Dopamine D2 receptor occupancy in vivo by the novel atypical antipsychotic olanzapine--a 123I IBZM single photon emission tomography (SPET) study

Haloperidol (oral) versus olanzapine (oral) for people with schizophrenia and schizophrenia-spectrum disorders

BACKGROUND

Schizophrenia is often a severe and disabling psychiatric disorder. Antipsychotics remain the mainstay of psychotropic treatment for people with psychosis. In limited resource and humanitarian contexts, it is key to have several options for beneficial, low-cost antipsychotics, which require minimal monitoring. We wanted to compare oral haloperidol, as one of the most available antipsychotics in these settings, with a second-generation antipsychotic, olanzapine.

OBJECTIVES

To assess the clinical benefits and harms of haloperidol compared to olanzapine for people with schizophrenia and schizophrenia-spectrum disorders.

SEARCH METHODS

We searched the Cochrane Schizophrenia study-based register of trials, which is based on monthly searches of CENTRAL, CINAHL, ClinicalTrials.gov, Embase, ISRCTN, MEDLINE, PsycINFO, PubMed and WHO ICTRP. We screened the references of all included studies. We contacted relevant authors of trials for additional information where clarification was required or where data were incomplete. The register was last searched on 14 January 2023.

SELECTION CRITERIA

Randomised clinical trials comparing haloperidol with olanzapine for people with schizophrenia and schizophrenia-spectrum disorders. Our main outcomes of interest were clinically important change in global state, relapse, clinically important change in mental state, extrapyramidal side effects, weight increase, clinically important change in quality of life and leaving the study early due to adverse effects.

DATA COLLECTION AND ANALYSIS

We independently evaluated and extracted data. For dichotomous outcomes, we calculated risk ratios (RR) and their 95% confidence intervals (CI) and the number needed to treat for an additional beneficial or harmful outcome (NNTB or NNTH) with 95% CI. For continuous data, we estimated mean differences (MD) or standardised mean differences (SMD) with 95% CIs. For all included studies, we assessed risk of bias (RoB 1) and we used the GRADE approach to create a summary of findings table.

MAIN RESULTS

We included 68 studies randomising 9132 participants. We are very uncertain whether there is a difference between haloperidol and olanzapine in clinically important change in global state (RR 0.84, 95% CI 0.69 to 1.02; 6 studies, 3078 participants; very low-certainty evidence). We are very uncertain whether there is a difference between haloperidol and olanzapine in relapse (RR 1.42, 95% CI 1.00 to 2.02; 7 studies, 1499 participants; very low-certainty evidence). Haloperidol may reduce the incidence of clinically important change in overall mental state compared to olanzapine (RR 0.70, 95% CI 0.60 to 0.81; 13 studies, 1210 participants; low-certainty evidence). For every eight people treated with haloperidol instead of olanzapine, one fewer person would experience this improvement. The evidence suggests that haloperidol may result in a large increase in extrapyramidal side effects compared to olanzapine (RR 3.38, 95% CI 2.28 to 5.02; 14 studies, 3290 participants; low-certainty evidence). For every three people treated with haloperidol instead of olanzapine, one additional person would experience extrapyramidal side effects. For weight gain, the evidence suggests that there may be a large reduction in the risk with haloperidol compared to olanzapine (RR 0.47, 95% CI 0.35 to 0.61; 18 studies, 4302 participants; low-certainty evidence). For every 10 people treated with haloperidol instead of olanzapine, one fewer person would experience weight increase. A single study suggests that haloperidol may reduce the incidence of clinically important change in quality of life compared to olanzapine (RR 0.72, 95% CI 0.57 to 0.91; 828 participants; low-certainty evidence). For every nine people treated with haloperidol instead of olanzapine, one fewer person would experience clinically important improvement in quality of life. Haloperidol may result in an increase in the incidence of leaving the study early due to adverse effects compared to olanzapine (RR 1.99, 95% CI 1.60 to 2.47; 21 studies, 5047 participants; low-certainty evidence). For every 22 people treated with haloperidol instead of olanzapine, one fewer person would experience this outcome. Thirty otherwise relevant studies and several endpoints from 14 included studies could not be evaluated due to inconsistencies and poor transparency of several parameters. Furthermore, even within studies that were included, it was often not possible to use data for the same reasons. Risk of bias differed substantially for different outcomes and the certainty of the evidence ranged from very low to low. The most common risks of bias leading to downgrading of the evidence were blinding (performance bias) and selective reporting (reporting bias).

AUTHORS' CONCLUSIONS

Overall, the certainty of the evidence was low to very low for the main outcomes in this review, making it difficult to draw reliable conclusions. We are very uncertain whether there is a difference between haloperidol and olanzapine in terms of clinically important global state and relapse. Olanzapine may result in a slightly greater overall clinically important change in mental state and in a clinically important change in quality of life. Different side effect profiles were noted: haloperidol may result in a large increase in extrapyramidal side effects and olanzapine in a large increase in weight gain. The drug of choice needs to take into account side effect profiles and the preferences of the individual. These findings and the recent inclusion of olanzapine alongside haloperidol in the WHO Model List of Essential Medicines should increase the likelihood of it becoming more easily available in low- and middle- income countries, thereby improving choice and providing a greater ability to respond to side effects for people with lived experience of schizophrenia. There is a need for additional research using appropriate and equivalent dosages of these drugs. Some of this research needs to be done in low- and middle-income settings and should actively seek to account for factors relevant to these. Research on antipsychotics needs to be person-centred and prioritise factors that are of interest to people with lived experience of schizophrenia.

IBZM-SPECT imaging of dopamine D2 receptors with typical and atypical antipsychotics

Considerable progress has been achieved over the past 15 years in uncovering the biological basis of major psychiatric disorders. Since psychopharmacological treatment is thought tc act on the underlying biological basis of the disease, brain imaging techniques enable us to understand the mechanism of action of such compounds. One important tool used to determine patterns of brain dysfunction and how psychopharmacological agents such as antipsychotic compounds work is single-photon emission computerised tomography (SPECT). This technique allows determination of striatal D2 receptor occupancy rates, which are associated with the extrapyramidal side effects (EPS) of antipsychotic drugs. Studies have confirmed that atypical antipsychotic agents have lower occupancy rates than typical agents. No association has been found between D2 receptor occupancy rates n the striatum and antipsychotic efficacy, and it therefore appears that striatal D2 receptor occupancy rates are not necessary for the antipsychotic effect of such agents in schizophrenia. The availability of more refined radioligands will help us not only to understand the action of antipsychotics but also the pathophysiology of schizophrenia.

Olanzapine in practice: a prospective naturalistic study

Aims and method

The study aimed to evaluate the effectiveness of the naturalistic use of olanzapine. Prescribers of olanzapine were asked to provide baseline and six-week Brief Psychiatric Rating Scale scores for 56 in-patients. Withdrawals from treatment were also noted.

