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Aripiprazole, a novel antipsychotic, is a high-affinity partial agonist at human dopamine D2 receptors.

Aripiprazole is the first next-generation atypical antipsychotic with a mechanism of action that differs from currently marketed typical and atypical antipsychotics. Aripiprazole displays properties of an agonist and antagonist in animal models of dopaminergic hypoactivity and hyperactivity, respectively. This study examined the interactions of aripiprazole with a single population of human D2 receptors to clarify further its pharmacologic properties. In membranes prepared from Chinese hamster ovary cells that express recombinant D2L receptors, aripiprazole bound with high affinity to both the G protein-coupled and uncoupled states of receptors. Aripiprazole potently activated D2 receptor-mediated inhibition of cAMP accumulation. Partial receptor inactivation using the alkylating agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) significantly reduced the maximum effect of aripiprazole on inhibition of cAMP accumulation. This effect was seen with concentrations of EEDQ that did not alter the maximal inhibitory effect of dopamine. Consistent with the expected effects of a partial agonist, increasing concentrations of aripiprazole blocked the action of dopamine with maximal blockade equal to the agonist effect of aripiprazole alone. The efficacy of aripiprazole relative to that of dopamine varied from 25% in cells that lacked spare receptors for dopamine to 90% in cells with receptor reserve. These results, together with previous studies demonstrating partial agonist activity at serotonin 5-hydroxytryptamine (5-HT)1A receptors and antagonist activity at 5-HT2A receptors, support the identification of aripiprazole as a dopamine-serotonin system stabilizer. The receptor activity profile may underlie the unique activity of aripiprazole in animals and its antipsychotic activity in humans.

1-Methyl-3-isobutylxanthine↗

Aripiprazole, an antipsychotic with a novel mechanism of action, and risperidone vs placebo in patients with schizophrenia and schizoaffective disorder.

BACKGROUND: Aripiprazole is a dopamine D2 receptor partial agonist with partial agonist activity at serotonin 5HT1A receptors and antagonist activity at 5HT2A receptors. This multicenter trial examined the efficacy, safety, and tolerability of aripiprazole in patients with acute exacerbation of schizophrenia or schizoaffective disorder. METHODS: In this 4-week double-blind study, 404 patients were randomized to 20 mg/d (n = 101) or 30 mg/d (n = 101) of aripiprazole, placebo (n = 103), or 6 mg/d of risperidone (n = 99). Efficacy assessments included Positive and Negative Syndrome Scale (PANSS) scores and Clinical Global Impression scores. Safety and tolerability evaluations included extrapyramidal symptoms and effects on weight, prolactin, and corrected QT (QTc) interval. RESULTS: Aripiprazole (20 and 30 mg/d) and risperidone (6 mg/d) were significantly better than placebo on all efficacy measures. Separation from placebo occurred at week 1 for PANSS total and positive scores with aripiprazole and risperidone and for PANSS negative scores with aripiprazole. There were no significant differences between aripiprazole and placebo in mean change from baseline in the extrapyramidal symptom rating scales. Mean prolactin levels decreased with aripiprazole but significantly increased 5-fold with risperidone. Mean change in QTc interval did not differ significantly from placebo with any active treatment group. Aripiprazole and risperidone groups showed a similar low incidence of clinically significant weight gain. CONCLUSIONS: Aripiprazole is effective, safe, and well tolerated for the positive and negative symptoms in schizophrenia and schizoaffective disorder. It is the first non-D2 receptor antagonist with clear antipsychotic effects and represents a novel treatment development for psychotic disorders.

Adult↗

Aripiprazole in the treatment of schizophrenia: safety and tolerability in short-term, placebo-controlled trials.

