Aripiprazole

Aripiprazole

Systematic (IUPAC) name
7-{4-[4-(2,3-Dichlorophenyl)piperazin-1-yl]butoxy}-3,4-dihydroquinolin-2(1H)-one
Clinical data
Trade names	Abilify
AHFS/Drugs.com	monograph
MedlinePlus	a603012
Licence data	EMA:Link, US FDA:link
Pregnancy cat.	C (USA)
Legal status	℞ Prescription only
Routes	Oral (via tablets, orodispersable tablets, and oral solution); intramuscular
Pharmacokinetic data
Bioavailability	87%
Protein binding	>99%
Metabolism	liver
Half-life	75 hours (active metabolite is 94 hours)
Excretion	Feces and urine
Identifiers
CAS number	129722-12-9 Y
ATC code	N05AX12
PubChem	CID 60795
IUPHAR ligand	34
DrugBank	DB01238
ChemSpider	54790 Y
UNII	82VFR53I78 Y
KEGG	D01164 Y
ChEBI	CHEBI:31236 Y
ChEMBL	CHEMBL1112 Y
Chemical data
Formula	C23H27Cl2N3O2
Mol. mass	448.385
SMILES Clc4cccc(N3CCN(CCCCOc2ccc1c(NC(=O)CC1)c2)CC3)c4Cl
InChI InChI=1S/C23H27Cl2N3O2/c24-19-4-3-5-21(23(19)25)28-13-11-27(12-14-28)10-1-2-15-30-18-8-6-17-7-9-22(29)26-20(17)16-18/h3-6,8,16H,1-2,7,9-15H2,(H,26,29) Y Key:CEUORZQYGODEFX-UHFFFAOYSA-N Y
N (what is this?)  (verify)

Aripiprazole (pron.: /ˌɛərɨˈpɪprəzoʊl/ AIR-i-PIP-rə-zohl; brand names: Abilify, Aripiprex) is a partial dopamine agonist of the second generation class of atypical antipsychotics with additional antidepressant properties that is used in the treatment of schizophrenia, bipolar disorder, and clinical depression. It was approved by the U.S. Food and Drug Administration (FDA) for schizophrenia on November 15, 2002 and the European Medicines Agency on 4 June 2004; for acute manic and mixed episodes associated with bipolar disorder on October 1, 2004; as an adjunct for major depressive disorder on November 20, 2007; and to treat irritability in children with autism on 20 November 2009. Aripiprazole was developed by Otsuka in Japan, and in the United States, Otsuka America markets it jointly with Bristol-Myers Squibb.

Medical uses

Aripiprazole is used for the treatment of schizophrenia or bipolar disorder.

In the United States, the FDA has approved aripiprazole for the treatment of schizophrenia in adults and adolescents (aged 13–17), of manic and mixed episodes associated with Bipolar I Disorder with or without psychotic features in adults, children and adolescents (aged 10–17), of irritability associated with autism in pediatric patients (aged 6–17), and of depression when used along with antidepressants in adults.

Aripiprazole is also used off-label for schizophrenia in children (aged 10–12), and to treat dementia-related psychosis in geriatric patients, though Bristol-Myers Squibb was penalized for promoting such uses in the United States.

Bipolar disorder

Aripiprazole has been approved by the FDA for the treatment of acute manic and mixed episodes, in both pediatric patients aged 10–17 and in adults. Several double-blind, placebo-controlled trials support this use. In addition, it is often used as maintenance therapy, either on its own or in conjunction with a mood stabilizer such as lithium or valproate. This use is also supported by a handful of studies. Aripiprazole is at least as effective as haloperidol at reducing manic symptoms, and is much better tolerated by patients.

Aripiprazole's use as a monotherapy in bipolar depression is more controversial. While a few pilot studies have found some effectiveness (with one finding a reduction in anhedonia symptoms), two large, double-blind, placebo-controlled studies found no difference between aripiprazole and placebo. One study reported depression as a side effect of the drug.

Major depression

In 2007, aripiprazole was approved by the FDA for the treatment of unipolar depression when used adjunctively with an antidepressant medication. It has not been FDA-approved for use as monotherapy in unipolar depression.

Autism

In 2009, the United States FDA approved aripiprazole to treat irritability in "children and adolescents ages 6 to 17 years old" who have been diagnosed with autism. It was approved on the basis of two studies that showed it reduced aggression towards others, self-injury, quickly changing moods, and irritability.

Cocaine dependency

Perhaps owing to its mechanism of action relating to dopamine receptors, there is some evidence to suggest that aripiprazole blocks cocaine-seeking behavior in animal models without significantly affecting other rewarding behaviors (such as food self-administration).

