Atypical antipsychotics: matching receptor profile to individual patient's clinical profile

Understanding common pharmacologic and clinical "class" actions associated with atypical antipsychotics certainly reveals how these agents are alike, but what about unique differences from one agent to another? Atypical antipsychotics are also a heterogeneous group of agents that have complex pharmacologic entities, acting upon multiple dopamine receptors (D2, D1, D3, and D4) and multiple serotonin receptors (5-HT2A, 5-HT2C, 5-HT1A, and 5-HT1D, among others). Atypical antipsychotics also interact with noradrenergic (alpha 1- and alpha 2-adrenergic receptor blockade), histaminergic (H1-receptor blockade), and cholinergic (muscarinic M1 blockade) neurotransmitter systems as well as with monoamine (D, 5-HT, and norepinephrine reuptake blockade) transporters. However, no two atypical antipsychotics possess the same portfolio of actions upon all of these additional neurotransmitter systems.

Mechanism of action of aripiprazole predicts clinical efficacy and a favourable side-effect profile

The antipsychotic efficacy of aripiprazole is not generally associated with extrapyramidal symptoms, cardiovascular effects, sedation or elevations in serum prolactin that characterize typical or atypical antipsychotics. The aim of this study was to clarify the mechanism of action of aripiprazole that underlies its favourable clinical profiles. The preclinical efficacy and side-effect profiles of aripiprazole were evaluated using several pharmaco-behavioural test systems in mice and rats, both in vivo and ex vivo, and compared with those of other conventional and atypical antipsychotics. Each of the antipsychotics induced catalepsy and inhibited apomorphine-induced stereotypy. The catalepsy liability ratios for these drugs were 6.5 for aripiprazole, 4.7 for both olanzapine and risperidone. The ptosis liability ratios for aripiprazole, olanzapine and risperidone were 14, 7.2 and 3.3, respectively. Aripiprazole slightly increased DOPA accumulation in the forebrain of reserpinised mice, reduced 5-HTP accumulation at the highest dose and exhibited a weaker inhibition of 5-methoxy-N,N-dimethyl-tryptamine-induced head twitches. Aripiprazole did not inhibit physostigmine- or norepinephrine-induced lethality in rats. In conclusion, aripiprazole shows a favourable preclinical efficacy and side-effect profile compared to a typical antipsychotics. This profile may result from its high affinity partial agonist activity at D2 and 5-HT1A receptors and its antagonism of 5-HT2A receptors.

Aripiprazol - Pharmakologie eines neuen atypischen Antipsychotikums

Aripiprazole is an atypical antipsychotic agent with an intrinsic dopamineagonist activity of 30 %. Aripiprazole exerts additional partial agonist action on 5-HT (1A) receptors and has antagonist properties at 5-HT (2A) receptors. Controlled studies demonstrated an effectiveness in acute relapse of schizophrenic psychosis, chronical schizophrenic and schizoaffective disorders. Aripiprazole was effective in the treatment of productive psychotic and negative symptoms. Compared to other antipsychotics aripiprazole demonstrated a favourable profile of side effects: only slight changes of body weight, mild extrapyramidal symptoms, no prolactin elevation and no significant changes in QTc interval. The efficacy in the long term treatment of schizophrenia seems to be similar to other antipsychotics (e. g. olanzapine). The first evaluations of studies with patients with bipolar disorders showed a significant efficacy in the treatment of mania.

The use of novel antipsychotics in the older patient with neurodegenerative disorders in the long-term care setting

Treating older patients with neurodegenerative disorders involves numerous challenges. The older patient population is expected to increase appreciably in the coming years; thus, there will be increasing numbers of these individuals requiring treatment. As a result, the appropriate choice of psychopharmacologic agents becomes an important decision in treating older patients with atypical antipsychotics. The atypical antipsychotic medications are replacing the high-potency conventional antipsychotics in the long-term care setting because of the lower risks of side effects. For instance, atypical antipsychotics have lower rates of extrapyramidal side effects and tardive dyskinesia. Double-blind placebo-controlled trials examining the use of risperidone and olanzapine have been published and indicate that both agents safely and effectively reduce agitation symptoms in long-term care patients with neurodegenerative disorders. For instance, based on these studies, the doses that appear efficacious in treating behavioral agitation in dementia are 0.5 to 1.5 mg per day of risperidone and 5 to 10 mg per day of olanzapine. In addition, there are open-label studies examining the use of quetiapine, which suggest that this agent is also safe and efficacious in patients with dementia. Doses used range approximately from 25 to 350 mg per day. Very few studies are available examining the newest atypical antipsychotics, ziprasidone and aripiprazole, in patients with neurodegenerative disorders. These studies do suggest that ziprasidone and aripiprazole are worth further study in the long-term care setting.