Aripiprazole is a novel antipsychotic with a unique mechanism of action. Presented here is a pooled analysis of safety and tolerability data from all completed short-term, placebo-controlled trials in schizophrenia from the aripiprazole clinical development program. Data were analyzed from five 4- to 6-week double-blind multicenter studies of patients hospitalized with acute relapse of schizophrenia or schizoaffective disorder randomized to aripiprazole (n=932), placebo (n=416), or haloperidol (n=201). Daily aripiprazole doses ranged from 2 to 30 mg. Safety assessments included adverse event (AE) reports, EPS scales, ECGs, weight, and prolactin, glucose and cholesterol levels. Aripiprazole was well tolerated, with similar AE incidence rates to placebo, and lower rates than haloperidol for akathisia, extrapyramidal syndrome and somnolence. Objective EPS assessments demonstrated no significant differences between aripiprazole and placebo on Simpson-Angus Scale (SAS) scores, no dose-dependent effects on Barnes Akathisia scores, and significant reductions in Abnormal Involuntary Movement Scale (AIMS) scores from baseline vs. placebo (p</=0.01). Haloperidol showed increased SAS and Barnes Akathisia scores over placebo (p</=0.01). There was minimal mean weight change with aripiprazole (+0.71 kg) and haloperidol (+0.56 kg), and a lack of QT(c) prolongation. Serum prolactin increased with haloperidol, but not aripiprazole. In conclusion, aripiprazole shows a favorable safety and tolerability profile with low potential for EPS, weight gain, prolactin elevation, QT(c) prolongation, and sedation. Aripiprazole's safety profile may offer benefits in schizophrenia treatment.

Acute Disease↗

Aripiprazole, a novel atypical antipsychotic drug with a unique and robust pharmacology.

Atypical antipsychotic drugs have revolutionized the treatment of schizophrenia and related disorders. The current clinically approved atypical antipsychotic drugs are characterized by having relatively low affinities for D(2)-dopamine receptors and relatively high affinities for 5-HT(2A) serotonin receptors (5-HT, 5-hydroxytryptamine (serotonin)). Aripiprazole (OPC-14597) is a novel atypical antipsychotic drug that is reported to be a high-affinity D(2)-dopamine receptor partial agonist. We now provide a comprehensive pharmacological profile of aripiprazole at a large number of cloned G protein-coupled receptors, transporters, and ion channels. These data reveal a number of interesting and potentially important molecular targets for which aripiprazole has affinity. Aripiprazole has highest affinity for h5-HT(2B)-, hD(2L)-, and hD(3)-dopamine receptors, but also has significant affinity (5-30 nM) for several other 5-HT receptors (5-HT(1A), 5-HT(2A), 5-HT(7)), as well as alpha(1A)-adrenergic and hH(1)-histamine receptors. Aripiprazole has less affinity (30-200 nM) for other G protein-coupled receptors, including the 5-HT(1D), 5-HT(2C), alpha(1B)-, alpha(2A)-, alpha(2B)-, alpha(2C)-, beta(1)-, and beta(2)-adrenergic, and H(3)-histamine receptors. Functionally, aripiprazole is an inverse agonist at 5-HT(2B) receptors and displays partial agonist actions at 5-HT(2A), 5-HT(2C), D(3), and D(4) receptors. Interestingly, we also discovered that the functional actions of aripiprazole at cloned human D(2)-dopamine receptors are cell-type selective, and that a range of actions (eg agonism, partial agonism, antagonism) at cloned D(2)-dopamine receptors are possible depending upon the cell type and function examined. This mixture of functional actions at D(2)-dopamine receptors is consistent with the hypothesis proposed by Lawler et al (1999) that aripiprazole has "functionally selective" actions. Taken together, our results support the hypothesis that the unique actions of aripiprazole in humans are likely a combination of "functionally selective" activation of D(2) (and possibly D(3))-dopamine receptors, coupled with important interactions with selected other biogenic amine receptors--particularly 5-HT receptor subtypes (5-HT(1A), 5-HT(2A)).

Antipsychotic Agents↗

Efficacy and safety of aripiprazole and haloperidol versus placebo in patients with schizophrenia and schizoaffective disorder.