Methamphetamine dependency

The book Addiction Medicine mentions studies, suggesting aripiprazole would be counter-therapeutic as treatment for methamphetamine dependency because it increased methamphetamine's stimulant and euphoric effects, and increased the baseline level of desire for methamphetamine. The author mentions studies that suggest that dopamine agonist treatment would be counter-therapeutic for methamphetamine/amphetamine dependency.

Side effects

Common side effects in adults

• nausea
• vomiting
• constipation
• headache
• dizziness
• inner sense of restlessness/need to move (akathisia)
• anxiety
• insomnia
• restlessness

Common side effects in children

• feeling sleepy
• headache
• vomiting
• fatigue
• increased appetite
• insomnia
• nausea
• stuffy nose
• weight gain
• uncontrolled movement such as restlessness, tremor muscle stiffness

Infrequent

• Uncontrollable twitching or jerking movements, tremors, seizure, and weight gain. Some people may feel dizzy, especially when getting up from a lying or sitting position, or may experience a fast heart rate.
• Neuroleptic malignant syndrome (Combination of fever, muscle stiffness, faster breathing, sweating, reduced consciousness, and sudden change in blood pressure and heart rate.)
• Suicidal thoughts and suicide attempts
• Painful and/or sustained erection (Priapism)
• Tardive dyskinesia (As with all antipsychotic medication, patients using aripiprazole may develop the permanent neurological disorder tardive dyskinesia.)
• Stroke (While taking aripiprazole some elderly patients with dementia have suffered from stroke or 'mini' stroke.)
• Allergic reaction (such as swelling in the mouth or throat, itching, rash), speech disorder, nervousness, agitation, fainting, reports of abnormal liver test values, inflammation of the pancreas, muscle pain, weakness, stiffness, or cramps.
• Sudden unexplained death

Discontinuation

Aripiprazole should be discontinued gradually, with careful consideration from the prescribing doctor, to avoid withdrawal symptoms or relapse.

The British National Formulary recommends a gradual withdrawal when discontinuing anti-psychotic treatment to avoid acute withdrawal syndrome or rapid relapse. Due to compensatory changes at dopamine, serotonin, adrenergic and histamine receptor sites in the central nervous system, withdrawal symptoms can occur during abrupt or over-rapid reduction in dosage. Withdrawal symptoms reported to occur after discontinuation of antipsychotics include nausea, emesis, lightheadedness, diaphoresis, dyskinesia, orthostatic hypotension, tachycardia, nervousness, dizziness, headache, excessive non-stop crying, and anxiety. Some have argued that additional somatic and psychiatric symptoms associated with dopaminergic super-sensitivity, including dyskinesia and acute psychosis, are common features of withdrawal in individuals treated with neuroleptics. This has led some to suggest that the withdrawal process might itself be schizo-mimetic, producing schizophrenia-like symptoms even in previously healthy patients, indicating a possible pharmacological origin of mental illness in a yet unknown percentage of patients currently and previously treated with antipsychotics. This question is unresolved, and remains a highly controversial issue among professionals in the medical and mental health communities, as well the public. Complicated and long-lasting rebound insomnia symptoms can also occur after withdrawing from antipsychotics.^{[citation needed]}

Overdosage

Children or adults who ingested acute overdoses have usually manifested central nervous system depression ranging from mild sedation to coma; serum concentrations of aripiprazole and dehydroaripiprazole in these patients were elevated by up to 3-4 fold over normal therapeutic levels, yet to date no deaths have been recorded.

Drug interactions

Aripiprazole is a substrate of CYP2D6 and CYP3A4. Coadministration with medications that inhibit (e.g. paroxetine, fluoxetine) or induce (e.g. carbamazepine) these metabolic enzymes are known to increase and decrease, respectively, plasma levels of aripiprazole. As such, anyone taking aripiprazole should be aware that their dosage of aripiprazole may need to be decreased.

Aripiprazole may change the subjective effects of alcohol. One study found that aripiprazole increased the sedative effect and reduced the sense of euphoria normally associated with alcohol consumption. However, another alcohol study found that there was no difference in subjective effect between a placebo group and a group taking aripiprazole.