[Psychotropics and weight gain]

Weight overload and obesity became these last years a major health problem. However gain weight is a frequent side effect of a large number of psychotropics. This article proposes to discuss this potential while reviewing various molecules. This reveals that the atypical antipsychotics are most likely to induce weight gain, in particular clozapine and olanzapine. The tricyclic antidepressants and mirtazapine come next, with the majority of the mood stabilizers. The old antipsychotics seem to involve less gain of weight. The SSRI make lose weight in the first weeks of treatment, but induce a moderate weight gain on the long term.

Efficacy of atypical antipsychotics in elderly patients with dementia

Pharmacotherapy in patients with dementia aims to improve distressing behavioral and psychological signs of dementia after nonpharmacologic interventions fail, without causing unacceptable side effects or exacerbating underlying cognitive impairment. We review data describing risperidone (3 published placebo-controlled trials), olanzapine (1 abstract regarding a placebo-controlled trial and a published placebo-controlled trial), quetiapine (1 published open-label trial and an abstract regarding a placebo-controlled trial), and aripiprazole (1 abstract regarding a placebo-controlled trial). For example, a 12-week study of risperidone in patients with Alzheimer's disease showed a dose-related improvement in psychosis and agitation. The frequency of extrapyramidal symptoms (EPS) was also significantly greater in patients receiving the highest doses. A 6-week study of olanzapine showed greater improvement than placebo in agitation/aggression and psychosis with doses of 5 and 10 mg/day, but not 15 mg/day, with side effects including gait disturbance and sedation at all doses. A 52-week, open-label trial of quetiapine (median dose = 138 mg/day) in elderly patients with psychosis suggested good tolerability with apparent behavioral benefit; EPS improved or remained unchanged in most patients. Limited data describing aripiprazole have shown inconclusive evidence regarding relief of psychosis in elderly patients with Alzheimer's disease-related dementia, with apparently good tolerability over the short term. It appears that, in the aggregate, atypical antipsychotics are efficacious for treatment of agitation in dementia, with less clear impact on psychosis, but their tolerability profiles clearly differ. The National Institute of Mental Health-funded Clinical Antipsychotic Trials of Intervention Effectiveness in Alzheimer's Disease project will provide the first head-to-head comparisons of atypicals in dementia and will examine possible drug-drug differences between efficacy and effectiveness.

Aripiprazole: in acute mania associated with bipolar I disorder

Aripiprazole, an oral quinolinone (carbostyril), is a novel atypical antipsychotic that has partial agonist activity at dopamine D(2) and serotonin 5-HT(1A) receptors, and antagonist activity at 5-HT(2A) receptors. Aripiprazole had a rapid onset of action (as early as day 4) and was effective in the treatment of patients with bipolar I disorder experiencing an acute manic or mixed episode. Aripiprazole was generally significantly more effective than placebo in improving manic symptoms (as defined by a mean change in Young Mania Rating Scale Total Score) in 3-week placebo-controlled trials, and demonstrated superior effectiveness to haloperidol (response rate 50% vs 28.4% in patients remaining on treatment) in a 12-week comparative trial. The time to relapse of symptoms in stabilised patients with bipolar I disorder who previously experienced a manic episode was significantly longer with aripiprazole than with placebo in a 26-week relapse prevention study. Aripiprazole was generally well tolerated and was not associated with weight gain, serum prolactin elevation or clinically significant QTc interval prolongation. black triangle Changes from baseline in extrapyramidal symptom scale scores with aripiprazole were small (<0.5 units), but generally significantly greater than with placebo in one of the 3-week trials. In the 12-week trial, changes from baseline were significantly smaller with aripiprazole than with haloperidol.

The novel antipsychotic aripiprazole is a partial agonist at short and long isoforms of D2 receptors linked to the regulation of adenylyl cyclase activity and prolactin release

Aripiprazole is a novel antipsychotic with a unique mechanism of action, which differs from currently marketed typical and atypical antipsychotics. Aripiprazole has been shown to be a partial agonist at the D(2) family of dopamine (DA) receptors in biochemical and pharmacological studies. To demonstrate aripiprazole's action as a partial D(2) agonist in pituitary cells at the molecular level, we retrovirally transduced the short (D(2S)) and the long (D(2L)) form of the human DA D(2) receptor gene into a rat pituitary cell line, GH4C1. [(3)H]-raclopride saturation binding analyses revealed a B(max) value approximately four-fold higher at D(2S) receptor-expressing GH4C1 cells than at D(2L) receptor-expressing GH4C1 cells, while a K(d) value was similar. Aripiprazole inhibited forskolin-stimulated release of prolactin in both D(2S) and D(2L) receptor-expressing GH4C1 cells, whereas the maximal inhibition of prolactin release was less than that of DA. Similarly, aripiprazole partially inhibited forskolin-induced cAMP accumulation in both D(2) receptor-expressing cells. Aripiprazole antagonized the suppression attained by DA (10(-7) M) in both D(2) receptor-expressing cells and, at the maximal blockade of cAMP, yielded residual cAMP levels equal to those produced by aripiprazole alone. These results indicate that aripiprazole acts as a partial agonist at both D(2S) and D(2L) receptors expressed in GH4C1 cells. These data may explain, at least in part, the observations that aripiprazole shows a novel antipsychotic activity with minimal potential for adverse events including no significant increase of serum prolactin levels in clinical studies.

