A 1,300 ± 400 3,000 ± 50 6,400 ± 4,000 1,300 ± 200
5-HT2C 1,100 ± 200 5,000 ± 700 5,000 ± 1,000 2,600 ± 60
Template:Abbrlink – – – > 100,000
D1 33,000 ± 1,000 > 100,000 15,000 ± 2,000 41,000 ± 10,000
D2 240 ± 50 2,200 ± 200 1,900 ± 200 1,700 ± 300
α1-Adrenergic 1,000 ± 400 2,300 ± 300 40 ± 7 1,600 ± 80
α2-Adrenergic 6,000 ± 700 1,600 ± 200 1,900 ± 500 1,900 ± 400
β-Adrenergic 8,800 ± 1,000 > 100,000 > 100,000 > 100,000
Template:Abbrlink 38,000 ± 5,000 > 100,000 49,000 ± 5,000 > 100,000
[[GABAA receptor#Benzodiazepine site|GABAA/Template:Abbr]] > 100,000 > 100,000 > 100,000 > 100,000

PharmacokineticsEdit

Azapirones are poorly but nonetheless appreciably absorbed and have a rapid onset of action, but have only very short half-lives ranging from 1–3 hours. As a result, they must be administered 2–3 times a day. The only exception to this rule is umespirone, which has a very long duration with a single dose lasting as long as 23 hours.<ref name="pmid7957544">Template:Cite journal</ref> Unfortunately, umespirone has not been commercialized. Although never commercially produced, Bristol-Myers Squibb applied for a patent on October 28, 1993, and received the patent on July 11, 1995, for an extended release formulation of buspirone.<ref>Template:Cite patent</ref> An extended release formulation of gepirone is currently under development and if approved, should help to improve this issue.

Metabolism of azapirones occurs in the liver and they are excreted in urine and feces. A common metabolite of several azapirones including buspirone, gepirone, ipsapirone, revospirone, and tandospirone is 1-(2-pyrimidinyl)piperazine (1-PP).<ref name="pmid8750726">Template:Cite journal</ref><ref name="pmid1681447">Template:Cite journal</ref><ref name="pmid2149168">Template:Cite journal</ref> 1-PP possesses 5-HT1A partial agonist and α2-adrenergic antagonist actions and likely contributes overall mostly to side effects.<ref name="pmid8750726"/><ref name="pmid1681447"/><ref name="pmid12438536">Template:Cite journal</ref>

ReferencesEdit

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 | group1 = Template:Abbrlink agonists
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 | group2 = Template:Abbrlink Template:Abbrlink
 |  list2 = 

 | group3 = Hypnotics
 | list3 =



 | group4 = Gabapentinoids
([[Voltage-dependent calcium channel#.CE.B12.CE.B4_Subunit|Template:Abbr Template:Abbr]] blockers)
 |  list4 =

 | group5 = Antidepressants
 | list5 = 

 | group6 = Antipsychotics
 | list6 =



 | group7 = Sympatholytics
(Antiadrenergics)
 |  list7 =

 | group8 = Others
 |  list8 =

| list9 = Template:PharmNavFootnote



}} Template:Navbox with collapsible groups Template:Antipsychotics Template:Adrenergics Template:Dopaminergics Template:Serotonergics Template:Sigmaergics Template:Piperazines Template:Chemical classes of psychoactive drugs

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