Results

Olanzapine was not effective in any of the 12 patients with refractory schizophrenia and four patients worsened. In 36 patients with non-refractory schizophrenia, 16 (44%) improved and 10 (28%) were categorised as treatment failures. of eight patients with non-schizophrenic psychosis, only one improved and two were treatment failures.

Clinical implications

Olanzapine is effective in treating non-refractory schizophrenia, but appears to have no beneficial effect in refractory schizophrenia.

Practitioner Review: The effects of atypical antipsychotics and mood stabilisers in the treatment of depressive symptoms in paediatric bipolar disorder

BACKGROUND

The management of depressive and mixed symptoms in children and adolescents with bipolar disorder (BD) remains a matter of debate. The goal of this review is, thus, to systematically examine the impact of atypical antipsychotics (AAPs) and mood stabilisers in the treatment of bipolar depression and/or mixed states.

METHODS

A literature search was conducted for studies assessing the efficacy of pharmacological treatments for bipolar disorder type I, type II and not otherwise specified with a recent depressive, mixed or manic episode (with depressive symptoms) following DSM-IV criteria in children and adolescents as either acute or maintenance treatment. The databases searched were PubMed/Medline, Google Scholar and Tripdatabase, as well as ClinicalTrials.gov. The search was limited to clinical trials, systematic reviews, meta-analyses and open-label trials published in the English language between the years 2000 and 2015. Sixty clinical studies were found assessing the efficacy of mood stabilisers and AAPs in paediatric BD. Fifteen studies were not included in the primary analysis because they did not assess depressive symptomology/include scores on rating scales of depressive symptoms (Online Supplementary Material).

RESULTS

There is sufficient evidence for a Grade A recommendation of the use of olanzapine plus fluoxetine at reducing depressive symptoms in bipolar depression and of quetiapine at high doses for depressive symptoms occurring during mixed episodes. Importantly, even though monotherapy with aripiprazole, risperidone, valproate and lithium was effective at controlling mania, these drugs were not effective at reducing depressive symptoms (level A evidence for nonrecommendation).

CONCLUSIONS

These results mostly overlap with the approved treatments for bipolar depression in adults.

Classics in Chemical Neuroscience: Aripiprazole

Aripiprazole was the first antipsychotic developed to possess agonist properties at dopamine D₂ autoreceptors, a groundbreaking strategy that presented a new vista for schizophrenia drug discovery. The dopamine D₂ receptor is the crucial target of all extant antipsychotics, and all developed prior to aripiprazole were D₂ receptor antagonists. Extensive blockade of these receptors, however, typically produces extrapyramidal (movement) side effects, which plagued first-generation antipsychotics, such as haloperidol. Second-generation antipsychotics, such as clozapine, with unique polypharmacology and D₂ receptor binding kinetics, have significantly lower risk of movement side effects but can cause myriad additional ones, such as severe weight gain and metabolic dysfunction. Aripiprazole's polypharmacology, characterized by its unique agonist activity at dopamine D₂ and D₃ and serotonin 5-HT_1A receptors, as well as antagonist activity at serotonin 5-HT_2A receptors, translates to successful reduction of positive, negative, and cognitive symptoms of schizophrenia, while also mitigating risk of weight gain and movement side effects. New observations, however, link aripiprazole to compulsive behaviors in a small group of patients, an unusual side effect for antipsychotics. In this review, we discuss the chemical synthesis, pharmacology, pharmacogenomics, drug metabolism, and adverse events of aripiprazole, and we present a current understanding of aripiprazole's neurotherapeutic mechanisms, as well as the history and importance of aripiprazole to neuroscience.

Receptor targets for antidepressant therapy in bipolar disorder: an overview

The treatment of bipolar depression is one of the most challenging issues in contemporary psychiatry. Currently only quetiapine and the olanzapine-fluoxetine combination are officially approved by the FDA against this condition. The neurobiology of bipolar depression and the possible targets of bipolar antidepressant therapy remain relatively elusive. We performed a complete and systematic review to identify agents with definite positive or negative results concerning efficacy followed by a second systematic review to identify the pharmacodynamic properties of these agents. The comparison of properties suggests that the stronger predictors for antidepressant efficacy in bipolar depression were norepinephrine alpha-1, dopamine D1 and histamine antagonism, followed by 5-HT2A, muscarinic and dopamine D2 and D3 antagonism and eventually by norepinephrine reuptake inhibition and 5HT-1A agonism. Serotonin reuptake which constitutes the cornerstone in unipolar depression treatment does not seem to play a significant role for bipolar depression. Our exhaustive review is compatible with a complex model with multiple levels of interaction between the major neurotransmitter systems without a single target being either necessary or sufficient to elicit the antidepressant effect in bipolar depression.

The psychopharmacology of aggressive behavior: a translational approach: part 2: clinical studies using atypical antipsychotics, anticonvulsants, and lithium

Patients experiencing mental disorders are at an elevated risk for developing aggressive behavior. In the past 10 years, the psychopharmacological treatment of aggression has changed dramatically owing to the introduction of atypical antipsychotics on the market and the increased use of anticonvulsants and lithium in the treatment of aggressive patients.This review (second of 2 parts) uses a translational medicine approach to examine the neurobiology of aggression, discussing the major neurotransmitter systems implicated in its pathogenesis (serotonin, glutamate, norepinephrine, dopamine, and γ-aminobutyric acid) and the neuropharmacological rationale for using atypical antipsychotics, anticonvulsants, and lithium in the therapeutics of aggressive behavior. A critical review of all clinical trials using atypical antipsychotics (aripiprazole, clozapine, loxapine, olanzapine, quetiapine, risperidone, ziprasidone, and amisulpride), anticonvulsants (topiramate, valproate, lamotrigine, and gabapentin), and lithium are presented. Given the complex, multifaceted nature of aggression, a multifunctional combined therapy, targeting different receptors, seems to be the best strategy for treating aggressive behavior. This therapeutic strategy is supported by translational studies and a few human studies, even if additional randomized, double-blind, clinical trials are needed to confirm the clinical efficacy of this framework.

Antipsychotic drug treatment for elderly people with late-onset schizophrenia

BACKGROUND

Schizophrenia is usually considered an illness of young adulthood. However, onset after the age of 40 years is reported in 23% of patients hospitalised with schizophrenia. At least 0.1% of the world's elderly population have a diagnosis of late-onset schizophrenia which seems to differ from earlier onset schizophrenia on a variety of counts including response to antipsychotic drugs.

OBJECTIVES

To assess the effects of antipsychotic drugs for elderly people with late-onset schizophrenia.