BACKGROUND: Aripiprazole is an investigational agent for treating schizophrenia that has a novel pharmacologic profile. The present study investigated the efficacy, safety, and tolerability of aripiprazole and haloperidol compared with placebo. METHOD: A 4-week, double-blind, randomized study, conducted at 36 U.S. centers between July 1997 and June 1998, compared aripiprazole (15 mg/day, 30 mg/day) to placebo, with haloperidol (10 mg/day) as an active control. Fixed doses of each agent were administered from day 1 throughout the study. A total of 414 patients with a primary DSM-IV diagnosis of schizophrenia or schizoaffective disorder were randomized. Efficacy measures included the Positive and Negative Syndrome Scale (PANSS) total, PANSS positive, PANSS negative, PANSS-derived Brief Psychiatric Rating Scale (BPRS) core, Clinical Global Impressions (CGI)-Severity of Illness, and mean CGI-Improvement scores. Safety and tolerability evaluations included extrapyramidal symptoms (EPS), weight gain, serum prolactin level, and QTc interval. RESULTS: Both doses of aripiprazole and haloperidol, 10 mg, produced statistically significant (p < or = .05) improvements from baseline in PANSS total, PANSS positive, PANSS-derived BPRS core, and CGI-Severity scores and significantly lower CGI-Improvement scores at endpoint, compared with placebo. Aripiprazole, 15 mg, and haloperidol, 10 mg, significantly improved PANSS negative score compared with placebo. Both aripiprazole doses and haloperidol separated from placebo for PANSS total scores at week 2. Unlike haloperidol, aripiprazole was not associated with significant EPS or prolactin elevation at endpoint compared with placebo. There were no statistically significant differences in mean changes in body weight across the treatment groups versus placebo, and no patients receiving aripiprazole experienced clinically significant increases in QTc interval. CONCLUSION: Aripiprazole, effective against positive and negative symptoms, is a safe and well-tolerated potential treatment for schizophrenia and schizoaffective disorder.

Acute Disease↗

Switching patients to aripiprazole from other antipsychotic agents: a multicenter randomized study.

RATIONALE: Switching patients from one antipsychotic to another can lead to tolerability problems or transient symptom exacerbations. It is important to compare switching strategies to determine which methods produce the best possible patient outcomes. OBJECTIVE: To investigate the efficacy, safety and tolerability of three dosing strategies for switching chronic, stable patients with schizophrenia from current oral antipsychotic monotherapy to once-daily oral aripiprazole monotherapy. METHOD: Patients in this 8-week, open-label, outpatient study were randomized to: 1). immediate initiation of 30 mg/day aripiprazole with simultaneous immediate discontinuation of current antipsychotic; 2). immediate initiation of 30 mg/day aripiprazole while tapering off current antipsychotic over 2 weeks; or 3). up-titrating aripiprazole to 30 mg/day over 2 weeks, while simultaneously tapering off current antipsychotic. Efficacy assessments included PANSS, CGI-S, and CGI-I scores. Safety assessments included: adverse events (AEs) recording, evaluation of extrapyramidal symptoms (EPS), vital signs, ECG, and clinical laboratory tests. RESULTS: Efficacy with aripiprazole was maintained during the study with numerical improvements compared with baseline in all three groups. The overall incidence of AEs was broadly comparable across all groups, and AEs were generally mild to moderate in severity and time-limited. Discontinuations due to AEs were comparable across the groups. No deterioration in EPS occurred in any group. The reduction in body weight and plasma prolactin levels following switch to aripiprazole were comparable across the three groups. CONCLUSION: Any of the three strategies evaluated can be used safely for switching patients to aripiprazole from antipsychotic monotherapy. Furthermore, patients' symptoms may continue to improve after switching to aripiprazole.

Adult↗

A placebo-controlled, double-blind study of the efficacy and safety of aripiprazole in patients with acute bipolar mania.

