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

Update on the Pharmacological Treatment of Tics with Dopamine-Modulating Agents

More than 40 years of research and clinical practice have proven the effectiveness of dopamine receptor antagonists in the pharmacological treatment of tics. A blockade of the striatal dopamine-D2 receptors is mainly responsible for their tic-reducing effect. A broad spectrum of dopamine-modulating agents, such as typical and atypical antipsychotics, but also dopamine receptor agonists are used with an immanent discord between experts about which of them should be considered as first choice. The present Review outlines the state of the art on pharmacological treatment of tics with dopamine-modulating agents by giving an systematic overview of studies on their effectiveness and a critical discussion of their specific adverse effects. It is considered as an update of a previous review of our research group published in 2013. The Review closes with a description of the current resulting treatment recommendations including the results of a first published revised survey on European expert's prescription preferences. Based on the enormously growing evidence on its effectiveness and safety, aripiprazole currently seems to be the most promising agent in the pharmacological treatment of tics. Furthermore, benzamides (especially tiapride), which are commonly used in Europe, have proven their excellent effectiveness-tolerability profile over decades in clinical practice and are therefore also highly recommended for the treatment of tics. Nevertheless, pharmacological treatment of tics remains an indiviual choice depending on each patient's own specific needs.

Aripiprazole

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Aripiprazole: pharmacology, efficacy, safety and tolerability

Aripiprazole is a recently released antipsychotic medication which differs from other atypical antipsychotic agents by its partial agonist activity at postsynaptic D2 receptors. It is administered orally and is distinguished by a long elimination phase half-life relative to other antipsychotic medications. Randomized studies have demonstrated the efficacy of aripiprazole relative to placebo in the treatment of acute relapse of schizophrenia and schizoaffective disorder, maintenance treatment of schizophrenia, and treatment of acute bipolar mania. Aripiprazole is generally well tolerated relative to other antipsychotic medications, although commonly reported side effects include worsening extrapyramidal symptoms and motoric activation similar to akathisia. Further studies and postmarketing data will be helpful in providing additional information about the comparative safety, efficacy and tolerability of aripiprazole.

Aripiprazole: a review of its use in the management of schizophrenia in adults

Oral aripiprazole (Abilify®) is an atypical antipsychotic agent that is approved worldwide for use in adult patients with schizophrenia. It is a quinolinone derivative that has a unique receptor binding profile as it exhibits both partial agonist activity at dopamine D(2) receptors and serotonin 5-HT(1A) receptors and antagonist activity at 5-HT(2A) receptors. In several well designed, randomized, clinical trials of 4-6 weeks duration, aripiprazole provided symptomatic control for patients with acute, relapsing schizophrenia or schizoaffective disorder. Furthermore, following 26 weeks' treatment, the time to relapse was significantly longer for patients with chronic, stabilized schizophrenia receiving aripiprazole compared with those receiving placebo. Using a variety of efficacy outcomes, aripiprazole showed a mixed response when evaluated against other antipsychotic agents in randomized clinical trials. Longer-term data showed that improvements in remission rates and response rates favoured aripiprazole over haloperidol, although, the time to failure to maintain a response was not significantly different between the treatment arms. On the other hand, improvements in positive and negative symptom scores mostly favoured olanzapine over aripiprazole, although, the time to all-cause treatment discontinuation was not significantly different between the two treatments. Several open-label, switching trials showed that aripiprazole provided continued control of symptoms in patients with schizophrenia or schizoaffective disorder. Using a variety of efficacy outcomes or quality-of-life scores, longer-term treatment generally favoured patients switched to receive aripiprazole compared with standard-of-care oral antipsychotics. Aripiprazole was generally well tolerated in patients with schizophrenia. In particular, its use seems to be associated with a lower incidence of extrapyramidal symptoms than haloperidol and fewer weight-gain issues than olanzapine. Aripiprazole also showed a favourable cardiovascular tolerability profile and its use was associated with a reduced risk of metabolic syndrome than placebo or olanzapine. As a consequence, aripiprazole may provide a more cost-effective treatment option compared with other atypical antipsychotics. In conclusion, oral aripiprazole provides an effective and well tolerated treatment alternative for the acute and long-term management of patients with schizophrenia.

Repeated aripiprazole administration attenuates cocaine seeking in a rat model of relapse

RATIONALE

Aripiprazole (Abilify) is an atypical antipsychotic drug characterized by partial agonist activity at dopamine (DA) D(2)/D(3) receptors and a low side-effect profile. While we previously demonstrated that acute aripiprazole blocked the reinstatement of cocaine seeking in an animal model of relapse, clinical treatment of relapse prevention necessitates testing the effects of aripiprazole following prolonged abstinence, as well as after repeated administration during withdrawal from cocaine.

