Aripiprazole

Aripiprazole is a novel and atypical antipsychotic [1].

Aripiprazole has been found to be a dopamine-serotonin system stabilizer with potent partial agonist activity at dopamine D2 and 5-HT1A receptors and antagonist activity at 5-HT2A receptors. In addition, aripiprazole has been reported to label with the agonist [125I]7-OH-PIPAT and with the antagonist [3H]spiperone with 0.34±0.02nM and 0.70±0.22nM, respectively. Besides, aripiprazole has been revealed to dose-dependently and potently inhibit the increase in cAMP accumulation stimulated by forskolin in CHO cells and HEK-293 cells. Other results have also been reported that aripiprazole completely inhibited the increase GTPase activity stimulated by the D2 receptor agonist quinpirole in rat striatal membranes [1].

References:
[1] Burris KD1, Molski TF, Xu C, Ryan E, Tottori K, Kikuchi T, Yocca FD, Molinoff PB. Aripiprazole, a novel antipsychotic, is a high-affinity partial agonist at human dopamine D2 receptors. J Pharmacol Exp Ther. 2002 Jul; 302(1):381-9.

Classics in Chemical Neuroscience: Aripiprazole.[Pubmed:28368577]

ACS Chem Neurosci. 2017 Jun 21;8(6):1135-1146.

Aripiprazole was the first antipsychotic developed to possess agonist properties at dopamine D2 autoreceptors, a groundbreaking strategy that presented a new vista for schizophrenia drug discovery. The dopamine D2 receptor is the crucial target of all extant antipsychotics, and all developed prior to Aripiprazole were D2 receptor antagonists. Extensive blockade of these receptors, however, typically produces extrapyramidal (movement) side effects, which plagued first-generation antipsychotics, such as haloperidol. Second-generation antipsychotics, such as clozapine, with unique polypharmacology and D2 receptor binding kinetics, have significantly lower risk of movement side effects but can cause myriad additional ones, such as severe weight gain and metabolic dysfunction. Aripiprazole's polypharmacology, characterized by its unique agonist activity at dopamine D2 and D3 and serotonin 5-HT1A receptors, as well as antagonist activity at serotonin 5-HT2A receptors, translates to successful reduction of positive, negative, and cognitive symptoms of schizophrenia, while also mitigating risk of weight gain and movement side effects. New observations, however, link Aripiprazole to compulsive behaviors in a small group of patients, an unusual side effect for antipsychotics. In this review, we discuss the chemical synthesis, pharmacology, pharmacogenomics, drug metabolism, and adverse events of Aripiprazole, and we present a current understanding of Aripiprazole's neurotherapeutic mechanisms, as well as the history and importance of Aripiprazole to neuroscience.

Reducing the rehospitalization risk after a manic episode: A population based cohort study of lithium, valproate, olanzapine, quetiapine and aripiprazole in monotherapy and combinations.[Pubmed:28364619]

J Affect Disord. 2017 Aug 1;217:16-23.

BACKGROUND: Data on real-world rehospitalization risks in patients using different drugs and combination therapies for relapse prevention after a manic episode is limited. METHODS: We conducted a nationwide population based cohort study using data from Swedish national registers. Swedish residents aged 18-75 years who were hospitalized for a manic episode between July 1, 2006 and December 2, 2014 were included. Prescription fills of lithium, valproate, olanzapine, quetiapine and Aripiprazole were recorded throughout the first four weeks after hospital discharge, after which the patients were followed for up to one year. General and treatment specific rehospitalization risks were determined and results were adjusted for clinical and sociodemographic factors. RESULTS: The study included follow-up data from 6 502 hospitalizations for mania. Pharmacologic relapse prevention was used after 78% of these hospitalizations. Monotherapies and combination therapies were equally common. The average one-year rehospitalization risk for patients who did versus did not initiate prophylactic treatment was 39% and 46%, respectively. The lowest rehospitalization risks were seen in patients on combination therapy with olanzapine and valproate or olanzapine and lithium, experiencing one year rehospitalization risks of 32% and 34% (adjusted hazard ratios 0.76 (95% confidence interval [CI] 0.62-0.93) and 0.83 (95% CI 0.70-0.98), compared to lithium monotherapy). LIMITATIONS: Register data does not provide information on all clinical parameters affecting treatment choices. CONCLUSIONS: One-year rehospitalization rates after a manic episode are considerable also for patients who initiate prophylactic treatment. Combination therapies including olanzapine and a classic mood-stabilizer may be beneficial for reducing rehospitalization risks after a manic episode.

Effect of combined administration of aripiprazole and fluoxetine on cognitive functions in female rats exposed to ethyl alcohol.[Pubmed:28379219]

Acta Neurobiol Exp (Wars). 2017;77(1):86-93.