OBJECTIVE: The authors compared the efficacy and safety of aripiprazole, a novel antipsychotic, to placebo for treatment of patients in an acute manic or mixed episode of bipolar disorder. METHOD: This 3-week, multicenter, double-blind study randomly assigned 262 bipolar disorder patients in an acute manic or mixed episode to aripiprazole, 30 mg/day (reduced to 15 mg/day if needed for tolerability), or placebo. Patients remained hospitalized for at least 2 of the weeks. The primary efficacy measure was mean change from baseline in total score on the Young Mania Rating Scale; response was defined as a decrease in score of > or =50%. RESULTS: Aripiprazole produced statistically significant mean improvements in total score on the Young Mania Rating Scale compared with placebo (-8.2 versus -3.4, respectively) and produced a significantly higher response rate (40% versus 19%). For key efficacy variables (response per Young Mania Rating Scale; Clinical Global Impression-Bipolar Version scores for severity of illness [mania] and change from preceding phase [mania]), aripiprazole separated from placebo by day 4. The completion rate was significantly higher with aripiprazole than with placebo (42% versus 21%). Discontinuations due to adverse events did not differ significantly between the aripiprazole and placebo groups. There were no significant changes in body weight versus placebo, and aripiprazole was not associated with elevated serum prolactin or QTc prolongation. CONCLUSIONS: Aripiprazole had significantly greater efficacy than placebo for the treatment of bipolar disorder patients in acute manic or mixed episodes and was safe and well tolerated in this randomized controlled trial.

Acute Disease↗

In vivo canine model comparison of cardiohemodynamic and electrophysiological effects of a new antipsychotic drug aripiprazole (OPC-14597) to haloperidol.

The cardiovascular effects of aripiprazole were assessed in comparison with those of haloperidol using a halothane-anesthetized canine model with monophasic action potential monitoring. Aripiprazole (n = 6) or haloperidol (n = 6) was infused over 10 min at escalating doses of 0.03, 0.3, and 3.0 mg/kg with intervals of 20 min between doses. Clinically relevant plasma concentrations were obtained after 0.03-0.3 mg/kg of aripiprazole as well as haloperidol. After 0.03-0.3 mg/kg of aripiprazole, positive chronotropic, inotropic, and dromotropic effects, shortening of the ventricular effective refractory period (ERP) and repolarization phase, and decrease of total peripheral resistance were observed in a dose-related manner. However, in the presence of a beta-blocking dose of esmolol (0.1 mg/kg/min), these changes were not induced. After 3.0 mg/kg of aripiprazole administration, cardiac effects induced by the lower doses were attenuated or disappeared, while the negative chronotropic, dromotropic, and hypotensive actions and prolongation of ERP and repolarization phase were induced. After 0.03 mg/kg of haloperidol, no significant change was observed, except for the decrease of the peripheral resistance. After 0.3-3.0 mg/kg of haloperidol, negative chronotropic, inotropic, and hypotensive actions, intraventricular conduction delay, and prolongation of ventricular ERP and repolarization phase were observed in a dose-related manner accompanied by further decrease of the peripheral resistance. The inhibitory effects of aripiprazole on cardiovascular parameters in dogs were less potent than those of haloperidol at clinically relevant exposures, moreover, aripiprazole, unlike haloperidol, neither induced early afterdepolarization nor prolonged the ventricular electrical vulnerable period. Therefore, aripiprazole can be considered safer to use than haloperidol.

Animals↗

Inhibition by aripiprazole of dopaminergic inputs to striatal neurons from substantia nigra.

RATIONALE: Aripiprazole (OPC-14597) elicits both dopamine D(2) agonist and antagonist activities on dopaminergic neurons of the ventral tegmental area and nucleus accumbens neurons, respectively. However, the electrophysiological action of this drug on the striatal neurons is not clear. OBJECTIVE: Therefore, the present electrophysiological study was performed to determine if aripiprazole modified the striatal neurons as a D(2) receptor agonist or antagonist. METHODS: Spikes elicited by stimulation of pars compacta of the substantia nigra (SN) were extracellularly recorded from the striatal neurons with a glass microelectrode attached along a seven- barreled micropipette. Each barrel was filled with aripiprazole, quinpirole (D(2) receptor agonist), domperidone (D(2) receptor antagonist), glutamate or 2 M NaCl. The drugs were microiontophoretically applied on the neurons being recorded. RESULTS: The effects of aripiprazole on SN stimulation-induced spikes of striatal neurons that were inhibited by domperidone were examined. Microiontophoretic application of aripiprazole inhibited spikes elicited by SN stimulation in all 18 neurons tested in a dose-dependent manner. In addition, quinpirole-induced firing was inhibited by aripiprazole in all ten neurons tested. However, glutamate-induced spontaneous firing was not affected by aripiprazole in any of the ten neurons tested. CONCLUSIONS: These findings suggest that aripiprazole acts as a dopamine D(2) receptor antagonist on striatal neurons receiving excitatory inputs from the SN.