OBJECTIVES

We assessed the effects of repeated aripiprazole treatment on cocaine seeking after abstinence and during conditioned cue-induced and cocaine-primed reinstatement in rats.

MATERIALS AND METHODS

Rats self-administered intravenous cocaine paired with a light + tone stimulus for 10-14 days, followed by 2 weeks of abstinence. Following post-abstinence relapse testing, lever responding was allowed to extinguish, with subsequent reinstatement testing occurring either in the presence of the conditioned stimulus, or after a cocaine-priming injection (10 mg/kg, intraperitoneal (IP)). Following 3 or 7 days of pretreatment, rats received an injection of aripiprazole (0.25, 0.5, and 1.0 mg/kg, IP) or vehicle prior to post-abstinence relapse and reinstatement testing.

RESULTS

Vehicle-pretreated animals showed robust cocaine seeking during relapse and reinstatement testing, an effect that was significantly attenuated by aripiprazole pretreatment, although no lasting effects were found in the absence of acute injection.

DISCUSSION

These findings support the possibility that repeated aripiprazole may be an effective therapeutic agent for the prevention of relapse in abstinent cocaine users. Based on its antipsychotic profile, aripiprazole may be particularly useful for individuals diagnosed with comorbid psychoses, such as schizophrenia or bipolar disorder.

Electrophysiological studies in the rat brain on the basis for aripiprazole augmentation of antidepressants in major depressive disorder

RATIONALE

Aripiprazole (ARI) is an atypical antipsychotic approved by the Food and Drug Administration for use in major depressive disorder as an adjunct to antidepressants. However, the precise mechanisms responsible for the effectiveness of ARI augmentation are not fully understood.

OBJECTIVES

The current study was aimed at examining the effects of ARI administration alone and in combination with the selective serotonin reuptake inhibitors (SSRI) escitalopram (ESC) on the firing of serotonin (5-HT), norepinephrine (NE), and dopamine (DA) neurons.

METHODS

Electrophysiological experiments were carried out in anesthetized Sprague-Dawley rats. ESC was delivered via subcutaneously implanted osmotic minipumps at a dose of 10 mg/kg/day. ARI was subcutaneously injected daily at a dose of 2 mg/kg/day. Both drugs were administered for 2 and 14 days alone and in combination. Control rats received physiological saline in analogous regimens.

RESULTS

Two-day ESC administration resulted in a significant decrease in the firing rate of 5-HT, NE, and DA neurons. Following 14 days of ESC administration, 5-HT firing returned to the baseline. The firing rate of NE and DA neurons remained significantly decreased. ARI administered for 2 or 14 days significantly increased the firing rate of 5-HT neurons by 36% and 48%, respectively, but not those of DA and NE neurons. Desensitization of somatodendritic 5-HT autoreceptors was observed after 2 days of ARI administration. The combination of the two drugs reversed the inhibitory action of ESC on the firing rate of 5-HT, NE, and DA neurons.

CONCLUSION

The present study showed that addition of ARI to an SSRI regimen reverses the inhibitory action of the SSRI on monoaminergic neuronal firing.

Use of atypical antipsychotics for treatment-resistant major depressive disorder

Despite the progressive increase in the number of pharmacologic agents with potential antidepressant activity, many patients suffering from major depressive disorder (MDD) continue to be symptomatic. Clearly, an urgent need exists to develop safer, better tolerated, and more effective treatments for MDD. Use of atypical antipsychotic agents as adjunctive treatment for treatment-resistant MDD (TRD) represents one such effort toward novel pharmacotherapy development. Atypical antipsychotic agents have been hypothesized to be beneficial in treating mood disorders, including TRD, as a result of their complex mechanisms of action. After an initial series of positive case reports, series, and small clinical trials, subsequent larger-scale projects have yielded conflicting results. However, more recently, larger-scale clinical trials have supported the effectiveness of at least some of these medications. This review summarizes the existing data regarding the effectiveness of these medications in treating TRD, including biochemical rationale and clinical data.

Novel antipsychotics in schizophrenia

Several atypical antipsychotics have become available for the treatment of schizophrenia that are at least as effective as conventional treatment and with fewer extrapyramidal side effects. Their presumed mechanisms of therapeutic action vary and are no longer limited to dopamine D2 receptor antagonism. Numerous novel drugs are in development, with a variety of receptor affinities and other supposed therapeutic effects. This article will review current developments in drug discovery alongside contemporary evidence for potential substrates and mechanisms of antipsychotic action. Despite many promising developments there is no ideal antipsychotic to date. Progress in drug treatment for schizophrenia is confronted by several areas of difficulty which, barring serendipity, must be resolved before real advances can be anticipated.

