What is an atypical antipsychotic?

Detecting biomarkers associated with antipsychotic-induced extrapyramidal syndromes by using machine learning techniques

BACKGROUND

Antipsychotic-associated extrapyramidal syndromes (EPS) are a common side effect that may result in discontinuation of treatment. Although some clinical features of individuals who develop specific EPSs are well defined, no specific laboratory parameter has been identified to predict the risk of developing EPS.

METHODS

Three hundred and ninety hospitalizations of patients under antipsychotic medication were evaluated. Machine learning techniques were applied to laboratory parameters routinely collected at admission.

RESULTS

Random forests classifier gave the most promising results to show the importance of parameters in developing EPS. Albumin has the maximum importance in the model with 4.28% followed by folate with 4.09%. The mean albumin levels of EPS and non-EPS group was 4,06 ± 0,40 and 4,24 ± 0,37 (p = 0,027) and folate level was 6,42 ± 3,44 and 7,95 ± 4,16 (p = 0,05) respectively. Both parameters showed lower levels in EPS group.

CONCLUSIONS

Our results suggest that relatively low albumin and folate levels may be associated with developing EPS. Further research is needed to determine cut-off levels for these candidate markers to predict EPS.

Molecular properties affecting fast dissociation from the D2 receptor

Dopamine D(2) receptor antagonism is the foundation of antipsychotic treatment. Antipsychotic agents vary in how fast they dissociate from the D(2) receptors. It has been proposed that the liability to exhibit side effects such as extra pyramidal symptoms may be the result of a slow rate of dissociation. Compounds with a faster rate of dissociation, while still blocking efficiently the D(2) receptors, will subsequently respond better to physiological surges in dopamine transmission. Therefore, work in our laboratories has focussed on identifying fast dissociating and selective D(2) antagonists. Biological screening was performed to measure the affinity and extent of dissociation for a large dataset of over 1800 D(2) antagonists. Subsequent univariate and multivariate statistical analysis revealed the molecular properties which differentiate fast and slow dissociating compounds. It is shown that faster dissociating antagonists are less lipophilic and have lower molecular weight. There was a clear and expected inverse relationship with extent of dissociation and binding affinity with more potent compounds tending to be slower dissociating. However, within a range of comparable affinity both fast and slow dissociating compounds were identified. After de-correlating affinity and dissociation the analysis revealed the important descriptors.

Akathisia and second-generation antipsychotic drugs

PURPOSE OF REVIEW

Akathisa is one of the most common and distressing neuroleptic-induced extrapyramidal side effects. Although it is well recognized in the context of conventional antipsychotic medications, there have been recent concerns raised by clinicians and researchers that this syndrome is overlooked in relation to second-generation or atypical antipsychotics. This review examines the recent literature relevant to second-generation antipsychotic (SGA)-induced akathisia.

RECENT FINDINGS

Recent studies using large databases clearly indicate that extrapyramidal side effects, in particular akathisia, do occur with the SGAs, although the frequency is not as high as with the conventional antipsychotics. Risk factors include use of high doses, high potency SGAs, or combinations of SGAs with other psychotropic drugs, bipolar depression, palliative care settings, and comorbid substance abuse in psychosis. The dopamine hypothesis remains plausible for understanding the pathophysiology of akathisia. There is emerging evidence that mirtazapine may be useful in the treatment of acute akathisia.

SUMMARY

Even though akathisia is less prevalent with SGAs than with the first-generation drugs, it remains clinically important and all clinicians should be conversant with its recognition and management.

Discriminative stimulus properties of atypical and typical antipsychotic drugs: a review of preclinical studies

BACKGROUND

Drug discrimination is an increasingly valuable behavioral assay for the preclinical development of antipsychotic drugs. The majority of studies have used the atypical antipsychotic clozapine because it displays robust discriminative stimulus properties and is the "prototypical" or "gold standard" atypical antipsychotic against which other antipsychotics will undoubtedly be compared for many years.

OBJECTIVES

Pharmacological mechanisms mediating the discriminative stimulus properties of antipsychotics used as training drugs and the usefulness of drug discrimination for distinguishing typical and atypical antipsychotics were reviewed.

RESULTS

Clozapine appears to have a compound cue involving antagonism of two or more receptors. While muscarinic receptor antagonism is a prominent factor for mediation of clozapine's cue in rats with a 5.0-mg/kg training dose, there are differences in clozapine's cue with a low training dose and in pigeons and mice. With a low training dose, clozapine has consistently produced full or partial generalization to atypical but not to typical antipsychotics. Although not evaluated as extensively, the atypical antipsychotics quetiapine and ziprasidone also appear to generalize to atypical but not typical antipsychotics. This has not been the case for other antipsychotic drugs (olanzapine, chlorpromazine, haloperidol) used as training drugs.