Aripiprazole: review of its pharmacology and therapeutic use in psychiatric disorders

The discovery of antipsychotic medications has revolutionized the treatment of schizophrenia and other psychotic disorders. However, side effects such as extrapyramidal symptoms (EPS) and tardive dyskinesia (TD), electrocardiogram (ECG) changes, weight gain, and metabolic disturbances indicate the continued need to develop new agents. The introduction of atypical drugs such as clozapine, risperidone, olanzapine, quetiapine, and ziprasidone has widened our choices. This article provides an overview of the pharmacology, efficacy, and techniques for the clinical use of aripiprazole, a novel agent with a unique pharmacological profile.

Aripiprazole, a novel antipsychotic drug, preferentially increases dopamine release in the prefrontal cortex and hippocampus in rat brain

Aripiprazole,7-(4-[4-(2,3-dichlorophenyl)-1-piperazinyl]butyloxy)-3,4-dihydro-carbostycil (OPC-14597), a novel atypical antipsychotic drug, is a dopamine D2 receptor partial agonist with functional 5-HT2A receptor antagonist, and 5-HT1A receptor partial agonist properties as well. Other atypical antipsychotic drugs, e.g. clozapine, but not typical antipsychotic drugs, e.g. haloperidol, produce significant increases in dopamine and acetylcholine release in the medial prefrontal cortex in rats, effects believed to be related to the ability to improve cognitive function. The increase in the medial prefrontal cortex dopamine release by the atypical antipsychotic drugs has been shown to be partially inhibited by N-[2[4-)2-methoxyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100635), a selective 5-HT1A receptor antagonist. Aripiprazole, 0.1 and 0.3 mg/kg, significantly increased dopamine release in the hippocampus. Moreover, aripiprazole, 0.3 mg/kg, slightly but significantly increased dopamine release in the medial prefrontal cortex but not in the nucleus accumbens. These increases were significantly inhibited by WAY100635. By contrast, aripiprazole, 3.0 mg/kg and 10 mg/kg, significantly decreased dopamine release in the nucleus accumbens but not the medical prefrontal cortex. However, aripiprazole 10 mg/kg significantly decreased dopamine release in the both regions. Aripiprazole had no effect on acetylcholine release in the medial prefrontal cortex, hippocampus, or nucleus accumbens at any dose, except for 3.0 mg/kg, which decreased acetylcholine release in the nucleus accumbens only. Aripiprazole, 0.3 mg/kg, transiently potentiated haloperidol (0.1 mg/kg)-induced dopamine release in the medial prefrontal cortex but inhibited that in the nucleus accumbens. The present study demonstrated that aripiprazole, at low doses of 0.1 and 0.3 mg/kg, increases dopamine release in the medial prefrontal cortex and hippocampus. It also suggests that the function of both the medial prefrontal cortex and hippocampus may contribute to the ability of aripiprazole to improve negative symptom and cognition.

Aripiprazole for drug-induced psychosis in Parkinson disease: preliminary experience

Aripiprazole is the newest atypical antipsychotic (AA) drug to be released in the US. It is the only AA that is a partial agonist at the D2 and 5HT1a receptors and an antagonist at 5HT2a receptors. It also has a high 5HT2/D2 ratio and may therefore carry a low risk of extrapyramidal side effects and alleviate psychosis in Parkinson-vulnerable populations. We report our preliminary experience in 8 patients with probable Parkinson disease (PD) treated with aripiprazole for drug-induced psychosis. Two patients were neuroleptic-naive, 5 patients were "quetiapine failures", and 1 patient was switched from olanzapine to aripiprazole. Aripiprazole was started at 5 mg to 10 mg a day and slowly increased over 3 to 7 days until side effects or improvement of psychosis occurred. Only 2 out of 8 patients experienced near complete resolution of their psychosis using aripiprazole. The other six patients discontinued aripiprazole within 40 days, 2 of whom discontinued due to motor worsening. Our preliminary experience with aripiprazole is mixed but not very encouraging. Controlled studies are needed to evaluate aripiprazole in parkinsonian patients.

