Azapirones are a class of drugs used as

anxiolytic An anxiolytic (; also antipanic or antianxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiet ...

s, antidepressants, and

antipsychotic Antipsychotics, also known as neuroleptics, are a class of psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but also in a range of ...

s. They are commonly used as add-ons to other antidepressants, such as

selective serotonin reuptake inhibitor Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions. SSRIs increase the extracellul ...

s (SSRIs).

Medical uses

Azapirones have shown benefit in general anxiety and augmenting SSRIs in social anxiety and depression. Evidence is not clear for

panic disorder Panic disorder is a mental and behavioral disorder, specifically an anxiety disorder characterized by reoccurring unexpected panic attacks. Panic attacks are sudden periods of intense fear that may include palpitations, sweating, shaking, short ...

and functional gastrointestinal disorders. Tandospirone has also been used to augment antipsychotics in Japan as it improves cognitive and negative symptoms of

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wit ...

Buspirone Buspirone, sold under the brand name Buspar, among others, is a medication primarily used to treat anxiety disorders, particularly generalized anxiety disorder. Benefits support its short-term use. It is taken by mouth, and it may take up to fo ...

is being investigated for this purpose as well. Gepirone was abandoned after FDA rejection.

Side effects

Side effects of azapirones may include

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...

, headaches, restlessness,

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

, and

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

. Azapirones have more tolerable adverse effects than many other available anxiolytics, such as benzodiazepines or SSRIs. Unlike benzodiazepines, azapirones lack

abuse potential Substance abuse, also known as drug abuse, is the use of a drug in amounts or by methods which are harmful to the individual or others. It is a form of substance-related disorder. Differing definitions of drug abuse are used in public health, ...

and are not addictive, do not cause cognitive/memory impairment or sedation, and do not appear to induce appreciable tolerance or

physical dependence Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms. Physical dependence can develop from low-dose therapeutic use of certai ...

. However, azapirones are considered less effective with slow onset in controlling symptoms.

List of azapirones

The azapirones include the following agents: ; Anxiolytics *

Alnespirone Alnespirone (S-20,499) is a selective 5-HT1A receptor full agonist of the azapirone chemical class. It has antidepressant and anxiolytic effects. See also * 8-OH-DPAT * Azapirone Azapirones are a class of drugs used as anxiolytics, anti ...

(S-20,499) *

Binospirone Binospirone (MDL-73,005-EF) is a drug which acts as a partial agonist at 5-HT1A somatodendritic autoreceptors but as an antagonist at postsynaptic 5-HT1A receptors. It has anxiolytic effects. See also * Azapirone Azapirones are a class of ...

(MDL-73,005) * BMY-7,378 *

(Buspar) *

Enilospirone Enilospirone (CERM-3,726) is a selective 5-HT1A receptor agonist of the azapirone class. See also * Azapirone Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics. They are commonly used as add-ons to ...

(CERM-3,726) *

Eptapirone Eptapirone (F-11,440) is a very potent and highly selective 5-HT1A receptor full agonist of the azapirone family. Its affinity for the 5-HT1A receptor was reported to be 4.8 nM (Ki) (or 8.33 (pKi)), and its intrinsic activity approximately e ...

(F-11,440) *

Gepirone Gepirone is an antidepressant and anxiolytic drug of the azapirone group that was synthesized by Bristol-Myers Squibb in 1986 and has been under development for the treatment of depression but has yet to be marketed. It has been under developmen ...

(Ariza, Variza) *

Ipsapirone Ipsapirone is a selective 5-HT1A receptor partial agonist of the piperazine and azapirone chemical classes. It has antidepressant and anxiolytic effects. Ipsapirone was studied in several placebo-controlled trials for depression and continues ...

(TVX-Q-7,821)
MJ-7378
1103-03-7*

Revospirone Revospirone (Bay Vq 7813) is an azapirone drug which was patented as a veterinary tranquilizer but was never marketed. It acts as a selective 5-HT1A receptor partial agonist. Similarly to other azapirones such as buspirone, revospirone produces ...

(BAY-VQ-7,813) * Tandospirone (Sediel) * Zalospirone (WY-47,846) ; Antipsychotics *

Perospirone Perospirone (Lullan) is an atypical antipsychotic of the azapirone family. It was introduced in Japan by Dainippon Sumitomo Pharma in 2001 for the treatment of schizophrenia and acute cases of bipolar mania. Medical uses Its primary uses are i ...

(Lullan) * Tiospirone (BMY-13,859) *

Umespirone Umespirone (KC-9172) is a drug of the azapirone class which possesses anxiolytic and antipsychotic properties. It behaves as a 5-HT1A receptor partial agonist (Ki = 15 nM), D2 receptor partial agonist (Ki = 23 nM), and α1-adrenoceptor recepto ...