CONCLUSIONS

There are important differences in discriminative stimulus properties both between and within atypical and typical antipsychotics and across species. While low-dose clozapine discrimination in rats appears to provide a more sensitive behavioral assay for distinguishing atypical from typical antipsychotics, the extent to which clozapine's discriminative stimulus properties are predictive of its antipsychotic effects remains to be determined.

Atypicality of atypical antipsychotics

OBJECTIVE

To review the current definition of atypicality, discuss the unique features of each atypical antipsychotic, and determine whether the available drugs in this class really meet the classical definition of atypicality.

DATA SOURCES

A PubMed search was conducted to identify literature on the subject of this review, supported by additional articles based on the author's clinical knowledge and experience.

STUDY SELECTION AND DATA EXTRACTION

Relevant references were extracted and summarized in order to meet the objective of the article.

DATA SYNTHESIS

Atypical antipsychotics are considered a major advance over conventional antipsychotics, primarily because they offer effective treatment alternatives that are relatively free of extrapyramidal symptoms. In fact, the term atypicality was originally used to describe antipsychotic agents with a minimal risk of causing extrapyramidal symptoms. However, over the years the definition has been modified such that there is currently no consensus on a true definition of atypicality for these agents. Each of the atypical antipsychotics (clozapine, risperidone, olanzapine, quetiapine, ziprasidone, and aripiprazole) commercially available in the United States is unique in terms of its pharmacologic profile, differing with respect to receptor-binding affinity, mechanism of action, and adverse events. Of the available atypical antipsychotics, clozapine and quetiapine have shown the lowest propensity to cause extrapyramidal symptoms. Although the risk of extra-pyramidal symptoms is lower with risperidone and olanzapine than with conventional antipsychotics, risk increases with dose escalation. Data for ziprasidone indicate that the risk of extrapyramidal symptoms may be similar to that of risperidone and olanzapine. There is a concern of akathisia with aripiprazole; however, more experience with this agent is needed before definitive conclusions are made.

CONCLUSION

If the definition of "atypical" antipsychotic is considered to be freedom from extrapyramidal symptoms, then, based on a comprehensive review of available data and clinical experience, clozapine and quetiapine appear to be the only true atypicals.

Chronic treatment with atypical neuroleptics induces striosomal FosB/DeltaFosB expression in rats

BACKGROUND

Studies have shown that neuroleptics regulate expression of the transcription factor FosB/DeltaFosB in the striatum, including the accumbens and caudate-putamen; however, the striatum is also divided into another structural dimension, the striosome and matrix compartments. The precise distribution of FosB/DeltaFosB induced by chronic neuroleptics in these striatal compartments is poorly understood.

METHODS

Rats received either single acute injections or chronic injections of clozapine (0 or 20 mg/kg, intraperitoneally [IP]), olanzapine (0 or 5 mg/kg, IP), or haloperidol (0 or 1.5 mg/kg, IP) for 25 days. The levels and compartmental distribution of FosB/DeltaFosB were examined.

RESULTS

Chronic clozapine induced clustered FosB/DeltaFosB expression within striosomes of the caudate-putamen. This pattern was due to increased levels of FosB/DeltaFosB in striosomes within the ventrolateral caudate-putamen and reduced levels of basal FosB/DeltaFosB in the matrix in the entire caudate-putamen. In contrast, chronic haloperidol increased FosB/DeltaFosB equally within the matrix and striosomes throughout the entire caudate-putamen. Chronic olanzapine induced an intermediate pattern.

CONCLUSIONS

The relative absence of FosB/DeltaFosB expression in the matrix correlates with the lack of parkinsonism of atypical neuroleptics. Expression of FosB/DeltaFosB in the matrix may contribute to parkinsonism of typical neuroleptics.

New generation antipsychotics for first episode schizophrenia

BACKGROUND

The new generation antipsychotics are associated with a lower risk of adverse effects compared with drugs such as haloperidol. Many treatment guidelines recommend the use of new generation ('atypical') antipsychotic drugs for people with a first episode of schizophrenia.

OBJECTIVES

To examine the effects of the new generation antipsychotics for people with a first episode of schizophrenia or schizophrenia-like psychoses.

SEARCH STRATEGY

The reviewers searched the Cochrane Schizophrenia Group's register (March 2002) and the included and excluded studies tables of relevant Cochrane reviews, references of all relevant studies, contacted industry and authors of relevant studies to identify further trials.

