Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aripiprazole is the first dopamine D(2) receptor partial agonist approved for use in schizophrenia and bipolar disorder. Other partial agonists have failed in various stages of development, either for reasons of poor tolerability or lack of efficacy. We conducted an in vitro comparative analysis between aripiprazole, bifeprunox, SDZ 208-912, OPC-4392 and ACR16 in attempt to correlate specific pharmacological properties with clinical outcome. In vitro pharmacological assessment included inhibition of forskolin-stimulated cAMP accumulation and the reversal of this inhibition produced by dopamine in clonal CHO cell lines expressing high and low densities of human dopamine D(2L) and D(2S) receptors. In cells expressing high receptor densities, all drugs except ACR16 predominantly behaved as agonists. However, in cells expressing low receptor densities, all drugs showed significantly lower maximal effects than dopamine. Aripiprazole's intrinsic activity was lower than that observed with bifeprunox and OPC-4392, and higher than that of SDZ 208-912. Aripiprazole's antagonist activity was greater than that of bifeprunox and OPC-4392, and less than that of SDZ 208-912. In conclusion, our data suggests that aripiprazole's unique intrinsic activity profile may account for its demonstrated clinical efficacy in the treatment of both positive and negative symptoms of schizophrenia, as well as its demonstrated low liability for parkinsonism and hyperprolactinemia. A higher degree of intrinsic activity, and lower relative antagonist activity, such as that observed with bifeprunox and OPC-4392 may translate into a clinically suboptimal improvement of positive symptoms. SDZ 208-912's intrinsic activity may be lower than the optimal level needed to minimize extrapyramidal symptoms.
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PMID:Differences in agonist/antagonist properties at human dopamine D(2) receptors between aripiprazole, bifeprunox and SDZ 208-912. 1769 41

Aripiprazole is a novel antipsychotic with a mechanism of action different from those of traditional first- and second-generation antipsychotics. We describe three patients with long histories of treatment for schizophrenia or schizoaffective disorder in whom conversion to aripiprazole was being attempted. After they started aripiprazole, their psychosis, agitation, anxiety, or aggression worsened. Although the cause of the increased agitation was unclear, it may have been related to long-term use of dopamine-blocking antipsychotics and resultant upregulation of postsynaptic dopamine receptors. The mechanism of partial dopamine agonism observed with aripiprazole may increase dopaminergic activity and worsen positive dopamine-associated symptoms, such as paranoia, agitation, and aggression. The treatment of schizophrenia is often a clinical challenge, particularly when patients have a long history of noncompliance and poor response. Clinicians face difficult decisions in finding an effective and well-tolerated regimen. These cases magnify some of the challenges and provide insight into the clinical implications of converting to therapies with different pharmacodynamic effects.
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PMID:Agitation associated with aripiprazole initiation. 1772 88

Alterations in muscarinic M1 receptor protein and mRNA expression have been revealed in post-mortem brains of schizophrenia patients. Most patients had been treated with antipsychotics, so medication effects cannot be excluded as a possible explanation for these results. With in situ hybridization, this study investigated M1 receptor mRNA expression in rats treated with the typical antipsychotic haloperidol (0.3 mg/kg/day) and the atypical antipsychotics olanzapine (1.5 mg/kg/day) and aripiprazole (2.25 mg/kg/day) for 1 or 12 weeks. Compared with the control group, haloperidol significantly increased (approximately 13-21%, P < 0.05) M1 mRNA expression in the CA1, CA2, and CA3 regions of the hippocampus after both 1 and 12 weeks of treatment, and it also increased (approximately 17%, P < 0.01) M1 mRNA expression in the substantia nigra compacta after 1 week of treatment. Olanzapine significantly increased (14-22%, P < 0.05) M1 mRNA expression in the hippocampus (CA1, CA2, and CA3) and substantia nigra compacta after 12 weeks of treatment, but not after 1 week. Aripiprazole significantly increased (17%, P < 0.01) M1 mRNA expression in the hippocampus (CA1) after both 1 and 12 week treatments and increased (12%, P < 0.05) M1 mRNA expression in the nucleus accumbens after 1 week of treatment. Despite their different affinities for muscarinic M1 receptors, all three antipsychotic medications induced a similar trend of change in M1 mRNA expression in selected brain regions. These data suggest that the decreased M1 receptor protein and mRNA expression observed in schizophrenia patients is unlikely to be a consequence of drug treatments and implicates muscarinic M1 receptors in the pharmacotherapy of the disease.
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PMID:Effects of antipsychotic medication on muscarinic M1 receptor mRNA expression in the rat brain. 1778 19