Dopamine partial agonists: a new class of antipsychotic

This review examines the development of dopamine partial agonists as a new class of antipsychotic agents. Partial agonists have a lower intrinsic activity at receptors than full agonists, allowing them to act either as a functional agonist or a functional antagonist, depending on the surrounding levels of naturally occurring neurotransmitter (full agonist). In the absence of a full agonist, partial agonists show functional agonist activity, binding to the receptor to produce a response. In the presence of a full agonist, partial agonists show functional antagonist activity, as receptor binding reduces the response from that seen with the full agonist. A partial agonist at dopamine D(2) receptors therefore offers an attractive option for the treatment of schizophrenia. It should act as a functional antagonist in the mesolimbic dopamine pathway, where excessive dopamine activity is thought to cause positive symptoms, but show functional agonist activity in the mesocortical pathway, where reduced dopamine activity is thought to be associated with negative symptoms and cognitive impairment. In addition, it should avoid the complete blockade of the nigrostriatal or tuberoinfundibular pathways, associated with extrapyramidal symptoms (EPS) and elevated prolactin levels, respectively. Clinical trials with aripiprazole - a new antipsychotic, which shows partial agonist activity at D(2) receptors and serotonin 5-HT(1A) receptors, and antagonist activity 5-HT(2A) receptors - have demonstrated the value of this treatment approach. Aripiprazole produced significant improvements in positive and negative symptoms in short- and long-term studies of patients with schizophrenia or schizoaffective disorder. Improvements occurred rapidly after the start of treatment, and were sustained throughout studies lasting up to 52 weeks. Significantly more patients responded to aripiprazole treatment than to haloperidol in the 52-week study, and aripiprazole-treated patients showed significantly greater improvements in negative and depressive symptoms than those receiving haloperidol. Aripiprazole treatment was well tolerated in both short- and long-term studies, showing a low liability for EPS and hyperprolactinemia, a lack of QTc prolongation, and minimal weight gain or sedation. In conclusion, the findings from clinical studies of aripiprazole show that dopamine partial agonists offer a novel, effective and well-tolerated treatment approach for patients with schizophrenia.

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.

The Texas Medication Algorithm Project antipsychotic algorithm for schizophrenia: 2003 update

BACKGROUND

The Texas Medication Algorithm Project (TMAP) has been a public-academic collaboration in which guidelines for medication treatment of schizophrenia, bipolar disorder, and major depressive disorder were used in selected public outpatient clinics in Texas. Subsequently, these algorithms were implemented throughout Texas and are being used in other states. Guidelines require updating when significant new evidence emerges; the antipsychotic algorithm for schizophrenia was last updated in 1999. This article reports the recommendations developed in 2002 and 2003 by a group of experts, clinicians, and administrators.

METHOD

A conference in January 2002 began the update process. Before the conference, experts in the pharmacologic treatment of schizophrenia, clinicians, and administrators reviewed literature topics and prepared presentations. Topics included ziprasidone's inclusion in the algorithm, the number of antipsychotics tried before clozapine, and the role of first generation antipsychotics. Data were rated according to Agency for Healthcare Research and Quality criteria. After discussing the presentations, conference attendees arrived at consensus recommendations. Consideration of aripiprazole's inclusion was subsequently handled by electronic communications.

RESULTS

The antipsychotic algorithm for schizophrenia was updated to include ziprasidone and aripiprazole among the first-line agents. Relative to the prior algorithm, the number of stages before clozapine was reduced. First generation antipsychotics were included but not as first-line choices. For patients refusing or not responding to clozapine and clozapine augmentation, preference was given to trying monotherapy with another antipsychotic before resorting to antipsychotic combinations.

CONCLUSION

Consensus on algorithm revisions was achieved, but only further well-controlled research will answer many key questions about sequence and type of medication treatments of schizophrenia.

Aripiprazole (OPC-14597) fully substitutes for the 5-HT1A receptor agonist LY293284 in the drug discrimination assay in rats

RATIONALE

Aripiprazole (OPC-14597) is a novel atypical antipsychotic drug with a low incidence of side effects. The therapeutic action of aripiprazole has been attributed to its unique agonist/antagonist effects at D(2) dopamine receptors; however, aripiprazole also has significant in vitro affinity at 5-HT(1A) receptors.

OBJECTIVES

The 5-HT(1A) agonist property of aripiprazole has so far not been evaluated in any in vivo assay.

METHODS

Thirteen male Sprague Dawley rats trained to discriminate the 5-HT(1A) agonist LY 293284 (75 nmol/kg) from saline, using a fixed ratio (FR) 50 schedule of food-reinforcement in a two-lever operant-conditioning task, were used to evaluate the behavioral effect of aripiprazole at 5-HT(1A) receptors.

RESULTS

Aripiprazole fully mimicked LY 293284 in a drug-discrimination assay with an ED(50) of 1.39 micromol/kg (0.62 mg/kg). In combination tests, aripiprazole did not block the LY 293284 cue but at 8.92 micromol/kg (4 mg/kg) significantly reduced the response rate by lowering the threshold for induction of the 5-HT syndrome produced by the training dose of LY 293284. Moreover, the selective 5HT(1A) receptor antagonist WAY 100635 was able to block the substitution of aripiprazole in LY-293284 trained rats.

CONCLUSION

Although the efficacy of aripiprazole against the positive symptoms of schizophrenia may be related to its dopamine receptor interactions, it seems possible that its atypical profile may derive, at least in part, from its 5-HT(1A) agonist effect, rather than from unusual D(2) receptor properties.