SEARCH METHODS

We searched the Cochrane Schizophrenia Group Trials Register (January 2010) which is based on regular searches of CINAHL, EMBASE, MEDLINE and PsycINFO. We inspected references of all identified studies for further trials. We contacted relevant authors of trials for additional information.

SELECTION CRITERIA

All relevant randomised controlled trials that compared antipsychotic drugs with other treatments for elderly people (at least 80% older than 65 years) with a recent (within five years) diagnosis of schizophrenia or schizophrenia like illnesses.

DATA COLLECTION AND ANALYSIS

For the 2010 search, two new review authors (AE, AG) inspected all citations to ensure reliable selection. We assessed methodological quality of trials using the criteria recommended in the Cochrane Handbook for Systematic Reviews of Interventions. AE and AG also independently extracted data. For homogenous dichotomous data, we planned to calculate the relative risk (RR) and 95% confidence interval (CI).

MAIN RESULTS

There were no included studies in the original version of this review (2002 search). The 2010 search for the current update produced 211 references, among which we identified 88 studies. Only one study met the inclusion criteria and was of acceptable quality. This was an eight-week randomised trial of risperidone and olanzapine in 44 inpatients with late-onset schizophrenia. All participants completed the eight-week trial, indicating that both drugs were well tolerated. Unfortunately, this study provided little usable data. We excluded a total of 81 studies, 77 studies because they either studied interventions other than antipsychotic medication or because they involved elderly people with chronic - not late-onset - schizophrenia. We excluded a further four trials of antipsychotics in late-onset schizophrenia because of flawed design. Five studies are still awaiting classification, and one is on-going.

AUTHORS' CONCLUSIONS

There is no trial-based evidence upon which to base guidelines for the treatment of late-onset schizophrenia. There is a need for good quality-controlled clinical trials into the effects of antipsychotics for this group. Such trials are possible. Until they are undertaken, people with late-onset schizophrenia will be treated by doctors using clinical judgement and habit to guide prescribing.

Within-subject comparison of striatal D2 receptor occupancy measurements using [123I]IBZM SPECT and [11C]Raclopride PET

Antipsychotic-induced D2 receptor occupancy values tend to be lower when measured with [(123)I]IBZM SPECT than with [(11)C]Raclopride PET. To clarify this issue, D2 receptor occupancy was measured in the same subjects using both techniques. Twenty patients with schizophrenia on monotherapy with risperidone (n=7; 3-9 mg/d), olanzapine (n=5; 5-20 mg/d) or clozapine (n=8; 150-450 mg/d) at stable doses, and ten healthy volunteers (HV) underwent both a [(123)I]IBZM SPECT and a [(11)C]Raclopride PET examinations in random order on different days within a week. Patients with schizophrenia were scanned at a fixed interval after last dose administration. Quantification of receptor availability was performed using the most conventional methods from the literature: the tissue ratio derived specific uptake ratios (SUR) were used for SPECT, and simplified reference tissue model (SRTM) derived binding potentials (BP(ND)) for PET. Analysis was performed using both occipital cortex and cerebellum as reference regions for both modalities. Striatal D2 receptor occupancy was measured as the percentage reduction of [(123)I]IBZM SUR or [(11)C]Raclopride BP(ND) compared to the population average measured in HV using the same modality. Occupancy values measured by SPECT were lower than those measured with PET, by 12.4% and 13.8% when occipital cortex and cerebellum were used as reference regions. This difference should be taken in consideration when interpreting reported antipsychotic striatal D2 receptor occupancy values from the literature.

Upcoming agents for the treatment of schizophrenia: mechanism of action, efficacy and tolerability

Since the introduction of a group of atypical antipsychotics in the 1990s, there has been a decline in the rate of new antipsychotics being introduced into clinical practice. However, with increasing safety and efficacy concerns over currently available drugs and a dearth of options available for atypical depot formulations, there is a considerable need for the development of new formulations and agents. This review examines the profile of seven antipsychotic drugs currently in the premarketing stage of development and summarizes their mechanism of action, clinical potential and safety.Asenapine is an antipsychotic with activity for multiple receptors and has potential to improve negative and cognitive symptoms of schizophrenia. Bifeprunox is a partial dopamine D2 and serotonin 5-HT(1A) receptor agonist showing a less than convincing efficacy profile, but which may offer safety advantages over available agents by means of a reduced risk of metabolic complications. Iloperidone is a D2 and 5-HT(2A) receptor antagonist requiring further studies to establish its effectiveness. It has a high affinity for alpha(1)-adrenoceptors, which can lead to associated haemodynamic adverse effects. Nemonapride is essentially a typical antipsychotic drug, similar in structure to sulpiride, which has been available for some time in Japan. It has efficacy against positive symptoms and has shown some antidepressant and anxiolytic properties, although efficacy data for it are somewhat limited. Norclozapine (N-desmethylclozapine) is a major metabolite of clozapine formed by its demethylation. Its partial agonist activity at D2 receptors has raised interest in it as an antipsychotic in its own right. In addition, it appears to have muscarinic agonist activity, which is believed to be responsible for the observed positive effects it has on cognition. It was envisaged to be effective as an adjunct to other agents or at high doses in the treatment of refractory schizophrenia, although a recent randomized, controlled study showed that it was no more effective than placebo in patients with schizophrenia experiencing an acute psychotic episode. Olanzapine pamoate depot injection has shown comparable efficacy to oral olanzapine in several studies. However, it has provoked considerable safety concerns by its association with inadvertent intravascular injection events in numerous patients. This accidental intravascular administration of olanzapine pamoate leads to excessive sedation, confusion, dizziness and altered speech. Post-injection observation periods and postmarketing surveillance are planned following the introduction of the depot. Paliperidone palmitate is the palmitate ester of paliperidone, the major metabolite of risperidone, and is formulated as a long-acting injection for intramuscular use. Its pharmacology is comparable to risperidone, having D2 and 5-HT(2A) receptor antagonist activity. Efficacy studies have shown positive results, and because paliperidone has no antagonistic activity at cholinergic receptors, it has low potential for anticholinergic adverse effects, including cognitive dysfunction. However, with higher doses, the frequency of extrapyramidal side effects and orthostatic hypotension have been shown to be greater than with placebo.