SELECTION CRITERIA

Randomised clinical trials comparing new generation antipsychotics (amisulpride, clozapine, olanzapine, quetiapine, risperidone, sulpiride, ziprasidone, zotepine) with conventional antipsychotics for people with a first episode of schizophrenia or schizophrenia-like psychoses.

DATA COLLECTION AND ANALYSIS

Citations and, where possible, abstracts were independently inspected by three reviewers, papers ordered, re-inspected and quality assessed. We independently extracted data but excluded them if loss to follow up was greater than 50%. For homogeneous dichotomous data, we calculated the relative risk (RR), the 95% confidence interval (CI) and, where appropriate, the number needed to treat (NNT), on an intention-to-treat basis. For continuous data, reviewers calculated weighted mean differences (WMD).

MAIN RESULTS

We include two short-term studies (total n=266), one of which was a report of a sub-group of a larger study. One compared risperidone with an average of 6 mg/day haloperidol and the other olanzapine with an average of 11 mg/day haloperidol. Compared with olanzapine, significantly more people receiving haloperidol left the study early (n=83, 1 RCT, RR 0.43 CI 0.3 to 0.7, NNH 3 CI 2 to 8). This was not so for the risperidone versus haloperidol comparison (n=183, 1 RCT, RR=0.7 CI 0.4 to 1.1). In terms of global effects, studies reported no differences between risperidone and haloperidol (n=183, RR not much improved 1.0 CI 0.6 to 1.5), and olanzapine and the same control (n=83, RR needing at least one dose of benzodiazepine 0.8 CI 0.5 to 1.1). More people allocated to olanzapine had clinically significant improvement in mental state compared with those given haloperidol (n=83, RR no 'clinically significant improvement' 0.45 CI 0.3 to 0.7, NNH 3 CI 2 to 6). In the risperidone study, however, no such difference was apparent (n=183, RR 'no clinically significant improvement in mental state' 0.85 CI 0.6 to 1.2). Significantly more people given haloperidol (4-16mg) experienced at least one adverse event when compared with risperidone (4-16mg) (n=183, RR 0.9 CI 0.8 to 0.98, NNH 8 CI 4 to 50). Use of anticholinergic medication for extrapyramidal adverse events was less prevalent for people allocated either olanzapine (n=83, RR 0.3 CI 0.2 to 0.7, NNH 4 CI 2 to 14) or risperidone (n=183, RR 0.7 CI 0.5 to 0.9, NNH 4 CI 3 to 9) compared with those given haloperidol. There are no data at all on outcomes such as compliance, cost, social and cognitive functioning, relapse, rehospitalisation, or quality of life. There are no medium to long-term data. Eight ongoing studies may provide more information.

REVIEWER'S CONCLUSIONS

The results of this review are inconclusive. Whether the use of new generation antipsychotics really makes the treatment less off putting and enhances long-term compliance is unclear. Pragmatic, well-designed and reported long-term trials would be useful to answer this question.

Genetic predictors of therapeutic response to clozapine: current status of research

Clozapine is one of the most clinically potent drugs currently available for treating the symptoms of schizophrenia. Compared with conventional antipsychotics it surpasses its predecessors in its ability to treat a wider range of symptoms in otherwise refractory patients, while possessing a low propensity to produce extrapyramidal symptoms. Despite its significant advantages, not all patients benefit from treatment. Some patients react adversely to therapy while others fail to respond adequately. If those most likely to benefit from clozapine could be identified prior to treatment, this would significantly improve the clinical management of these patients. Genetic alterations in drug-metabolising enzymes have previously been demonstrated to influence the efficacy of clinically relevant drugs. It is possible that similar alterations in these and other systems may influence the response variability of patients to clozapine. Pharmacogenetic studies are at present investigating genes encoding drug receptors, drug-metabolising enzymes and neurotransmitter transporters to identify genetic variants that may be important. To date polymorphisms within serotonergic and dopaminergic pathways have been implicated, though the involvement of similar variants in other candidate systems is also likely. This information will ultimately enable the genetic prediction of patients most likely to benefit from the drug, and in the process would alleviate the unnecessary exposure of predisposed individuals to potentially serious adverse effects.