Excessive Somnolence from Aripiprazole in a Child

A 9-year-old girl was hospitalized with prolonged somnolence that began 3.5 hours after a single 15-mg dose of aripiprazole. After extensive workup, physical examinations were unremarkable, and all laboratory test results were within normal limits. The patient's extreme somnolence was attributed to aripiprazole, a new atypical antipsychotic prescribed for oppositional defiant disorder. In clinical trials, somnolence has been reported with a frequency of approximately 11%. However, the somnolence experienced by this child was severe, requiring 24-hour hospitalization for observation. Although a recent dose-finding study in 22 pediatric patients (> or = 6 yrs old) described weight-based dosages that were safe and well tolerated, dosing of aripiprazole in children has not been well established. Further studies are needed to identify optimal dosing of aripiprazole in pediatric patients.

Aripiprazole in an adult with Asperger disorder

OBJECTIVE

To report a case of aripiprazole-responsive adult Asperger disorder.

CASE SUMMARY

A 34-year-old white man with lifelong, disabling Asperger disorder and a 20-year history of failed psychotherapeutic and pharmacologic interventions was prescribed aripiprazole, with dramatic symptomatic improvement.

DISCUSSION

Multiple prior pharmacologic efforts over several years aimed predominantly at altering serotonin and dopamine neurotransmission resulted in treatment failure due to intolerable adverse effects, exacerbation of underlying symptoms, or nonresponse. Aripiprazole, with a complex profile of neurotransmitter affinities, has produced significant core symptom changes. Improved sociability; increased self-awareness; reduced rigidity, anxiety, and irritability; and reduced preoccupation with circumscribed esoteric interests are among the effects noted.

CONCLUSIONS

Previously intractable Asperger disorder symptoms in a 34-year-old man were ameliorated with aripiprazole.

Similarities and differences among antipsychotics

Most antipsychotic drugs act equivalently and potently on the symptoms of schizophrenia, with clozapine as the notable exception. Negative symptoms and cognitive deficits are strongly associated with poor prognosis; some reports suggest that these symptoms respond better to second- than to first-generation antipsychotics. Although second-generation antipsychotics exert their action through a blockade of dopamine and serotonin receptors (and some have a more complex action), each has a different set of pharmacologic characteristics, including side effects. Due to the differences among antipsychotics available today, optimizing treatment for individual patients requires choosing the most appropriate drug and, if necessary, switching to a different drug if the first proves unsatisfactory. The treating physician must carefully match the diverse needs of schizophrenic patients with the varied characteristics of the second-generation antipsychotics.

Aripiprazole, a Novel Atypical Antipsychotic Drug

Before the 1990s, treatment of psychoses centered on conventional agents whose tolerability was limited by extrapyramidal side effects (EPS). The past decade has seen the emergence of a newer generation of antipsychotic agents, first with clozapine and followed shortly by risperidone, olanzapine, quetiapine, and ziprasidone. These agents have been touted as providing better negative symptom efficacy, less impaired cognition, and lower risk of extrapyramidal syndromes. However, evolving evidence suggests that several drugs in this class may be associated with significant weight gain and lipid abnormalities. Aripiprazole, a new atypical antipsychotic drug, displayed efficacy similar to that of haloperidol and risperidone and superior to that of placebo in numerous clinical trials. Aripiprazole does not cause significant prolactin elevation and is associated with a low rate of clinically significant weight gain compared with other atypical antipsychotics. Patients receiving aripiprazole experienced EPS at a rate similar to that seen with placebo. Aripiprazole provides a new treatment option with limited adverse effects for patients in need of antipsychotic therapy.

Naturalistic Studies of Second Generation Antipsychotics in the Treatment of Schizophrenia

Undoubtedly, the pharmacological treatment of schizophrenia has changed dramatically over the last 10 years. Large, double-blind, placebo-controlled trials have ushered the availability of each new antipsychotic. However, there has been an information lag because of the relative paucity of long term, comparative studies among second-generation antipsychotics. While we await such evidence, naturalistic studies have helped to provide useful information on the pattern of use, patient response, and tolerability of these new agents in clinical practice. This review provides an account of representative studies for each second generation antipsychotic, which illustrate the contributions of naturalistic studies to our understanding of the evolving pharmacotherapy of schizophrenia.

Schizophrenia: From Dopamine to Glutamate and Back

The first part of the present review describes the exciting journey of dopamine stabilizers, starting in the early eighties with the development of the partial dopamine agonist (-)-3-PPP of phenylpiperidine structure, via various compounds with aminotetraline structure with preferential autoreceptor antagonist properties, and then back again to phenylpiperidine compounds carrying substituents on the aromatic ring that transformed them from partial dopamine agonists to partial dopamine receptor antagonists, such as OSU6162. OSU6162 was brought to the clinic and has in preliminary trials showed antidyskinetic and antipsychotic efficacy. The second part of this review describes results from a hypoglutamatergia mouse model for cognitive symptoms of schizophrenia, where we have tested traditional neuroleptics, new generation antipsychotics with marked 5-HT2 vs dopamine D2 receptor blockade as well as a dopamine stabilizer belonging to the partial dopamine receptor antagonist category.

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.