Pharmacokinetics and time-course of D(2) receptor occupancy induced by atypical antipsychotics in stabilized schizophrenic patients

The (123)I-IBZM SPECT measured D(2) receptor occupancy (D(2)RO) in chronically dosed, stabilized schizophrenic patients and its relationship with antipsychotic (AP) pharmacokinetics (PK) over time is still unclear. The aims of this study were: 1) To define the relationship between striatal D(2) receptor occupancy (D( 2)RO) and plasma concentration (C(P)) in stabilized schizophrenic patients on clinically relevant doses using (123)I-IBZM SPECT; 2) To investigate the time course of AP-induced D(2)RO and corresponding C(P). Forty-six schizophrenic patients on their clinically required doses of risperidone, olanzapine, clozapine or quetiapine were included. D( 2)RO and C(P) were measured over time following a sparse-sampling experimental design, and individual PK and D(2)RO-time profiles were estimated using a population approach. Observed striatal D(2)RO and C(P) ranges were 28-75% and 9.4-60.5 ng/mL for risperidone, 22-84% and 8.6-89.5 ng/mL for olanzapine, 5-53% and 41.6-818.2 ng/mL for clozapine and 0-64% and 37.9-719.6 ng/mL for quetiapine. A PK-D(2)RO relationship was found for the four APs. D(2)RO pattern over time was stable for risperidone, olanzapine and clozapine but fluctuating for quetiapine. Stabilized schizophrenic patients show a wide range of both D(2)RO and C(P) at clinically effective doses of the four AP, suggesting that clinical response to these AP may be maintained with D(2)RO below 65%. D(2)RO patterns over time differ between AP. These results should be considered for accurate interpretation of D(2)RO measurements, proper design of studies and optimization of drug regimens for patients on AP treatment.

Striatal D(2) receptor occupancy in bipolar patients treated with olanzapine

We explored the relationship between striatal dopamine-2 (D(2)) receptor occupancy and extra-pyramidal symptoms (EPS) in bipolar patients receiving olanzapine. Seventeen patients with a DSM-IV diagnosis of bipolar disorder were treated with 5-45 mg/day olanzapine for at least 14 days. After that period, D(2) receptor occupancy was determined using Iodobenzamide (IBZM) and SPECT. EPS were assessed by the Simpson-Angus Scale (SAS) and Barnes-Akathisia Scale (BAS). We found a dose-dependent increase in occupancy: 5 mg led to 28-50%, 10 mg to 40-68%, 15 mg to 69%, 20 mg to 57-66%, 30 mg to 66% and 45 mg to 80% D(2) receptor occupancy; and a significant correlation between plasma levels and occupancy (R(2)=.55, P=.001). Similar to schizophrenic patients, bipolar patients did not exhibit EPS at D(2) occupancy levels of 28 to 80%. Although we did not find an increased vulnerability for acute EPS in bipolar patients receiving olanzapine at clinical relevant doses, this needs to be replicated with larger sample sizes.

Gender differences in prolactin elevation induced by olanzapine in Japanese drug-naïve schizophrenic patients

We investigated the effect of gender on plasma prolactin levels in 20 Japanese drug-naïve schizophrenic patients [10 male, 10 female, aged 25.4+/-10.3 (mean+/-S.D.), range = 12-46 years] treated with olanzapine. Plasma prolactin levels were measured at baseline, and weeks 3 and 8 after starting titration of olanzapine. Comparisons of plasma prolactin levels between baseline and week 3, and between baseline and week 8 were made by repeated analysis of variance (ANOVA) and paired t-test. Two-way ANOVA showed a significant difference in olanzapine-induced prolactin changes between male and female patients (P = 0.037). In male patients (n = 10), the plasma concentration of prolactin at week 3 was significantly higher than at baseline (P = 0.016), but there was no significant difference between the plasma concentration of prolactin at week 8 and at baseline or week 3 (P = 0.191). In female patients (n = 10), there was a significant change of prolactin between baseline and week 3 (P = 0.005), and between baseline and week 8 (P = 0.047). Our results indicate the possibility of gender differences in prolactin elevation induced by olanzapine in Japanese drug-naïve schizophrenic patients. These gender-based findings may be helpful for clinicians when deciding the frequency of follow-up visits once a patient starts olanzapine therapy.

Occupancy of striatal and extrastriatal dopamine D2/D3 receptors by olanzapine and haloperidol

There have been conflicting reports as to whether olanzapine produces lower occupancy of striatal dopamine D(2)/D(3) receptor than typical antipsychotic drugs and preferential occupancy of extrastriatal dopamine D(2)/D(3) receptors. We performed [(18)F] fallypride PET studies in six schizophrenic subjects treated with olanzapine and six schizophrenic subjects treated with haloperidol to examine the occupancy of striatal and extrastriatal dopamine receptors by these antipsychotic drugs. [(18)F] setoperone PET studies were performed in seven olanzapine-treated subjects to determine 5-HT(2A) receptor occupancy. Occupancy of dopamine D(2)/D(3) receptors by olanzapine was not significantly different from that seen with haloperidol in the putamen, ventral striatum, medial thalamus, amygdala, or temporal cortex, that is, 67.5-78.2% occupancy; olanzapine produced no preferential occupancy of dopamine D(2)/D(3) receptors in the ventral striatum, medial thalamus, amygdala, or temporal cortex. There was, however, significantly lower occupancy of substantia nigra/VTA dopamine D(2)/D(3) receptors in olanzapine-treated compared to haloperidol-treated subjects, that is, 40.2 vs 59.3% (p=0.0014, corrected for multiple comparisons); in olanzapine-treated subjects, the substantia nigra/VTA was the only region with significantly lower dopamine D(2)/D(3) receptor occupancy than the putamen, that is, 40.2 vs 69.2% (p<0.001, corrected for multiple comparison). Occupancy of 5-HT(2A) receptors was 85-93% in the olanzapine- treated subjects. The results of this study demonstrated that olanzapine does not produce preferential occupancy of extrastriatal dopamine D(2)/D(3) receptors but does spare substantia nigra/VTA receptors. Sparing of substantia nigra/VTA dopamine D(2)/D(3) receptor occupancy may contribute to the low incidence of extrapyramidal side effects in olanzapine-treated patients.

Treatment response to olanzapine and haloperidol and its association with dopamine D receptor occupancy in first-episode psychosis

OBJECTIVE

Response to typical antipsychotic medication has been associated with achieving a level of striatal dopamine D2 receptor occupancy in the range of 65% to 70%. We undertook this study to determine whether response to the atypical antipsychotic olanzapine occurs at lower levels of D2 receptor occupancy.

METHOD

Eighteen patients who presented with a first episode of psychosis were randomized to receive olanzapine 5 mg daily or haloperidol 2 mg daily in a double-blind design. We acquired positron emission tomography (PET) scans using the D2 ligand [11C]raclopride within the first 15 days of treatment to determine the percentage of D2 receptors occupied by the medication. According to response, dosage was then adjusted to a maximum dosage of 20 mg daily of either drug. PET scans were repeated after 10 to 12 weeks of treatment.