Aripiprazole: a review of its use in schizophrenia and schizoaffective disorder

Aripiprazole, a quinolinone derivative, is an atypical antipsychotic drug indicated for the treatment of adult patients with schizophrenia. Aripiprazole 10 or 15 mg once daily is effective and well tolerated in patients with schizophrenia or schizoaffective disorder. Although aripiprazole has only been directly compared with haloperidol and olanzapine in treatment-responsive patients to date, current data generally indicate that aripiprazole has a beneficial profile in terms of a low potential for bodyweight gain. Dosage titration is not necessary and the drug is effective in the first few weeks of treatment. Head-to-head comparative trials with atypical antipsychotic agents are required, as are long-term (> or =1 year) studies, to fully define the position of aripiprazole in relation to other antipsychotic drugs. Aripiprazole is a valuable new therapeutic option in the management of patients with schizophrenia. PHARMACOLOGICAL PROPERTIES: Aripiprazole is a quinolinone derivative with a high affinity for dopamine D2 and D3 receptors, and serotonin 5-HT1A, 5-HT2A and 5-HT2B receptors. The mechanism of action of aripiprazole is not yet known, but evidence suggests that its efficacy in the treatment of the positive and negative symptoms of schizophrenia and its lower propensity for extrapyramidal symptoms (EPS) may be attributable to aripiprazole's partial agonist activity at dopamine D2 receptors. At serotonin 5-HT1A receptors, in vitro studies have shown that aripiprazole acts as a partial agonist whereas at serotonin 5-HT2A receptors aripiprazole is an antagonist. The main active metabolite, dehydro-aripiprazole, has affinity for dopamine D2 receptors and thus has some pharmacological activity similar to that of the parent compound. Aripiprazole is rapidly absorbed after oral administration. The mean time to peak plasma concentration is 3 hours following multiple-dose administration of aripiprazole 10 or 15 mg and the absolute oral bioavailability of the drug is 87%. Steady-state plasma drug concentrations are achieved by 14 days; however, the drug appears to accumulate over this period, since mean peak plasma concentration and mean area under the plasma concentration-time curve values of aripiprazole 10 or 15 mg/day are 4-fold greater on day 14 than on day 1. This accumulation may be expected, since the mean elimination half-life of a single dose of aripiprazole is about 75 hours. Aripiprazole has extensive extravascular distribution and more than 99% of aripiprazole and dehydro-aripiprazole (the main active metabolite of aripiprazole) is bound to plasma protein. Elimination of the drug is primarily hepatic; the cytochrome P450 (CYP) 3A4 and CYP2D6 enzyme systems transform aripiprazole to dehydro-aripiprazole, with the latter enzyme system subject to genetic polymorphism. Thus, dosage adjustment of aripiprazole is necessary when it is coadministered with CYP3A4 and CYP2D6 inhibitors (since aripiprazole concentration is increased) and with inducers of CYP3A4 (since aripiprazole concentration is decreased). THERAPEUTIC EFFICACY: The efficacy of aripiprazole has been demonstrated in patients with schizophrenia or schizoaffective disorder. In general, significant reductions from baseline in mean Positive and Negative Syndrome Scale total, positive and negative symptom scores, and Clinical Global Impression Severity of Illness scores were observed in patients with acute relapse of chronic schizophrenia or schizoaffective disorder receiving recommended (10 or 15 mg/day) or higher-than-recommended (20 or 30 mg/day) dosages of aripiprazole versus those receiving placebo in three well controlled, short-term trials. No additional therapeutic benefit was observed at the higher-than-recommended dosages. The drug is effective as early as the first or second week of treatment. The efficacy of aripiprazole was maintained for up to 52 weeks. The drug was significantly more effective than placebo in preventing relapse in patients with stable chronic schizophrenia in a 26-week, randomised trial. In a 52-week trial in patients with acute relapse of schizophrenia, the percentage of responders maintaining a response at study end was 77% of aripiprazole versus 73% of haloperidol recipients. Aripiprazole may improve cognitive function. In a nonblind, 26-week trial, patients with chronic schizophrenia receiving aripiprazole 30 mg/day experienced similar (general cognitive function) or better (verbal learning) changes from baseline in the neurocognitive parameters evaluated compared with recipients of olanzapine 10-15 mg/day.