Animals↗

Aripiprazole.

Aripiprazole is a quinolinone derivative and the first of a new class of atypical antipsychotics. The drug has partial agonist activity at dopamine D(2) and serotonin 5-HT(1A) receptors, and is also an antagonist at 5-HT(2A) receptors. In patients with acute relapse of schizophrenia or schizoaffective disorder, aripiprazole 15 to 30 mg/day was at least as effective as haloperidol 10 mg/day and had similar efficacy to risperidone 6 mg/day in well designed, 4-week, placebo-controlled trials. Negative symptoms improved earlier in the aripiprazole than the risperidone group. Efficacy of aripiprazole was observed at week 1 in several trials and was sustained throughout the study periods. Aripiprazole was superior to placebo in a 26-week trial in patients with stable, chronic schizophrenia. In a 52-week trial involving patients with acute relapsing disease, aripiprazole was similar to haloperidol as assessed by time to failure to maintain response and was superior in ameliorating negative and depressive symptoms. The incidence of extrapyramidal symptoms during aripiprazole therapy was similar to that with risperidone and placebo but lower than with haloperidol. Compared with placebo, the proportion of patients with increased plasma prolactin levels and QTc prolongation was similar in patients treated with aripiprazole 15 to 30 mg/day but was significantly increased with haloperidol and risperidone.

Animals↗

Aripiprazole (Otsuka Pharmaceutical Co).

Otsuka Pharmaceuticals in collaboration with Bristol-Myers Squibb is developing aripiprazole, a dual dopamine autoreceptor agonist and postsynaptic D2 receptor antagonist, for the potential treatment of psychoses including schizophrenia [281327], [340364]. A regulatory filing for schizophrenia in the US was submitted at the end of 2001 [340364]. The compound entered phase III trials in Japan in 1995 [192966]. Although presynaptic dopamine autoreceptor agonists may be efficacious in the treatment of schizophrenia, they may also potentially increase the risk for exacerbation of psychosis through stimulation of postsynaptic dopaminergic receptors [245791], [350478], [350479]. However, earlier neuropharmacology studies have shown that aripiprazole can act as a presynaptic D2 agonist while displaying an antagonistic effect at the postsynaptic D2 receptors [281327], [337126], [350479], [424587], [424588]. In animal models, aripiprazole inhibits the apomorphine-induced stereotypy, without causing catalepsy [281327], [337126]. Moreover, in contrast to classical antipsychotics that produce disabling movement disorders, aripiprazole does not cause an upregulation of D2 receptors or an increase in expression of the c-fos mRNA in the striatum, in agreement with the low risk for extrapyramidal side effects (EPS) during aripiprazole treatment [245781], [262096], [350481], [350483]. Collectively, aripiprazole is an important atypical antipsychotic candidate with a favorable safety profile. Moreover, the mechanism of action of aripiprazole differentiates it from both typical and atypical antipsychotics and hence, may provide important leads for pharmacotherapy of schizophrenia and other psychotic disorders. In January 2000, Lehman Brothers predicted peak sales of aripiprazole could reach US $500 million [357788]. In February 2001, Credit Suisse First Boston predicted sales of US $403 million in 2005 [399484].

Animals↗

Aripiprazole, a novel antipsychotic drug, inhibits quinpirole-evoked GTPase activity but does not up-regulate dopamine D2 receptor following repeated treatment in the rat striatum.