RESULTS

At the first PET scan, the 8 olanzapine-treated patients had significantly lower D2 receptor occupancies (mean 63.4%, SD 7.3) than those observed in the 10 patients treated with haloperidol (mean 73.0%, SD 6.1). When patients were rescanned following dosage adjustment, mean D2 receptor occupancies were greater than 70% in both groups. D2 receptor occupancies did not differ significantly between the olanzapine-treated group (mean 72.0%, SD 5.7) and the haloperidol-treated group (mean 78.7%, SD 7.6).

CONCLUSIONS

These results suggest that, in patients being treated for a first episode of psychosis, olanzapine has its antipsychotic effect at approximately the same levels of D2 receptor occupancy as are achieved with low dosages of haloperidol.

Quetiapine (Seroquel) shows a pattern of behavioral effects similar to the atypical antipsychotics clozapine and olanzapine: studies with tremulous jaw movements in rats

RATIONALE

Previous studies demonstrated that clozapine and olanzapine suppressed tacrine-induced jaw movements at lower doses than those required for suppression of lever pressing.

OBJECTIVE

The present studies were undertaken to evaluate the novel atypical antipsychotic quetiapine using the jaw movement model.

METHODS

The effect of acute quetiapine on the suppression of tacrine-induced tremulous jaw movements was examined. To determine the relative potency of this effect compared with other behavioral effects of quetiapine, suppression of lever pressing also was studied. In other studies, rats received quetiapine for 14 consecutive days to study the effects of repeated injections of this drug.

RESULTS

Acute quetiapine injections decreased tacrine-induced jaw movements and lever pressing. The ratio of the ED50 for suppression of jaw movements divided by the ED50 for suppression of lever pressing was used as an index of liability to produce motor side effects, and the present results demonstrate that quetiapine has a ratio similar to that previously shown for clozapine and olanzapine. In the repeated-administration studies, quetiapine failed to induce jaw movements. On day 14, quetiapine reduced tacrine-induced tremulous jaw movements, and in a parallel experiment quetiapine significantly suppressed lever pressing on days 1-14. Repeated injections of quetiapine reduced tacrine-induced jaw movements over a dose range lower than that required for suppression of lever pressing.

CONCLUSIONS

On tests of jaw movement activity and lever pressing after both acute and repeated drug administration, quetiapine showed a profile somewhat similar to clozapine and olanzapine. A theoretical model is offered suggesting that atypical antipsychotics that act on 5-HT or muscarinic receptors have intrinsic antiparkinsonian actions that work in opposition to the motor effects produced by dopamine antagonism.

Olanzapine for schizophrenia

BACKGROUND

Olanzapine is an atypical antipsychotic reported to be effective without producing disabling extrapyramidal adverse effects associated with older, typical antipsychotic drugs.

OBJECTIVES

To determine the clinical effects and safety of olanzapine compared with placebo, typical and other atypical antipsychotic drugs for schizophrenia and schizophreniform psychoses.

SEARCH STRATEGY

We updated the first search [Biological Abstracts (1980-1999), The Cochrane Library (Issue 2, 1999), EMBASE (1980-1999), MEDLINE (1966-1999), PsycLIT (1974-1999) and The Cochrane Schizophrenia Group's Register (October 2000)] in October 2004 using the Cochrane Schizophrenia's Group's register of trials. We also searched references of all included studies for further trials, and contacted relevant pharmaceutical companies and authors.

SELECTION CRITERIA

We included all randomised clinical trials comparing olanzapine with placebo or any antipsychotic treatment for people with schizophrenia or schizophreniform psychoses.

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

Fifty five trials are included (total n>10000 people with schizophrenia). Attrition from olanzapine versus placebo studies was >50% by six weeks, leaving interpretation of results problematic. Olanzapine appeared superior to placebo at six weeks for the outcome of 'no important clinical response' (any dose, 2 RCTs n=418, RR 0.88 CI 0.8 to 0.1, NNT 8 CI 5 to 27). Although dizziness and dry mouth were reported more frequently in the olanzapine-treated group, this did not reach statistical significance. The olanzapine group gained more weight. When compared with typical antipsychotic drugs, data from several small trials are incomplete. With high attrition in both groups (14 RCTs, n=3344, 38% attrition by six weeks, RR 0.81 CI 0.65 to 1.02) the assumptions included in all data are considerable. For the short term outcome of 'no important clinical response', olanzapine seems as effective as typical antipsychotics (4 RCTs, n=2778, RR 0.90 CI 0.76 to 1.06). People allocated olanzapine experienced fewer extrapyramidal adverse effects than those given typical antipsychotics. Weight change data for the short term are not statistically significant but results between three to 12 months suggest a clinically important average gain of four kilograms for people given olanzapine (4 RCTs, n=186, WMD 4.62, CI 0.6 to 8.64). Twenty three percent of people in trials of olanzapine and other atypical drugs left by eight weeks; 48% by three to12 months (11 RCTs, n=1847, RR 0.91 CI 0.82 to 1.00). There is little to choose between the atypicals, although olanzapine may cause fewer extrapyramidal adverse effects than other drugs in this category. Olanzapine produces more weight gain than other atypicals with some differences reaching conventional levels of statistical significance (1 RCT, n=980, RR gain at 2 years 1.73 CI 1.49 to 2.00, NNH 5 CI 4 to 7). There are very few data for people with first episode illness (1 RCT, duration 6 weeks, n=42). For people with treatment-resistant illness there were no clear differences between olanzapine and clozapine (4 RCTs, n=457).

AUTHORS' CONCLUSIONS

The large proportion of participants leaving studies early in these trials makes it difficult to draw firm conclusions on olanzapine's clinical effects. For people with schizophrenia it may offer antipsychotic efficacy with fewer extrapyramidal adverse effects than typical drugs, but more weight gain. There is a need for further large, long-term randomised trials with more comprehensive data.

Antipsychotic-induced hyperprolactinaemia: mechanisms, clinical features and management