Interaction at dopamine D4 receptors may improve cognitive function, which is highly impaired in individuals with schizophrenia, but comparative studies of recent antipsychotics in cellular models of D4 receptor activation are lacking. Here, we report the in-vitro profile of over 30 ligands at recombinant hD4.4 receptors. In [35S]GTPgammaS binding experiments using membranes of CHO-hD4.4 cells, apomorphine, preclamol and the selective D4 agonists, ABT724, CP226269, Ro-10-5824 and PD168077, behaved as partial agonists (Emax 20-60% vs. dopamine), whereas L745870 and RBI257, displayed antagonist properties. The 'conventional' antipsychotic, haloperidol and the 'atypicals', clozapine and risperidone, exhibited antagonist properties, while 'third generation' compounds bifeprunox, SLV313 and F15063, acted as partial agonists (10-30%). Aripiprazole and SSR181507 slightly stimulated [35S]GTPgammaS binding at micromolar concentrations. In Xenopus laevis oocytes co-expressing hD4.4 receptors with G-protein-coupled inwardly rectifying potassium (GIRK) channels, apomorphine, preclamol, ABT724, CP226269, and PD168077 stimulated GIRK currents (Emax 70-80%). The 5-HT1A receptor ligands, WAY100635 and flibanserin, also exhibited partial agonist activity (30% and 15%, respectively). Haloperidol, clozapine, olanzapine and nemonapride did not stimulate GIRK currents, whereas aripiprazole, bifeprunox, SLV313 and F15063, but not SSR181507, exhibited partial agonism (Emax 20-35%). In-vitro responses depended on experimental conditions: increasing NaCl concentration (30 mm to 100 mm) reduced agonist efficacy in [35S]GTPgammaS binding, whereas decreasing the amount of hD4.4 cRNA injected into oocytes (from 2.0 to 0.5 ng/oocyte) reduced agonist efficacy of several compounds. These data indicate that, unlike conventional or 'atypical' antipsychotics, several 'third generation' agents display D4 receptor partial agonism that may be sufficient to influence physiological D4 receptor activity in vivo.
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PMID:Agonist and antagonist properties of antipsychotics at human dopamine D4.4 receptors: G-protein activation and K+ channel modulation in transfected cells. 1789 83

An issue under much clinical debate is whether treatment with two antipsychotic agents simultaneously is advantageous for optimizing response in patients whose previous monotherapy with antipsychotic agents has failed. Minimal evidence supports treatment with multiple antipsychotics, even when the agents have different mechanisms of action. The standard of care for treating schizophrenia is to first use monotherapy of adequate dosage and duration, including a trial of clozapine before adding a second agent. We report the case of a 32-year-old man whose monotherapy with various antipsychotic agents failed. During attempted conversion from aripiprazole to clozapine, the patient experienced a significant reduction in psychiatric features. Despite this improvement, the patient became resistant to the clozapine titration schedule due to complaints of sedation. Aripiprazole combined with low-dose clozapine as maintenance therapy resulted in a positive clinical outcome despite a clozapine serum level that is generally considered subtherapeutic. This case emphasizes the importance of making interventions based on individual patient response.
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PMID:Augmentation of aripiprazole with low-dose clozapine. 1796 67

Aripiprazole is an atypical antipsychotic that acts as a partial agonist at the dopamine D(2) receptor. It has been mainly investigated in dopamine-based models of schizophrenia, while its effects on glutamate-based paradigms have remained to be further characterized. Due to its unique mechanism of action, aripiprazole has also been considered as a replacement medication for psychostimulant abuse. Thus, in the present study we tested the hypothesis that aripiprazole would prevent the motor hyperactivity induced by psychostimulant and psychotomimetic drugs that act either by dopaminergic or glutamatergic mechanisms. Male Swiss mice received injections of aripiprazole (0.1-1 mg/kg) followed by drugs that enhance the dopamine-mediated neurotransmission, amphetamine (3 mg/kg) or cocaine (5 mg/kg), or by glutamate NMDA-receptor antagonists, ketamine (60 mg/kg) or MK-801 (0.4 mg/kg). Independent groups also received aripiprazole (0.1-1 mg/kg) or haloperidol (0.5 mg/kg) and were tested for catalepsy. All doses of aripiprazole were effective in preventing the motor stimulant effects of amphetamine and cocaine. Moreover, the higher dose also prevented the effects of ketamine and MK-801. The present study reports the effects of aripiprazole in dopaminergic and glutamatergic models predictive of antipsychotic activity, suggesting that both may be useful for screening novel partial agonists with antipsychotic activity. It also shows that aripiprazole may prevent the acute effects of psychostimulant drugs without significant motor impairment.
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PMID:Aripiprazole, an atypical antipsychotic, prevents the motor hyperactivity induced by psychotomimetics and psychostimulants in mice. 1802 64