Pharmacology

Binding profile

Aripiprazole acts as an antagonist/inverse agonist (unless otherwise noted) of the following receptors and transporters:

5-HT1A receptor (Ki = 1.7 nM) (partial agonist) 5-HT2A receptor (Ki = 3.4 nM) 5-HT2C receptor (Ki = 15 nM) (partial agonist) 5-HT7 receptor (Ki = 39 nM) D2 receptor (Ki = 0.34 nM) (partial agonist) D3 receptor (Ki = 0.8 nM) D4 receptor (Ki = 44 nM) α1-adrenergic receptor (Ki = 57 nM) H1 receptor (Ki = 61 nM) 5-HT transporter (Ki = 98 nM)

Aripiprazole's mechanism of action is different from those of the other FDA-approved atypical antipsychotics (e.g., clozapine, olanzapine, quetiapine, ziprasidone, and risperidone). Rather than antagonizing the D₂ receptor, aripiprazole acts as a D₂ partial agonist. Aripiprazole is also a partial agonist at the 5-HT_1A receptor, and like the other atypical antipsychotics displays an antagonist profile at the 5-HT_2A receptor. It also antagonizes the 5-HT₇ receptor and acts as a partial agonist at the 5-HT_2C receptor, both with high affinity. The latter action may underlie the minimal weight gain seen in the course of therapy. Aripiprazole has moderate affinity for histamine, α-adrenergic, and D4 receptors as well as the serotonin transporter, while it has no appreciable affinity for cholinergic muscarinic receptors.

D₂ and D₃ receptor occupancy levels are high, with average levels ranging between ~71% at 2 mg/day to ~96% at 40 mg/day. Most atypical antipsychotics bind preferentially to extrastriatal receptors, but aripiprazole appears to be less preferential in this regard, as binding rates are high throughout the brain.

Recently, it has been demonstrated that in 5-HT₇ receptor knockout mice, aripiprazole does not reduce immobility time in the forced swim test (FST), and actually increases it. This implicates 5-HT₇ antagonism as playing a major role in aripiprazole's antidepressant effects, similarly to amisulpride. Note, however, humans possess a splice variant not found in lower mammals (the "d" isoform), while mice possess one not found in humans (the "c"). The significantly altered c-terminus observed in 5-HT_7(d) results in a similar binding affinity to the other forms of this receptor, however, the "c" variant found in lower mammals differs in affinity. This difference in expression means the receptor's function in modulating thalamic and hypothalamic output, and corresponding effect on fatigue perception and alertness may not be homologous in mice and humans.

Aripiprazole produces 2,3-dichlorophenylpiperazine (DCPP) as a metabolite similarly to how trazodone and nefazodone reduce to 3-chlorophenylpiperazine (mCPP) and niaprazine converts to 4-fluorophenylpiperazine (pFPP). It is unknown whether DCPP contributes to aripiprazole's pharmacology.^{[citation needed]}

Pharmacokinetics

Aripiprazole displays linear kinetics and has an elimination half-life of approximately 75 hours. Steady-state plasma concentrations are achieved in about 14 days. C_max (maximum plasma concentration) is achieved 3–5 hours after oral dosing. Bioavailability of the oral tablets is about 90% and the drug undergoes extensive hepatic metabolization (dehydrogenation, hydroxylation, and N-dealkylation), principally by the enzymes CYP2D6 and CYP3A4. Its only known active metabolite is dehydro-aripiprazole, which typically accumulates to approximately 40% of the aripiprazole concentration. The parenteral drug is excreted only in traces, and its metabolites, active or not, are excreted via feces and urine. When dosed daily, brain concentrations of aripiprazole will increase for a period of 10–14 days, before reaching stable constant levels.^{[citation needed]}

Patent status

Otsuka's US patent on aripiprazole expires on October 20, 2014; however, due to a pediatric extension, a generic will not become available until at least April 20, 2015. Barr Laboratories (now Teva Pharmaceuticals) initiated a patent challenge under the Hatch-Waxman Act in March 2007. On November 15, 2010, this challenge was rejected by a United States district court in New Jersey.[1][2]

Dosage forms

Abilify 2mg tablets (US)

• Intramuscular injection, solution: 9.75 mg/mL (1.3 mL)
• Solution, oral: 1 mg/mL (150 mL) [contains propylene glycol, sucrose 400 mg/mL, and fructose 200 mg/mL; orange cream flavor]
• Tablet: 2 mg, 5 mg, 10 mg, 15 mg, 20 mg, 30 mg
• Tablet, orally disintegrating: 10 mg [contains phenylalanine 1.12 mg; creme de vanilla flavor]; 15 mg [contains phenylalanine 1.68 mg; creme de vanilla flavor]

Synthesis

Aripiprazole can be synthesized beginning with a dichloroaniline and bis(2-chloroethyl)amine:

References

Aripiprazole-induced oculogyric crisis (acute dystonia).Jyotik T Bhachech.Journal of Pharmacology and Pharmacotherapeutics. Jul-Sept 2012,3:279-81.http://www.jpharmacol.com/article.asp?issn=0976-500X;year=2012;volume=3;issue=3;spage=279;epage=281;aulast=Bhachech;type=0

External links

• Abilify website
• Abilify Full Prescribing Information (for Health Care Professionals)
• U.S. National Library of Medicine: Drug Information Portal - Aripiprazole
• Abilify adverse events reported to the FDA
• Mechanism of Action Of Aripiprazole