Hyperprolactinaemia is an important but neglected adverse effect of antipsychotic medication. It occurs frequently with conventional antipsychotics and some atypical antipsychotics (risperidone and amisulpride) but is rare with other atypical antipsychotics (aripiprazole, clozapine, olanzapine, quetiapine, ziprasidone). For this reason the terms 'prolactin-sparing' and 'prolactin-raising' are more useful than 'atypical' and 'conventional' when considering the effect of antipsychotic drugs on serum prolactin. During antipsychotic treatment prolactin levels can rise 10-fold or more above pretreatment values. In a recent study approximately 60% of women and 40% of men treated with a prolactin-raising antipsychotic had a prolactin level above the upper limit of the normal range. The distinction between asymptomatic and symptomatic hyperprolactinaemia is important but is often not made in the literature. Some symptoms of hyperprolactinaemia result from a direct effect of prolactin on target tissues but others result from hypogonadism caused by prolactin disrupting the normal functioning of the hypothalamic-pituitary-gonadal axis. Symptoms of hyperprolactinaemia include gynaecomastia, galactorrhoea, sexual dysfunction, infertility, oligomenorrhoea and amenorrhoea. These symptoms are little researched in psychiatric patients. Existing data suggest that they are common but that clinicians underestimate their prevalence. For example, well conducted studies of women treated with conventional antipsychotics have reported prevalence rates of approximately 45% for oligomenorrhoea/amenorrhoea and 19% for galactorrhoea. An illness-related under-function of the hypothalamic-pituitary-gonadal axis in female patients with schizophrenia may also contribute to menstrual irregularities. Long-term consequences of antipsychotic-related hypogonadism require further research but are likely and include premature bone loss in men and women. There are conflicting data on whether hyperprolactinaemia is associated with an increased risk of breast cancer in women. In patients prescribed antipsychotics who have biochemically confirmed hyperprolactinaemia it is important to exclude other causes of prolactin elevation, in particular tumours in the hypothalamic-pituitary area. If a patient has been amenorrhoeic for 1 year or more, investigations should include bone mineral density measurements. Management should be tailored to the individual patient. Options include reducing the dose of the antipsychotic, switching to a prolactin-sparing agent, prescribing a dopamine receptor agonist and prescribing estrogen replacement in hypoestrogenic female patients. The efficacy and risks of the last two treatment options have not been systematically examined. Antipsychotic-induced hyperprolactinaemia should become a focus of interest in the drug treatment of psychiatric patients, particularly given the recent introduction of prolactin-sparing antipsychotics. Appropriate investigations and effective management should reduce the burden of adverse effects and prevent long-term consequences.

Occupancy of dopamine D2 receptors by the atypical antipsychotic drugs risperidone and olanzapine: theoretical implications

RATIONALE

To examine the D2 occupancy of two commonly used antipsychotic medications and relate this to the D2 occupancy by endogenous dopamine in schizophrenia.

OBJECTIVES

The aim of this study is to compare the occupancy of striatal D2 receptors by the atypical antipsychotic medications risperidone and olanzapine at fixed dosages and to estimate the effect on D2 occupancy by dopamine as a result of these treatments.

METHODS

Seven patients with schizophrenia taking risperidone 6 mg/day and nine patients with schizophrenia taking olanzapine 10 mg/day underwent an [123I]IBZM SPECT scan after 3 weeks of treatment. The specific to non-specific equilibrium partition coefficient (V3") after bolus plus constant infusion of the tracer was calculated as [(striatal activity)/(cerebellar activity)]-1. D2 receptor occupancy was calculated by comparing V3" measured in treated patients to an age-corrected V3" value derived from a group of untreated patients with schizophrenia, previously published, according to the following formula: OCC=1-(V3" treated/V3" drug free).

RESULTS

V3" was significantly lower in risperidone treated patients compared with olanzapine treated patients (0.23+/-0.06 versus 0.34+/-0.08, P=-0.01), which translated to a significantly larger occupancy in schizophrenic patients treated with risperidone compared to olanzapine (69+/-8% versus 55 +/-11%, P=0.01). Data from our previous study were used to calculate the occupancy of striatal D2 receptors by antipsychotic medications required to reduce the occupancy of these receptors by endogenous dopamine to control values. In medication-free patients with schizophrenia, the occupancy of striatal D2 receptors by endogenous dopamine is estimated at 15.8%. In healthy controls, the occupancy of striatal D2 receptors by dopamine is estimated at 8.8%. In order to reduce the dopamine occupancy of striatal D2 receptors in patients with schizophrenia to control values, 48% receptor occupancy by antipsychotic medications is required.

CONCLUSIONS

These data indicate that the dosage of these medications, found to be effective in the treatment of schizophrenia, reduces DA stimulation of D2 receptors to levels slightly lower than those found in unmedicated healthy subjects.

Combination of "atypical" antipsychotic medication in the management of treatment-resistant schizophrenia and schizoaffective disorder

BACKGROUND

This article reviews the published clinical data on treatment-resistant schizophrenic and schizoaffective patients managed with combinations of "atypical" antipsychotic medication.

METHOD

A computerized MEDLINE literature search covering an 18-year period (1985-2003) was conducted. All pertinent papers on the subject of the use of combination "atypical" antipsychotic medication in the management of treatment-resistant schizophrenia and schizoaffective disorder were obtained with subsequent analysis and discussion of the retrieved data.

RESULTS

The search identified 29 case reports and case series reports (172 patients) and one double-blind placebo-controlled trial (28 patients) describing the use of combination "atypical" antipsychotic medication (clozapine-risperidone; clozapine-sulpiride; clozapine-olanzapine; clozapine-quetiapine; olanzapine-sulpiride; olanzapine-quetiapine; risperidone-olanzapine; risperidone-quetiapine) in the treatment of resistant schizophrenic and schizoaffective patients. An overview of results suggests that the combinations were beneficial in the described patients with reduction of positive symptoms and occasionally negative symptoms. Significant adverse effects, while rare, were reported in a few cases and did not appear to different in nature from those managed on monotherapeutic regimens.

CONCLUSION

Combinations of "atypical" antipsychotic medications are well tolerated and may be effective in the management of treatment refractory schizophrenia and schizoaffective disorder. However, further double-blind placebo-controlled trials are required in order to test and confirm these observations.

High-dose olanzapine for treatment-refractory schizophrenia

To date there is no common or adequate therapeutic strategy for treatment of refractory schizophrenic patients. Increasing antipsychotics' doses in treatment-resistant schizophrenic patients is the most common intervention used by clinicians. Olanzapine is an atypical antipsychotic, which in a number of double-blind, placebo-controlled studies has been found to be more effective than haloperidol for the treatment of positive and negative symptoms of schizophrenia. During the last few years there have been several reports of successful results in prescribing olanzapine at dosages of more than 25 mg/day for treatment-resistant schizophrenic and schizoaffective patients. This report presents the results from the treatment of three resistant schizophrenic patients treated successfully with high dosages of olanzapine (35, 40, and 60 mg/day). None of the patients had any side effects, including abnormal laboratory levels and weight gain. The results and literature data suggest that in clinical practice some schizophrenic patients resistant to conventional neuroleptic treatment and not responding to olanzapine at recommended dosages as high as 20 mg/day may respond to higher dosages such as 40 or 60 mg/day, and these dosages are well tolerated. Further prospective clinical studies are needed.