Aripiprazole is a novel atypical antipsychotic that is approved in the US for use in adolescents with schizophrenia. In adolescents with schizophrenia, oral aripiprazole 10 or 30 mg/day lead to significantly greater reductions than placebo in the Positive and Negative Syndrome Scale (PANSS) total score from baseline to 6 weeks, according to findings from a randomized, double-blind, multicenter trial (n = 302). In addition, aripiprazole 10 or 30 mg/day recipients had significantly greater improvements in the PANSS positive subscale and Clinical global Impression-Severity and -Improvement scale scores than placebo recipients, and a significantly greater improvement in the PANSS negative subscale score was seen with aripiprazole 10 mg/day than with placebo. Aripiprazole was generally well tolerated in adolescents with schizophrenia, with most adverse events being of mild to moderate severity. Clinically significant weight gain (> or = 7% as defined by the US FDA) occurred in 4.0% of aripiprazole 10 mg/day recipients, 5.2% of aripiprazole 30 mg/day recipients, and 1% of placebo recipients. The mean weight change was significantly different in aripiprazole and placebo recipients (0, +2, and -0.8 kg in aripiprazole 10 mg/day, aripiprazole 30 mg/day, and placebo recipients, respectively).
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PMID:Aripiprazole: in adolescents with schizophrenia. 1805 12

Aripiprazole (OPC-14597) is an antipsychotic with a unique pharmacology as a dopamine D2 receptor partial agonist, which has been demonstrated to reduce symptoms of schizophrenia. To further profile this compound in preclinical models, we examined aripiprazole-induced activity changes as measured by pharmacological magnetic resonance imaging (MRI) and characterized the drug in several rodent models of motor behaviors and of psychosis. Continuous arterial spin labeling MRI measuring blood perfusion (as an indirect measure of activity) reveals that aripiprazole dose-dependently decreased brain activity in the entorhinal piriform cortex, perirhinal cortex, nucleus accumbens shell, and basolateral amygdala. While no deficits were observed in the rotarod test for motor coordination in the simpler (8 RPM) version, in the more challenging condition (16 RPM) doses of 10 and 30mg/kg i.p. produced deficits. Catalepsy was seen only at the highest dose tested (30mg/kg i.p.) and only at the 3 and 6h time points, not at the 1h time point. In pharmacological models of psychosis, 1-30mg/kg aripiprazole i.p. effectively reduced locomotor activity induced by dopamine agonists (amphetamine and apomorphine), NMDA antagonists (MK-801 and phencyclidine (PCP)), and a serotonin agonist (2,5-dimethoxy-4-iodoamphetamine (DOI)). However, aripiprazole reversed prepulse inhibition deficits induced by amphetamine, but not by any of the other agents tested. Aripiprazole alters brain activity in regions relevant to schizophrenia, and furthermore, has a pharmacological profile that differs for the two psychosis models tested and does not match the typical or atypical psychotics. Thus, D2 partial agonists may constitute a new group of antipsychotics.
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PMID:Effects of aripiprazole/OPC-14597 on motor activity, pharmacological models of psychosis, and brain activity in rats. 1805 53

Studies have found that a large percentage of depressed patients may have limited response and remission rates when treated with traditional antidepressants. Options for augmenting antidepressant treatment include buspirone, lithium, and triiodothyronine. There are also increasing data concerning the use of atypical antipsychotics as augmenting agents in the treatment of unipolar, nonpsychotic, treatment-resistant depression. Aripiprazole has recently received an indication from the U.S. Food and Drug Administration (FDA) for adjunctive treatment in unipolar, nonpsychotic depression, the first indication of its kind, after two double-blind trials; doses were slightly lower than those recommended for monotherapy in schizophrenia or bipolar disorder. Olanzapine and risperidone have several controlled clinical trials indicating the efficacy of both of these agents, generally at low doses. One trial of quetiapine suggested that it may not be effective in the treatment of unipolar, nonpsychotic depression. One open-label trial of ziprasidone indicated some efficacy. According to these results, aripiprazole, olanzapine, and risperidone are reasonable choices as augmentation agents, with only aripiprazole currently having an FDA indication for this use. Given the preliminary results, double-blind, placebo-controlled trials with quetiapine and ziprasidone are needed, as well as studies comparing atypical antipsychotic agents with traditional augmentation agents in the treatment of depression.
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PMID:Augmentation of antidepressants with atypical antipsychotics: a review of the current literature. 1821 1

Aripiprazole, a partial dopaminergic agonist, represents a well-tolerated and effective addition to the antipsychotic armamentarium. However, accumulated data indicates that aripiprazole may still induce extrapyramidal side effects (EPS) in susceptible patients. Guidelines for treating schizophrenia have consistently recommended antipsychotic monotherapy. Nevertheless, in certain clinical situations, a thorough evaluation of the benefit/risk ratio suggests that combinations of antipsychotic agents may improve treatment efficacy and tolerability. We report a schizophrenic patient for whom sequential administration of aripiprazole and risperidone induced severe EPS, and subsequent combination therapy with of clozapine and aripiprazole achieved adequate symptom control and markedly reduced EPS.
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PMID:Combined low-dose clozapine with low-dose aripiprazole in a schizophrenic patient. 1830 78


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