Aripiprazole for schizophrenia

BACKGROUND

Treatment of people with schizophrenia using older typical antipsychotic drugs such as haloperidol can be problematic. Many fail to respond and more experience disabling adverse effects. Aripiprazole is said to be one of a new generation of atypical antipsychotics with good antipsychotic properties and minimal adverse effects.

OBJECTIVES

To evaluate the effects of aripiprazole for people with schizophrenia and schizophrenia-like psychoses.

SEARCH STRATEGY

The reviewers searched the Cochrane Schizophrenia Group's Register (May 2003) which is based on regular searches of BIOSIS, CENTRAL, CINAHL, EMBASE, MEDLINE and PsycINFO. References of all identified studies were inspected for further trials. The authors contacted relevant pharmaceutical companies, the FDA and authors of trials for additional information.

SELECTION CRITERIA

All clinical randomised trials comparing aripiprazole with placebo, typical or atypical antipsychotic drugs for schizophrenia and schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

We extracted data independently. For homogenous dichotomous data we calculated random effects, relative risk (RR), 95% confidence intervals (CI) and, where appropriate, numbers needed to treat (NNT) on an intention-to-treat basis. For continuous data, we calculated weighted mean differences (WMD).

MAIN RESULTS

Despite the fact that 4125 people participated in ten randomised aripiprazole studies, we were unable to extract any usable data on death, service outcomes, general functioning, behaviour, engagement with services, satisfaction with treatment; economic outcomes or cognitive functioning. Study attrition was very large and data reporting poor. Compared with placebo, aripiprazole significantly decreased relapse in both the short and medium term (n=300, 1 RCT, RR 0.66 CI 0.53 to 0.81, NNT 5 CI 4 to 8). It also produced better compliance with study protocol (n=1348, 5 RCTs, RR 0.66 CI 0.49 to 0.88, NNT 15 CI 10 to 41). Aripiprazole may decrease prolactin levels below that expected from placebo (n=305, 1 RCT, RR 0.32 CI 0.13 to 0.81, NNT 14 CI 11 to 50). Compared with typical antipsychotics there were no significant benefits for aripiprazole with regards to global state, mental state, quality of life or leaving the study early. Both groups reported similar rates of adverse effects, including akathisia (RR 0.44 CI 0.17 to 1.12) and general extrapyramidal effects (RR 0.53 CI 0.18 to 1.53). Aripiprazole did however cause more insomnia than perphenazine (n=300, 1 RCT, RR 2.23 CI 1.57 to 3.18, NNH 4 CI 3 to 9) and less need for antiparkinson drugs than 10-20mg/day haloperidol (n=1854, 4 RCTs, RR 0.45 CI 0.33 to 0.60, NNT 4 CI 3 to 5). When compared with olanzapine and risperidone, aripiprazole was no better or worse on outcomes of global state and leaving the study early. The rates of adverse effects were also similar, with the exception of less elevation of prolactin (n=301, 1 RCT, RR 0.04 CI 0.02 to 0.08, NNT 2) and less prolongation of the average QTc (30mg/day) (n=200, 1 RCT, WMD -10.0, CI -16.99 to -3.01) compared with risperidone.

REVIEWERS' CONCLUSIONS

Aripiprazole may be effective for the treatment of schizophrenia, but it is not much different from typical antipsychotics and atypical antipsychotics with respect to treatment response, efficacy or tolerability. In comparison with typical antipsychotics, aripiprazole may have a higher risk of insomnia, but in comparison to atypical antipsychotics, less risk of raised prolactin and prolongation of the QTc interval. Clearly reported pragmatic short, medium and long term randomised controlled trials should be carried out to determine its position in everyday clinical practice.

Aripiprazole possibly worsens psychosis

Aripirazole is a novel antipsychotic that functions as a partial agonist at the dopamine D2 receptor and, thus, might theoretically worsen psychosis. We report a series of four clinical cases of exacerbation of psychosis related to initiation of aripiprazole therapy. Cases 1 and 2 demonstrated the worsening of psychosis following initiation of aripiprazole (15-30 mg daily) while tapering off the previous atypical antipsychotic. Cases 3 and 4 demonstrated worsening of psychosis following the addition of aripiprazole (15-30 mg daily) to an atypical antipsychotic. In two out of the four cases, discontinuation of arpiprazole resulted in improvement of psychotic symptoms. Although the cases presented are suggestive of a relationship between initiation of aripiprazole therapy and worsening of psychosis, further research is needed to clarify any potential association.