Molecular aspects of glutamate dysregulation: implications for schizophrenia and its treatment

The glutamate system is involved in many aspects of neuronal synaptic strength and function during development and throughout life. Synapse formation in early brain development, synapse maintenance, and synaptic plasticity are all influenced by the glutamate system. The number of neurons and the number of their connections are determined by the activity of the glutamate system and its receptors. Malfunctions of the glutamate system affect neuroplasticity and can cause neuronal toxicity. In schizophrenia, many glutamate-regulated processes seem to be perturbed. Abnormal neuronal development, abnormal synaptic plasticity, and neurodegeneration have been proposed to be causal or contributing factors in schizophrenia. Interestingly, it seems that the glutamate system is dysregulated and that N-methyl-D-aspartate receptors operate at reduced activity. Here we discuss how the molecular aspects of glutamate malfunction can explain some of the neuropathology observed in schizophrenia, and how the available treatment intervenes through the glutamate system.

Olanzapine for schizophrenia

BACKGROUND

Olanzapine is an atypical antipsychotic that is reported to be effective without producing the disabling extrapyramidal side effects associated with the older, typical antipsychotic drugs.

OBJECTIVES

To determine the clinical effects and safety of olanzapine as compared with placebo, typical and other atypical antipsychotic drugs for schizophrenia and schizophreniform psychoses.

SEARCH STRATEGY

The reviewers undertook electronic searches of Biological Abstracts (1980-1999), The Cochrane Library (Issue 2, 1999), EMBASE (1980-1999), MEDLINE (1966-1999), PsycLIT (1974-1999) and The Cochrane Schizophrenia Group's Register (October 2000). References of all identified studies were searched for further trials, and the reviewers contacted relevant pharmaceutical companies and authors of trials.

SELECTION CRITERIA

All randomised clinical trials comparing olanzapine to placebo or any antipsychotic treatment for those with schizophrenia or schizophreniform psychoses.

DATA COLLECTION AND ANALYSIS

Data were independently extracted. For homogeneous dichotomous data the random effects relative risk (RR), the 95% confidence intervals (CI) and, where appropriate, the number needed to treat (NNT) were calculated on an intention-to-treat basis. For continuous data the reviewers calculated weighted mean differences.

MAIN RESULTS

Twenty one trials are included. Attrition from olanzapine versus placebo studies was so great (olanzapine - 61%, placebo - 73% by six weeks, RR 0.85 CI 0.7-0.98, NNT 8 CI 5-40) that interpretation of results is problematic. Olanzapine appeared superior to placebo at six weeks for the outcome of 'no important clinical response' (RR 0.88 CI 0.8-0.98, NNT 8 CI 5-27) and global mental state scores. Although dizziness and dry mouth were reported more frequently in the olanzapine-treated group, this did not reach statistical significance. Tthe olanzapine group gained more weight. When compared to typical antipsychotic drugs, data from several small trials are incomplete; but, for the short term outcome of 'no important clinical response', olanzapine seem as effective as typical antipsychotics (n=2778, RR 0.9 CI 0.76-1.06). Brief Psychiatric Rating Scale (BPRS) data tended to be equivocal but Positive and Negative Syndrome Scale (PANSS) rating of total score and negative and positive symptom sub-scores favoured olanzapine. With high attrition in both groups (olanzapine - 36%, typical drug - 49% by 6 weeks, n=2738, RR 0.85 CI 0.66-1.1; olanzapine - 83%, typical drug - 90% by 1 year, n=2738, RR 0.9 CI 0.86-1.02), the assumptions included in all continuous data are considerable. Participants allocated olanzapine experienced fewer extrapyramidal side effects than people given haloperidol. Weight change data for the short term are not conclusive (n=2455, WMD 0.8kg CI -0.6-2.2) but the three to 12 month results suggest an average gain of four kilograms (n=233, WMD 4 CI 0.3-7.8). It is difficult to distinguish between olanzapine and other atypical drugs, although it may cause fewer extrapyramidal side effects than risperidone (n=339, RR 0.6 CI 0.4-0.9, NNH 8 CI 4-29). Olanzapine did cause more weight gain than its comparators but current data are not statistically significant (3-12 months, n=535, WMD 2.2kg CI -0.6-5). One study (n=180) found no clear differences between olanzapine and clozapine for people with treatment-resistant illness.

REVIEWER'S CONCLUSIONS

The large proportions of participants leaving the studies early, in the large multi-centre trials makes it difficult to draw firm conclusions on clinical effects. For people with schizophrenia olanzapine may offer antipsychotic efficacy with fewer extrapyramidal side effects than typical drugs but more weight gain. Large, long-term randomised trials with participants, interventions and primary outcomes that are familiar to those wishing to help those with schizophrenia are long overdue.

Can antipsychotic drugs be classified by their effects on a particular group of dopamine neurons in the brain?

During the four decades that research has been carried out on antipsychotic drugs, a variety of methods have been used to study the effects of these compounds on dopamine neurotransmission. An important issue in this research was to find an explanation for the difference between "typical" and "atypical" antipsychotic drugs. The hypothesis that the beneficial properties and the motor side effects of antipsychotic drugs result from their effects on different groups of dopamine neurons has received considerable attention. Numerous researchers have tried to discover regiospecific actions of antipsychotic drugs in mesolimbic and in mesocortical dopamine neurons. An overview of these research attempts is presented here. Electrophysiological studies showed a selective action of atypical antipsychotic drugs on A10 dopamine neurons. It was found that chronic treatment with these compounds induced a preferential depolarisation block of the A10 neurons that project to the mesolimbic areas. The model represents certain clinical features of antipsychotic drug use and offers a possible explanation for the lack of extrapyramidal side effects of atypical antipsychotic drugs. Dopamine neurons projecting from A10 to the frontal cortex are also considered as a possible site of action of atypical antipsychotic drugs. Microdialysis studies have shown that certain atypical antipsychotic drugs selectively enhance the release of dopamine in the prefrontal cortex when compared with typical antipsychotic drugs. The finding that repeated treatment with antipsychotic drugs increased dopamine D(2) receptor binding in the frontal cortex confirms the significance of this brain area. These properties might indeed explain certain beneficial effects of atypical antipsychotic drugs such as improvement of cognitive dysfunction. However the effects of typical and atypical antipsychotic drugs in the frontal cortex could not be fully differentiated, which illustrates the difficulty of localising clinical effects of antipsychotic drugs in terms of regional dopamine neurons. Recently new insights into the mechanism of action of typical and atypical antipsychotic drugs have been published. Clinical positron emission tomography (PET) studies have indicated that a moderate dopamine D(2) receptor occupancy, probably combined with a high dissociation rate, might provide the optimal clinical conditions for an antipsychotic drug, without inducing extrapyramidal side effects. Moreover the efficacy of benzamides as atypical antipsychotic drugs suggests that low to moderate dopamine D(2) blockade is probably the most important-if not the only-criterion that determines "atypicality". Interestingly these new insights are based on PET studies of the human basal ganglia and not on the comparison of different brain areas. Apparently, according to this concept an ideal antipsychotic drug need not to act on a particular type of dopamine neurons, as it is the moderate dopamine D(2) receptor occupancy that determines the desirable clinical effects. It is concluded that both beneficial actions and side effects, of antipsychotic drugs might be dose dependently localised in A9 as well as A10 dopamine neurons.