Quetiapine treatment of children with Tourette's syndrome: report of two cases

Two children with Tourette's syndrome and comorbid disorders were treated with quetiapine, an atypical antipsychotic successfully used in patients with psychoses and schizophrenia with low incidence of extrapyramidal side effects. Clinical observations and standardized rating scales suggested that this drug produced beneficial effects on tics and other symptoms. Adverse effects (at low doses) were minimal. Because it was suggested that tic efficacy of the newer antipsychotics was related to higher D2 occupancy (with the exception of quetiapine and clozapine, which have relatively low D2 activity), it is hypothesized that tic patients are D2 sensitive and need lower doses of medications. These children were treated naturalistically and were reported retrospectively because of their encouraging outcomes. However, these findings should be interpreted with caution, because no contrast groups, drug withdrawal, or placebo were utilized. Controlled studies are needed to determine the efficacy of quetiapine in the treatment of Tourette's syndrome.

Antipsychotic drug use in neurodegenerative disease in the elderly: problems and potential from a pharmacological perspective

The past decade has seen the introduction of several new antipsychotics for the treatment of schizophrenia. These drugs demonstrate substantially lower levels of extrapyramidal side effects (EPS) than the classical antipsychotics, as well as having (often poorly supported) claims of increased efficacy at ameliorating certain schizophrenic syndromes. Increasingly, these 'atypical' drugs are being used in the treatment of psychotic or related behavioural disturbances in patients with neurodegenerative disease. Thus, some newer antipsychotics are particularly valuable in ameliorating the L-dopa-induced psychosis in Parkinson's disease, while behavioural problems in dementing disorders, such as those occurring in Alzheimer's disease, are also frequently treated by antipsychotic drugs. The relationship between drug pharmacology and neurotransmitter pathology is essential to understanding the relative efficacy of individual antipsychotic drugs in treating the psychotic and behavioural disturbances of neurodegenerative disorders.

Brain-derived neurotrophic factor and tyrosine kinase receptor TrkB in rat brain are significantly altered after haloperidol and risperidone administration

The antipsychotics haloperidol and risperidone are widely used in the therapy of schizophrenia. The former drug mainly acts on the dopamine (DA) D(2) receptor whereas risperidone binds to both DA and serotonin (5HT) receptors, particularly in the neurons of striatal and limbic structures. Recent evidence suggests that neurotrophins might also be involved in antipsychotic action in the central nervous system (CNS). We have previously reported that haloperidol and risperidone significantly affect brain nerve growth factor (NGF) level suggesting that these drugs influence the turnover of endogenous growth factors. Brain-derived neurotrophic factor (BDNF) supports survival and differentiation of developing and mature brain DA neurons. We hypothesized that treatments with haloperidol or risperidone will affect synthesis/release of brain BDNF and tested this hypothesis by measuring BDNF and TrkB in rat brain regions after a 29-day-treatment with haloperidol or risperidone added to chow. Drug treatments had no effects on weight of brain regions. Chronic administration of these drugs, however, altered BDNF synthesis or release and expression of TrkB-immunoreactivity within the brain. Both haloperidol and risperidone significantly decreased BDNF concentrations in frontal cortex, occipital cortex and hippocampus and decreased or increased TrkB receptors in selected brain structures. Because BDNF can act on a variety of CNS neurons, it is reasonable to hypothesize that alteration of brain level of this neurotrophin could constitute one of the mechanisms of action of antipsychotic drugs. These observations also support the possibility that neurotrophic factors play a role in altered brain function in schizophrenic disorders.

The new antipsychotics--some pharmacological aspects of their problems and potential

The drug treatment of schizophrenia still offers many challenges, despite the efficacy of the classical antipsychotics. Although the more recently introduced drugs demonstrate a diminished incidence of certain side effects, notably extrapyramidal motor symptoms, it is clear that they do not adequately address all symptoms of the disease. In addition, weight gain remains a major problem following treatment with many older and newer antipsychotic drugs. Nevertheless, some progress has been made towards ameliorating negative, depressive and cognitive features of schizophrenia. The newer antipsychotics show differential effects against these and other symptoms and thus their pharmacological profiles provide us with clues as to the receptor mechanisms underlying their therapeutic and side effects.

Discriminative stimulus properties of antipsychotics

Drug discrimination methodology has been used in a number of ways to analyze the actions of novel and putative novel antipsychotics in vivo. Recent studies suggest (a) in contrast to earlier theorizing, antagonism of the low-dose d-amphetamine stimulus in rats may not be an effective screen for novel antipsychotics; (b) dopamine D2-like agonists and antagonists, some of which are putative antipsychotics, can be studied in vivo as discriminative cues, although there is a pressing need for more selective drugs that differentiate the various members of the D2 family. (c) antagonism of the cue induced by the noncompetitive NMDA antagonist MK-801, which has been proposed as a possible screen for clozapine-like compounds, may be an unreliable assay; and (d) the clozapine stimulus is probably a compound cue (a drug "mixture"), which can be used to screen for novel clozapine-like antipsychotics, although the precise receptor mechanisms involved in mediating the clozapine stimulus, and its direct relevance to the antipsychotic action of clozapine remains to be proven conclusively.