In vivo effects of aripiprazole on cortical and striatal dopaminergic and serotonergic function

In vivo microdialysis was used to monitor the effects of oral aripiprazole and olanzapine on basal extracellular concentrations of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA) in the medial prefrontal cortex and striatum of conscious, freely moving rats. Acute aripiprazole administration did not affect dopamine output, but produced moderate increases in DOPAC and HVA concentrations, in medial prefrontal cortex or striatum of drug-naïve rats. Similarly, aripiprazole did not affect dopamine output but produced moderate elevations in DOPAC and HVA concentrations in the striatum of chronic aripiprazole-pretreated rats. Olanzapine produced comparatively larger elevations in dopamine, DOPAC, and HVA in both regions, which, in the striatum, were diminished after chronic olanzapine exposure. Aripiprazole reduced extracellular 5-HIAA concentrations in the medial prefrontal cortex and striatum of drug-nai;ve rats, but not in chronic aripiprazole-pretreated rats. Together, these data provide in vivo evidence of aripiprazole-induced changes in forebrain dopaminergic and serotonergic function that may reflect its partial agonist activity at presynaptic dopamine D(2) and 5-HT(1A) receptors and antagonist activity at 5-HT(2A) receptors.

The case for atypical antipsychotics in bipolar disorder

As the opening scenario illustrates about Mary and Bob, bipolar disorder can be devastating to individuals and families. Managing symptoms through psychotropic medications can help people with mental illness better manage their lives. Our brief review of the current research supports the effectiveness of atypical antipsychotic medications and, therefore, supports their use in treating bipolar disorder.

Dopamine receptor downregulation: an alternative strategy for schizophrenia treatment

Schizophrenia is a common and devastating illness. The cause of schizophrenia is still unknown and the simplest formulation of the "Dopamine hypothesis" posits that schizophrenia results from dopaminergic hyperactivity. Under the hypothesis of dopaminergic hyperactivity in schizophrenia, antipsychotics blocking the dopamine D2 receptor (DRD2) and other approaches to reduce dopamine (DA) transmission have been used to treat schizophrenia. I propose that dopamine receptor (DR) downregulation could be an alternative strategy to compromise dopaminergic overactivity implicated in the pathogenesis of schizophrenia. Agonist-induced receptor downregulation includes receptor proteolysis, modulation of receptor gene transcription and affecting of RNA stability. These processes cause a decrease of existing receptors and reduction of receptor synthesis. This hypothesis could explain the antipsychotic mechanisms of DA agonists or partial agonists, like aripiprazole. It is suggested that the development of agents that increase DR downregulation could be an alternative strategy for schizophrenia treatment.

Drug development for anxiety disorders: new roles for atypical antipsychotics

Anxiety disorders are prevalent and frequently comorbid with depression. Rates of response and remission for anxiety disorders are low despite marked improvements in treatment in the past several decades. Antidepressants and anxiolytics remain the most frequently prescribed agents for anxiety disorders, but the numbers of prescriptions for novel forms of therapy, such as anticonvulsants and atypical antipsychotics are increasing. For the atypical antipsychotics, agonist activity at the 5-HT1A receptor has been hypothesized to translate into anxiolytic effects. A small, but growing, literature suggests that atypical antipsychotics are useful as augmentation therapy for treatment of refractory anxiety disorders. The next generation antipsychotic, aripiprazole, has a unique mechanism of action (ie, combined D2 and 5-HT1A partial agonist and 5-HT2A antagonist) and improves depressive and depressive/anxiety symptoms in patients with schizophrenia. Further studies examining the effect of aripiprazole and other atypical antipsychotic drugs on depressive and anxiety symptoms in patients with refractory anxiety disorders are warranted. Psychopharmacology Bulletin. 2004;38(Suppl 1): 38-45.

Aripiprazole

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of aripiprazole are discussed. Aripiprazole is a third-generation antipsychotic agent indicated for use in the treatment of schizophrenia. Unlike other antipsychotics, aripiprazole demonstrates mixed D2 and serotonin (5-HT1A) receptor agonist-antagonist activity that is hypothesized to improve schlzophrenia's positive and negative symptoms; the drug has been referred to as a dopamine-serotonin stabilizer. Aripiprazole is well absorbed, with peak plasma concentrations occurring within three to five hours after administration. The oral availability is 87%. The mean elimination half-life is about 75 hours for aripiprazole and 94 hours for its active metabolite. In controlled, randomized, multicenter trials, aripiprazole has demonstrated efficacy in the treatment of schizophrenia comparable to that of haloperidol and superior to placebo. In a single clinical trial, aripiprazole was superior to placebo in the treatment of acute mania. The most frequent adverse effects are headache, anxiety, insomnia, nausea, vomiting, and lightheadedness. Because aripiprazole is a substrate of both cytochrome P-450 isoenzymes 3A4 and 2D6, there is a potential for other drugs to affect its metabolism. The recommended starting dosage is 10 or 15 mg daily, preferably administered with meals. Aripiprazole offers an alternative to second-generation antipsychotic agents in the treatment of schizophrenia.

haloperidol for long-term maintenance treatment following acute relapse of schizophrenia