Alcoholism is a chronic and recurrent disease. The studies on ethyl alcohol show a progressive deterioration of cognitive functions (motor hyperactivity, operating memory). The aim of the study was to establish whether combined single and chronic administration of Aripiprazole (ARI) and fluoxetine (FLU) affects animal locomotor activity or modifies spatial memory functions in female rats exposed to ethyl alcohol. Female Wistar rats were studied in the Morris Water Maze (MWM) and locomotor activity test. Rats undergoing the MWM and locomotor activity test were injected with saline on day 1, 7, 14 and 21 of testing. Results showed a statistically significant mobility increase in the group of ethanolexposed females (CEt) (21 days) compared to the non-ethanol-exposed group (CNEt). Upon ARI administration to CEt, no statistically significant differences in animal mobility were found, either upon single or chronic administration. Chronic administration of FLU (21 days) as well as combined administration of ARI+FLU (14 and 21 days) caused a statistically significant reduction of the females' mobility compared to the control CEt group. Single and chronic administration of ARI (7x) both show a spatial memory improvement in CEt. No memory improvement was observed, however, after 14 and 21 days of ARI administration. FLU, likewise, improved spatial memory both upon single and chronic administration. Combined administration of ARI+FLU improved memory in CEt only upon single administration. Lack of effect upon chronic administration may be due to tolerance to memory improvement developing upon combined administration of ARI+FLU. It can be concluded that ARI (1.5 mg/kg), FLU (5 mg/kg), and combined administration of these drugs improves spatial memory in CEt.

Rationale and design of the PLACID study: a randomised trial comparing the efficacy and safety of inhaled loxapine versus IM aripiprazole in acutely agitated patients with schizophrenia or bipolar disorder.[Pubmed:28376877]

BMC Psychiatry. 2017 Apr 4;17(1):126.

BACKGROUND: The management of acute agitation manifesting in patients with schizophrenia or bipolar disorder requires swift pharmacological intervention to provide rapid symptomatic relief and prevent escalation to aggression and violence. Antipsychotic medications are widely used in this setting and the availability of an inhaled formulation with deep lung absorption of the antipsychotic loxapine has the potential to deliver a faster onset of therapeutic effect than the available intramuscular formulations of antipsychotics. METHODS: The efficacy of inhaled loxapine and the alternative antipsychotic Aripiprazole delivered via intramuscular (IM) injection will be compared in the Phase IIIb PLACID study. Adults (18-65 years) with a confirmed diagnosis of schizophrenia or bipolar I disorder presenting with acute agitation will be randomly assigned to open-label treatment in a 1:1 ratio. Clinical evaluation will be conducted by raters blinded to treatment assignment. The primary efficacy endpoint is time to response (defined as a Clinical Global Impression of Improvement [CGI-I] score of 1 [very much improved] or 2 [much improved]). Secondary endpoints will include the percentage of responders at different time points after dosing; the proportion of patients who receive 1 or 2 doses of study drug; time to second dose; time to rescue medication; satisfaction with study drug (evaluated using Item 14 of the Treatment Satisfaction Questionnaire for Medication); and safety and tolerability. Approximately 360 patients will be recruited with an interim analysis conducted once 180 patients have completed the study to decide whether to stop for futility or continue with or without an increase in the sample size up to additional 288 patients. DISCUSSION: The PLACID trial will assess the efficacy and safety of inhaled loxapine with deep lung absorption compared with the IM antipsychotic, Aripiprazole, in acutely agitated patients with schizophrenia or bipolar disorder. In the event that the median time to response of inhaled loxapine is significantly shorter than that of the intramuscular Aripiprazole, the PLACID study has the potential to support the inhaled antipsychotic therapy as the standard of care in this setting. TRIAL REGISTRATION: The study protocol was registered with the European Clinical Trials Database on the 31 October 2014 (EudraCT number 2014-000456-29 ).

Usefulness of the dopamine system-stabilizer aripiprazole for reducing morphine-induced emesis.[Pubmed:17678644]

Eur J Pharmacol. 2007 Sep 10;570(1-3):108-10.

In the management of pain, nausea and vomiting are some of the most distressing adverse effects induced by opioids. In the present study, we investigated the effect of the dopamine system-stabilizer Aripiprazole on morphine-induced emesis. Morphine induced retching and vomiting in a dose-dependent manner in ferrets. The emetic effect of morphine was significantly suppressed by pretreatment with either the dopamine receptor antagonist haloperidol or Aripiprazole. These results suggest that the co-administration of Aripiprazole may be useful for reducing the severity of morphine-induced emesis.

Aripiprazole: a novel atypical antipsychotic drug with a uniquely robust pharmacology.[Pubmed:15592581]

CNS Drug Rev. 2004 Winter;10(4):317-36.

Aripiprazole (Abilify) is an atypical antipsychotic drug that has been recently introduced for clinical use in the treatment of schizophrenia. Aripiprazole has a unique pharmacologic profile that includes partial agonism at several G-protein coupled receptors (GPCRs) [especially dopamine (D2) and 5-HT1A] and antagonistic action at others (especially 5-HT2A). Clinical trials indicate that Aripiprazole is effective in treating the positive and negative symptoms of schizophrenia. In short-term studies rapid onset of action (within one week) has been demonstrated. Preliminary data indicate that Aripiprazole may also be effective in the treatment of manic symptoms of bipolar disorder. At recommended doses, Aripiprazole appears to be safe and well tolerated in most adult patients with schizophrenia and schizoaffective disorder. There is only limited information available on the use of Aripiprazole in children and adolescents, and pilot data suggest that a revised dosing strategy, based on weight, is indicated in this population. In the long-term studies, the use of Aripiprazole was associated with continued efficacy, good compliance and increased time-to-relapse. Aripiprazole represents the first functionally selective atypical antipsychotic drug.