TOLERABILITY

Aripiprazole 10-30 mg/day was generally well tolerated. The tolerability profile of aripiprazole was broadly similar to that observed with placebo in a meta-analysis of short-term trials in patients with acute relapse of schizophrenia or schizoaffective disorder and in a 26-week trial in patients with chronic stable schizophrenia. The most frequent treatment-emergent adverse events included insomnia and anxiety, and additionally, headache and agitation (in short-term trials) or akathisia and psychosis (in a 52-week trial). In general, the drug was associated with a placebo-level incidence of EPS and EPS-related adverse events. Significantly fewer aripiprazole recipients experienced EPS-related adverse events than haloperidol recipients in a 52-week trial. Changes in severity of EPS were minimal and usually no different from those observed with placebo. Moreover, there was less severe EPS in the aripiprazole group than the haloperidol group in a long-term trial. Treatment-emergent tardive dyskinesia was reported in only 0.2% of patients receiving aripiprazole (short-term trials), an incidence similar to that seen in placebo recipients (0.2%). Aripiprazole has a low propensity to cause clinically significant bodyweight gain, hyperprolactinaemia or corrected QT interval prolongation in patients with schizophrenia or schizoaffective disorder. In addition, there were no clinically relevant differences in mean changes from baseline in measures of diabetes and dyslipidaemia between the aripiprazole or placebo groups in a 26-week, placebo-controlled trial.

Aripiprazole: A comprehensive review of its pharmacology, clinical efficacy, and tolerability

BACKGROUND

Recently approved for the treatment of schizophrenia, aripiprazole represents the sixth second-generation antipsychotic (SGA) introduced to the US market. Aripiprazole is considered a partial dopaminergic agonist, acting on both postsynaptic dopamine(2) receptors and presynaptic autoreceptors, in addition to displaying partial agonism at serotonin(1A) receptors and antagonism at serotonin(2A) receptors.

OBJECTIVE

The aim of this study was to comprehensively review all available literature regarding the mechanism of action, pharmacokinetics, clinical efficacy, and adverse effects of aripiprazole.

METHODS

Relevant data were collected using MEDLINE and International Pharmaceutical Abstracts searches with the terms aripiprazole and OPC-14597 and with no limitations on year. Abstracts and posters presented at national and international scientific meetings were also reviewed.

RESULTS

Aripiprazole exhibits linear pharmacokinetics and is administered once daily. In multiple clinical trials, aripiprazole was effective in significantly reducing symptomatology associated with schizophrenia-related disorders compared with placebo (P < 0.05). Dosages > or =15 mg/d more consistently produced significant reductions from baseline of Positive and Negative Syndrome Scale total scores (P < 0.05) and were more likely to elicit a response than smaller dosages. Effects observed were comparable to those seen with risperidone and haloperidol, which were also significantly more effective than placebo (P < or = 0.05). Aripiprazole exhibited a favorable safety and tolerability profile, with a low propensity to cause extrapyramidal symptoms, weight gain, cardiovascular abnormalities, hyperprolactinemia, hypercholesterolemia, or glucose dysregulation.

CONCLUSIONS

Aripiprazole represents a well-tolerated and effective addition to the antipsychotic armamentarium. However, definitive advantages associated with dopamine partial agonism have yet to be determined. Long-term, head-to-head comparisons with other SGAs are needed to establish the effects of chronic administration and the relative safety and efficacy of aripiprazole.

Focus on aripiprazole

This paper is an overview of recently published research concerning the neuroleptic drug aripiprazole. Aripiprazole is an antipsychotic drug with high affinity for D(2)- and D(3)-receptors and the dopamine autoreceptor. It also has serotonin 5-HT(1A)-receptor partial agonist and 5-HT(2A)-receptor antagonist properties. It is prescribed in the treatment of schizophrenia and is under the treatment of schizophrenia and schizoaffective investigation for treatment of bipolar disorder. The drug is given by mouth in an initial dose of 10 or 15 mg once daily. The dose may be adjusted at intervals of not less than 2 weeks up to a maximum of 30 mg daily. It appears to be useful in disorder and has a better side-effect profile than haloperidol.

Antipsychotic treatment in schizophrenia: atypical options and NICE guidance

Following the reintroduction of clozapine, several atypical antipsychotics have become available for the treatment of schizophrenia. These drugs are at least as effective as conventional treatment. Although each has an individual pattern of affinities, new work suggests that the hallmark of atypicality is fast dissociation at the dopamine-2 receptor. Numerous novel drugs are in development, but it is not clear how these conform to this theory of therapeutic effect. Atypical antipsychotics cause less extrapyramidal side effects than conventional treatment, but other effects such as hyperprolactinaemia, weight gain, glucose dysregulation and prolonged QTc interval remain problematic for some. Current antipsychotic prescribing practice is far from ideal: the NICE guidance stresses that atypical treatments should be considered unless symptoms are well controlled and side effects are acceptable, or depot formulation is indicated. There is a welcome emphasis on drug treatment as part of an integrated package of care negotiated with patients and their carers.

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.

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.