Region-specific induction of deltaFosB by repeated administration of typical versus atypical antipsychotic drugs

Whereas acute administration of many types of stimuli induces c-Fos and related proteins in brain, recent work has shown that chronic perturbations cause the region-specific accumulation of novel Fos-like proteins of 35-37 kD. These proteins, termed chronic FRAs (Fos-related antigens), have recently been shown to be isoforms of DeltaFosB, which accumulate in brain due to their enhanced stability. In the present study, we sought to extend earlier findings that documented the effects of acute administration of antipsychotic drugs (APDs) on induction of Fos-like proteins by investigating the ability of typical and aytpical APDs, after chronic administration, to induce these DeltaFosB isoforms in several brain regions implicated in the clinical actions of these agents. By Western blotting we found that chronic administration of the typical APD, haloperidol, dramatically induces DeltaFosB in caudate-putamen (CP), a brain region associated with the extrapyramidal side effects of this drug. A smaller induction was seen in the nucleus accumbens (NAc) and prefrontal cortex (PFC), brain regions associated with the antipsychotic effects of the drug. In contrast, chronic administration of the prototype atypical APD clozapine failed to significantly increase levels of DeltaFosB in any of the three brain regions, and even tended to reduce DeltaFosB levels in the NAc. Two putative atypical APDs, risperidone and olanzapine, produced small but still significant increases in the levels of DeltaFosB in CP, but not NAc or PFC. Studies with selective receptor antagonists suggested that induction of DeltaFosB in CP and NAc is most dependent on antagonism of D2-D3 dopamine receptors, with antagonism of D1-like receptors most involved in the PFC. Immunohistochemical analysis confirmed the greater induction of DeltaFosB in CP by typical versus atypical APDs, with no significant induction seen in PFC with either class of APD. Together, these findings demonstrate that repeated administration of APDs results in the induction of long-lasting Fos-like transcription factors that could mediate some of the persistent and region-specific changes in brain function associated with chronic drug exposure. Synapse 33:118-128, 1999.

Psychosis and medication: strategies for improving adherence

The development of traditional anti-psychotic medication has led to improvements in the care of mentally ill people. These medications have been the mainstay of drug treatment for schizophrenia for many years. In recent years, however, the advent of so-called 'atypical' anti-psychotics has enabled patients to be treated without experiencing the range of severe side-effects associated with traditional medicines. Ensuring mentally ill patients take prescribed treatment is seen as an important element of the work of mental health nurses. Adopting approaches which are non-adversarial may provide better outcomes than straightforward advice giving. A combination of psycho-education and a technique known as brief motivational interviewing could provide a useful starting point for nurses. Whether such approaches will be supported given recent declarations on policy intentions remains to be seen.

Efficacy and extrapyramidal side-effects of the new antipsychotics olanzapine, quetiapine, risperidone, and sertindole compared to conventional antipsychotics and placebo. A meta-analysis of randomized controlled trials

The objective of this meta-analysis is to summarize the efficacy and tolerability of the new antipsychotics risperidone, olanzapine, sertindole and quetiapine in schizophrenia compared to placebo and conventional antipsychotics. The main results are: (1) All of the 4 new drugs are more effective than placebo, but the magnitude of the effect is only moderate [mean effect size, r, of all antipsychotics vs. placebo = 0.25, with a 95% confidence interval (CI) = 0.22-0.28, n = 2477]. (2) According to the studies published to date, sertindole and quetiapine are as effective as haloperidol, and risperidone and olanzapine are slightly more effective than haloperidol in the treatment of global schizophrenic symptomatology. (3) With respect to negative symptoms, all new antipsychotics are more effective than placebo. However, contrary to widespread opinion, so is the 'conventional' antipsychotic haloperidol. Risperidone and olanzapine are slightly superior, sertindole is as effective and--according to the only study fully published to date--quetiapine is even slightly less effective than haloperidol in this regard. (4) All new antipsychotics are associated with less frequent use of antiparkinson medication than haloperidol, with risperidone appearing to have a slightly less favourable EPS-profile than the other new antipsychotics. The methodological limitations of this review, the generalizability of the results and expectations from future research are discussed.