Aripiprazole, a quinolinone derivative, is a new dopaminergic agent which has been recently developed and demonstrated to be clinically useful as an antipsychotic drug with reduced extrapyramidal motor side effects. Here, we found that aripiprazole competed [3H]spiperone binding with a 100-fold higher affinity than [3H]SCH23390 binding, and inhibited the quinpirole-induced facilitation of high-affinity GTPase activity in rat striatal membranes. The effects of chronic administration of aripiprazole and haloperidol on dopamine D2 receptor binding and mRNA level in rat striata were examined by a [3H]spiperone binding assay and a ribonuclease protection assay. Haloperidol induced a significant rise in Bmax of [3H]spiperone binding at 1 mg/kg and in the level of dopamine D2L receptor mRNA at 4 mg/kg. A high dose of aripiprazole (100 mg/kg) only tended to increase the Bmax of [3H]spiperone binding non-significantly, and had no effect on the level of dopamine D2L receptor mRNA. These results indicated that aripiprazole had an antagonistic activity to dopamine D2 receptors with a high affinity, but that the potency of aripiprazole to up-regulate dopamine D2 receptors in the striatum was much smaller than that of haloperidol. This small up-regulation may be related to the ability to aripiprazole to act without side effects including tardive dyskinesia.

Animals↗

Diminished catalepsy and dopamine metabolism distinguish aripiprazole from haloperidol or risperidone.

Catalepsy and changes in striatal and limbic dopamine metabolism were investigated in mice after oral administration of aripiprazole, haloperidol, and risperidone. Catalepsy duration decreased with chronic (21 day) aripiprazole compared with acute (single dose) treatment across a wide dose range, whereas catalepsy duration persisted with chronic haloperidol treatment. At the time of maximal catalepsy, acute aripiprazole did not alter neostriatal dopamine metabolite/dopamine ratios or homovanillic acid (HVA) levels, and produced small increases in dihydroxyphenylacetic acid (DOPAC). Effects were similar in the olfactory tubercle. Dopamine metabolism was essentially unchanged in both regions after chronic aripiprazole. Acute treatments with haloperidol or risperidone elevated DOPAC, HVA, and metabolite/dopamine ratios in both brain areas and these remained elevated with chronic treatment. The subtle effects of aripiprazole on striatal and limbic dopamine metabolism, and the decrease in catalepsy with chronic administration, illustrate fundamental differences in dopamine neurochemical actions and behavioral sequelae of aripiprazole compared to haloperidol or risperidone.

Administration, Oral↗

Aripiprazole: a new atypical antipsychotic drug.

OBJECTIVE: To review the pharmacology, pharmacokinetics, clinical efficacy, and safety profile of aripiprazole for the treatment of schizophrenia. DATA SOURCES: Information was selected from MEDLINE (1995-August 2002). Abstracts, scientific posters, and presentations were also used. STUDY SELECTION/DATA EXTRACTION: All published information regarding the pharmacokinetic, pharmacodynamic, and clinical characteristics of aripiprazole was considered. Studies providing a comprehensive description of aripiprazole were selected. DATA SYNTHESIS: Aripiprazole is a dopamine partial agonist and a serotonin-2A antagonist; it is dosed 10-30 mg/d, with no initial titration necessary. Short-term clinical trials demonstrated efficacy in acute exacerbations, and long-term studies showed that aripiprazole can maintain remission of schizophrenia. Most adverse events were mild. The incidence of extrapyramidal symptoms was low, with akathisia being the most common. CONCLUSIONS: Aripiprazole currently demonstrates comparable efficacy and safety for use in schizophrenia.

Antipsychotic Agents↗

Dopamine D2 and D3 receptor occupancy in normal humans treated with the antipsychotic drug aripiprazole (OPC 14597): a study using positron emission tomography and [11C]raclopride.

Aripiprazole (OPC 14597) is an antipsychotic drug that has high affinity for dopamine D2 and D3 receptors and the dopamine autoreceptor. It is being developed for treatment of patients with schizophrenia. The purpose of this study was to determine whether a dose response following graduated doses of aripiprazole could be quantified and correlated with its occupancy of the D2 and D3 dopamine receptors in the brain of living humans. Dopamine D2 and D3 receptor occupancy in fifteen normal male human brains was measured using positron emission tomography (PET) with [11C]raclopride. PET studies were performed before and after two weeks of administration of aripiprazole. The dopamine D2 receptor occupancy was quantified with two kinetic modeling methods without using a blood input function. Administration of aripiprazole for 14 days resulted in a dose-dependent receptor occupancy between 40 - 95% after the administration of 0.5mg, 1 mg, 2 mg, 10 mg, and 30 mg per day. These results suggest that an adequate occupancy can be obtained, and this may be useful to predict an appropriate therapeutic dose for an individual patient. Interestingly, even at striatal D2 receptor occupancy values above 90%, which occurred with the higher doses, extrapyramidal side effects (EPS) were not observed. This underlines aripiprazole's unique mechanism of action as a partial dopamine receptor agonist, which might become a novel principle in the treatment of schizophrenia.