(KC-9,172) ; other
SNAP-8719
55893-38-0

Chemistry

was originally classified as an

azaspirodecanedione Azaspirodecanedione is a chemical compound. It is a component of the chemical structures of several of the azapirones. See also * Azapirone * Azaspirodecane * Glutarimide * Ketone In organic chemistry, a ketone is a functional group w ...

, shortened to azapirone or azaspirone due to the fact that its

chemical structure A chemical structure determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target molecule or other solid. Molecular geometry refers to the spatial arrangement of ...

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.

Pharmacology

Pharmacodynamics

On a

pharmacological Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...

level, azapirones varyingly possess activity at the following receptors: * 5-HT_1A receptor (as partial or

full agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the a ...

s) * 5-HT_2A receptor (as inverse agonists) * D₂ receptor (as antagonists or partial agonists) * α₁-adrenergic receptor (as antagonists) * α₂-adrenergic receptor (as antagonists) Actions at D₄, 5-HT_2C, 5-HT₇, and

sigma receptor Sigma receptors (σ-receptors) are protein cell surface receptors that bind ligands such as 4-PPBP (4-phenyl-1-(4-phenylbutyl) piperidine), SA 4503 (cutamesine), ditolylguanidine, dimethyltryptamine, and siramesine. There are two subtypes, ...

s have also been shown for some azapirones. While some of the listed properties such as 5-HT_2A and D₂ blockade may be useful in certain indications such as in the treatment of

(as with perospirone and tiospirone), all of them except 5-HT_1A agonism are generally undesirable in anxiolytics and only contribute to

side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...

s. 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 is currently in

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, diet ...

s in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

for the treatment of

major depression Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Introdu ...

and

generalized anxiety disorder Generalized anxiety disorder (GAD) is a mental and behavioral disorder, specifically an anxiety disorder characterized by excessive, uncontrollable and often irrational worry about events or activities. Worry often interferes with daily function ...

. Another example is tandospirone which has been licensed in Japan for the treatment of anxiety and as an augmentation to antidepressants for depression. 5-HT_1A receptor partial agonists have demonstrated efficacy against depression in rodent studies and human clinical trials. 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. It has been proposed that high

intrinsic activity Intrinsic activity (IA) and efficacy refer to the relative ability of a drug- receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its mol ...

at 5-HT_1A 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-HT_1A receptor full agonists such as alnespirone and eptapirone. Indeed, in

preclinical studies In drug development, preclinical development, also termed preclinical studies or nonclinical studies, is a stage of research that begins before clinical trials (testing in humans) and during which important feasibility, iterative testing and drug ...

, eptapirone produces robust antidepressant effects which surpass those of even high doses of imipramine and

paroxetine Paroxetine, sold under the brand names Paxil and Seroxat among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used to treat major depressive disorder, obsessive-compulsive disorder, panic disorder ...

Comparison of binding profiles

Pharmacokinetics

Azapirones are poorly but nonetheless appreciably absorbed and have a rapid

onset of action Onset of action is the duration of time it takes for a drug's effects to come to prominence upon administration. With oral administration, it typically ranges anywhere from 20 minutes to over an hour, depending on the drug in question. Other meth ...

, 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. 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. An extended release formulation of gepirone is currently under development and if approved, should help to improve this issue.

Metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

of azapirones occurs in the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

and they are

excreted Excretion is a process in which metabolic waste is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after lea ...

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

and feces. A common metabolite of several azapirones including

buspirone Buspirone, sold under the brand name Buspar, among others, is a medication primarily used to treat anxiety disorders, particularly generalized anxiety disorder. Benefits support its short-term use. It is taken by mouth, and it may take up to fo ...

gepirone Gepirone is an antidepressant and anxiolytic drug of the azapirone group that was synthesized by Bristol-Myers Squibb in 1986 and has been under development for the treatment of depression but has yet to be marketed. It has been under developmen ...

ipsapirone Ipsapirone is a selective 5-HT1A receptor partial agonist of the piperazine and azapirone chemical classes. It has antidepressant and anxiolytic effects. Ipsapirone was studied in several placebo-controlled trials for depression and continues ...

revospirone Revospirone (Bay Vq 7813) is an azapirone drug which was patented as a veterinary tranquilizer but was never marketed. It acts as a selective 5-HT1A receptor partial agonist. Similarly to other azapirones such as buspirone, revospirone produces ...

, and tandospirone is

1-(2-pyrimidinyl)piperazine 1-(2-Pyrimidinyl)piperazine (1-PP, 1-PmP) is a chemical compound and piperazine derivative. It is known to act as an antagonist of the α2-adrenergic receptor (Ki = 7.3–40 nM) and, to a much lesser extent, as a partial agonist of the 5- ...

(1-PP). 1-PP possesses 5-HT_1A partial agonist and α₂-adrenergic antagonist actions and likely contributes overall mostly to side effects.

References

{{Piperazines