Aripiprazole is a novel atypical antipsychotic for the treatment of schizophrenia. It is a D2 receptor partial agonist with partial agonist activity at 5-HT1A receptors and antagonist activity at 5-HT2A receptors. The long-term efficacy and safety of aripiprazole (30 mg/d) relative to haloperidol (10 mg/d) were investigated in two 52-wk, randomized, double-blind, multicentre studies (using similar protocols which were prospectively identified to be pooled for analysis) in 1294 patients in acute relapse with a diagnosis of chronic schizophrenia and who had previously responded to antipsychotic medications. Aripiprazole demonstrated long-term efficacy that was comparable or superior to haloperidol across all symptoms measures, including significantly greater improvements for PANSS negative subscale scores and MADRS total score (p<0.05). The time to discontinuation for any reason was significantly greater with aripiprazole than with haloperidol (p=0.0001). Time to discontinuation due to adverse events or lack of efficacy was significantly greater with aripiprazole than with haloperidol (p=0.0001). Aripiprazole was associated with significantly lower scores on all extrapyramidal symptoms assessments than haloperidol (p<0.001). In summary, aripiprazole demonstrated efficacy equivalent or superior to haloperidol with associated benefits for safety and tolerability. Aripiprazole represents a promising new option for the long-term treatment of schizophrenia.

Mechanism of new antipsychotic medications: occupancy is not just antagonism

Antagonism of D2-like dopamine receptors is the putative mechanism underlying the antipsychotic efficacy of psychotropic drugs. Positron emission tomographic studies suggest that the antipsychotic effect of dopamine receptor antagonists occurs within a therapeutic window between 60% and 80% (striatal) D2 receptor occupancy. The incidence of extrapyramidal side effects increases above the 80% threshold. However, the novel atypical antipsychotic drug, aripiprazole, occupies up to 95% of striatal D2-like dopamine receptors at clinical doses, and the incidence of extrapyramidal side effects with aripiprazole is no higher than with placebo. The most likely explanation for this finding is aripiprazole's weak partial agonism at D2-like dopamine receptors. This particular pharmacologic feature characterizes a new class of atypical antipsychotics that does not match the original concept of a therapeutic occupancy window for antagonist antipsychotics. When not involving pure antagonists, it implies a need to adjust the expected receptor occupancy (measured using positron emission tomography) for the therapeutic window.

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.

Aripiprazole for the prevention of relapse in stabilized patients with chronic schizophrenia: a placebo-controlled 26-week study

BACKGROUND

Aripiprazole is a novel antipsychotic for the management of schizophrenia. This study investigated the efficacy, safety, and tolerability of aripiprazole in preventing relapse in adult chronic schizophrenia patients experiencing ongoing stable symptomatology.

METHOD

In this 26-week, randomized, double-blind, placebo-controlled, parallel-group, multi-center study, 310 patients with DSM-IV schizophrenia (mean Positive and Negative Syndrome Scale [PANSS] total score = 82) were randomly assigned to receive a once-daily fixed dose of aripiprazole, 15 mg, or placebo. The primary outcome measure was time to relapse following randomization. Secondary objectives were to assess the efficacy, safety, and tolerability of aripiprazole, 15 mg, compared with placebo, in the study population. The study was conducted between Dec. 21, 2000, and Aug. 20, 2001.

RESULTS

The time to relapse following randomization was significantly (p < .001) longer for aripiprazole compared with placebo. More patients relapsed with placebo (N = 85; 57%) than aripiprazole (N = 50; 34%); the relative risk of relapse for the aripiprazole group was 0.59 (p < .001). Aripiprazole was significantly superior to placebo from baseline to endpoint in PANSS total, PANSS positive, PANSS-derived Brief Psychiatric Rating Scale, and Clinical Global Impressions-Severity of Illness scale (CGI-S) scores and demonstrated significantly better mean Clinical Global Impressions-Global Improvement scale scores (p < or = .01 for all comparisons except CGI-S: .01 < p < or = .05). Aripiprazole was well tolerated, with no evidence of marked sedation and no evidence of hyperprolactinemia or prolonged heart rate-corrected QT interval (QTc). Extrapyramidal symptoms were comparable in the aripiprazole and placebo groups. Modest mean weight loss at endpoint was evident in both groups.

CONCLUSION

Aripiprazole, 15 mg once daily, is an effective, well-tolerated treatment for prevention of relapse in patients with chronic, stable schizophrenia.

Treatment for mood and anxiety disorders: quetiapine and aripiprazole

Atypical antipsychotic agents have a broad range of therapeutic efficacy, a relatively low incidence of causing extrapyramidal adverse effects, and a low tardive dyskinesia profile. This has led to very rapid growth in the use of these compounds as broad-spectrum psychotropic agents, and it has been reported that more than 70% of prescriptions for atypical antipsychotic medications are being used for conditions other than schizophrenia. In the area of bipolar disorder, in particular, atypical antipsychotic agents appear to positively affect illness outcome, and are considered potential first-line treatment agents. Quetiapine was approved by the US Food and Drug Administration in 1997, and is currently marketed in the US to treat schizophrenia. Aripiprazole was recently approved for the treatment of schizophrenia by the US Food and Drug Administration in late 2002, and is being used increasingly in clinical settings. Recent reports suggest that quetiapine and aripiprazole are valuable additions to the psychotropic armamentarium for the treatment of mood and anxiety disorders. Data from clinical trials and clinical reports are discussed herewith.