Administration, Oral↗

Aripiprazole: a partial dopamine D2 receptor agonist antipsychotic.

This paper reviews the clinical pharmacology, efficacy and safety of the novel antipsychotic drug aripiprazole. All published citations regarding aripiprazole were reviewed using a Medline((R)) search (completed for citations through mid-year, 2002). In addition, abstracts from recent scientific meetings presenting data not yet published (nor peer-reviewed) were reviewed. Aripiprazole has a unique mechanism of action as a dopamine D2 partial agonist, serotonin 5-HT(1A) partial agonist and serotonin 5-HT(2A) antagonist. Like other new antipsychotics, aripiprazole has the profile of an atypical agent, with efficacy in the treatment of positive and negative symptoms of psychosis as well as mood symptoms, a low rate of neurological side effects and no significant adverse effect on serum prolactin concentrations. In addition, aripiprazole was not associated with significant weight gain or QTc prolongation in both acute and long-term treatment trials.

Animals↗

Aripiprazole: profile on efficacy and safety.

Aripiprazole (Abilitat, Bristol-Myers Squibb) is the most recent addition to the new class of atypical antipsychotic medications, following the release of clozapine, risperidone, olanzapine, quetiapine and ziprasidone. Aripiprazole exhibits typical antagonism at dopamine (D2) receptors in the mesolimbic pathway, as well as having unique partial agonist activity at D2 receptors in the mesocortical pathway. As exemplified by other atypical antipsychotics, it displays strong 5-HT(2a) receptor antagonism and is similar to ziprasidone in also having agonistic activity at the 5-HT(1a) receptor. Among the atypical antipsychotics, aripiprazole displays the lowest affinity for alpha(1)adrenergic (alpha(1)), histamine (H1) and muscarinic (M1) receptors. This combination of effects may be responsible for its efficacy in positive and negative symptoms of schizophrenia and in bipolar disorder. Similarly, this profile may be the reason for the low rates of reported side effects observed. This includes general adverse events, a low incidence of reported weight gain and a low liability for inducing movement disorders. Other early data suggest that aripiprazole may induce reductions in plasma prolactin, as well as in plasma glucose and lipid profiles. Finally, results also support the proposition that aripiprazole may lead to reductions in corrected QT interval and have minimal drug interactions.

Antipsychotic Agents↗

Aripiprazole: a review of its pharmacology and clinical use.

Atypical antipsychotics generally have a lower propensity for extrapyramidal side-effects (EPSE), hyperprolactinaemia and tardive dyskinesia than that associated with typical antipsychotics but may still produce troublesome side-effects, such as weight gain, cardiac rhythm changes and impaired glucose tolerance. Aripiprazole is a new atypical antipsychotic with a unique receptor binding profile that combines partial agonist activity at D2 and 5HT1A receptors with potent antagonism at 5HT2A receptors. Clinical studies in acute schizophrenic relapse, chronic schizophrenia and acute mania show it is robustly more effective than placebo. Once-daily aripiprazole 15-30 mg is as effective as haloperidol 10 mg/day and risperidone 6 mg/day in short-term treatment of schizophrenia and more effective than haloperidol 7-10 mg/day in maintenance of response in chronic schizophrenia. Aripiprazole appears to be well tolerated, with most studies suggesting a frequency of adverse effects similar to placebo. Aripiprazole seems not to cause significant EPSE, hyperprolactinaemia, excessive weight gain or cardiac rhythm disturbance. Limited data suggest that aripiprazole is not associated with impaired glucose tolerance.

Antipsychotic Agents↗