The effect of chronic treatment with typical and atypical antipsychotics on working memory and jaw movements in three- and eighteen-month-old rats

The effects of chronic treatment with typical and atypical antipsychotics on acquisition, working memory, motor activity, and rat tardive dyskinesia (TD) were studied in 3- and 18-month-old Sprague-Dawley rats. Acquisition and working memory were studied in eight-arm radial mazes. TD liability of antipsychotic drugs (APD) was evaluated in rat model of TD in which spontaneous repetitive jaw movements (RJM) occur during withdrawal from neuroleptic treatment. Motor behavior was assessed using the traverse beam test. D1 and D2 receptor occupancy was determined in the rat brain during treatment with typical and atypical antipsychotics. Chronic administration of clozapine, haloperidol, and risperidone impaired acquisition of the eight-arm radial maze in both young and aging rats while olanzapine had no effect. Retention tests showed that aging rats made more errors than the adults and that the antipsychotics haloperidol and risperidone significantly impaired retention in both age groups. Evaluation of motor behavior revealed that typical and atypical antipsychotics used in comparable doses in young rats had no effect on motor behavior, whereas in aging rats performance was impaired by clozapine, haloperidol, and risperidone but not by olanzapine. RJM responses were increased during washout from haloperidol treatment in young and aging rats whereas olanzapine, clozapine, and risperidone had no effect. D2 receptor occupancy in haloperidol- and risperidone-treated rats was above 70% while olanzapine and clozapine receptor occupancy was below 70%, which is the threshold for the appearance of extrapyramidal syndrome (EPS) and TD.

Striatal dopamine D2 receptor binding of risperidone in schizophrenic patients as assessed by 123I-iodobenzamide SPECT: a comparative study with olanzapine

The aim of this investigation was to compare the degree of striatal dopamine-(D2) receptor blockade by two atypical antipsychotic drugs, risperidone and olanzapine. The percentage of D2 receptor occupancy during treatment was calculated by comparing the results of 123I-iodobenzamide SPECT with those from healthy control subjects. Twenty inpatients suffering from schizophrenia or schizoaffective psychosis according to DSM IV/ICD-10 criteria were treated with clinically recommended doses of risperidone and compared with 13 inpatients treated with up to 20 mg olanzapine. Neuroleptic dose and D2 receptor blockade correlated strongly for both risperidone (Pearson r = -0.86, p = 0.0001) and olanzapine (Pearson r = -0.77, p = 0.002). There was no significant difference between the D2 receptor occupancy of the two substances when given in the clinically recommended dose range (unpaired t-test, t = -0.112, p = 0.911).

Receptor and transporter imaging studies in schizophrenia, depression, bulimia and Tourette's disorder--implications for psychopharmacology

Considerable progress has been achieved over the past 15 years in uncovering the biological basis of major psychiatric disorders. To determine patterns of brain dysfunction and to uncover the mechanism of action of centrally active compounds we used single photon emission computerized tomography (SPECT) as well as positron emission tomography (PET) in patients diagnosed with schizophrenia, depression, bulimia and Tourette's disorder. Striatal D2 and 5-HT1A receptors were studied in schizophrenia and 5-HT transporters (5-HTT) in depression and bulimia. Patients were either drug-naïve or drug free, or we studied the influence of specifically acting compounds on receptor/transporter occupancy. We could demonstrate that atypical antipsychotics have a dose-dependent (with the exception of clozapine and quetiapine) lower striatal D2 receptor occupancy rate compared with typical neuroleptics, paralleling the more favourable extrapyramidal side effects of atypical antipsychotics. However, no association between striatal D2 receptor occupancy rates and antipsychotic efficacy has been found. The measurement of 5-HT1A receptors in drug-naïve schizophrenic patients using the in vivo PET methodology revealed an increase of cortical 5-HT1A receptor binding potential in schizophrenia. beta-CIT as a ligand for measurement of 5-HT transporter densities (5-HTT) revealed lower rates in depression compared to age- and sex-matching healthy controls, a measurement that has also been obtained for bulimia. We also documented seasonal variations in brain serotonergic function by our finding of reduced brain 5-HTT availability in winter (compared to summer) in healthy controls. Furthermore, displaceable [123I] beta-CIT binding in the area corresponding to the left striatum (representing predominantly the density of dopamine transporters) was significantly reduced in SAD patients compared to healthy controls. In depression as well as in bulimia, selective serotonin reuptake inhibitors significantly decreased the beta-CIT binding potential, however, no significant dose relationship has been obtained in depression. Genotyping depressed patients for the serotonin transporter promoter gene region (5-HTTLPR) did not provide evidence for in vivo functional regulation of 5-HTT availability by 5-HTTLPR in the thalamus-hypothalamus and mesencephalon-pons of healthy subjects. In patients suffering from Tourette's disorder (TD) we were unable to detect differences of dopamine transporter densities between psychotropic drug-naïve TD patients and controls. Furthermore, no difference could be found between currently treated (with antipsychotics) and psychotropic drug-naïve TD patients. Our data provide insight into the pathophysiology of neuropsychiatric disorders and may guide future psychopharmacological drug developments.

Atypical Antipsychotics: Mechanism of Action

Background:

Al though the prin ci pal brain tar get that all an tipsy chotic drugs at tach to is the do pamine D2 re cep tor, tra di tional or typi cal an tipsy chot ics, by at tach ing to it, in duce ex tra py r a mi dal signs and symp toms (EPS). They also, by bind ing to the D2 re cep tor, ele vate se rum pro lac tin. Atypi cal a ntipsy chot ics given in dos ages within the clini cally ef fec tive range do not bring about these adverse clini cal ef fects. To un der stand how these drugs work, it is im por tant to ex am ine the atypical an tipsychot ics' mecha nism of ac tion and how it dif fers from that of the more typi cal drugs.

Method:

This re view analy zes the af fini ties, the oc cu pan cies, and the dis so cia tion time- course of vari ous an tipsy chot ics at do pa mine D2 re cep tors and at se ro tonin (5-HT) re cep tors, both in the test tube and in live pa tients.

Results:

Of the 31 an tipsy chot ics ex am ined, the older tra di tional an tipsy chot ics such as tri fluperazine, pi mozide, chlor pro maz ine, fluphe nazine, ha loperi dol, and flupen thixol bind more tightly than dopamine it self to the do pa mine D2 re cep tor, with dis so cia tion con stants that are lower than that for do pa mine. The newer, atypi cal an tipsy chot ics such as queti apine, re moxi pride, clo zapine, ol a nzap ine, sert in dole, zi pra si done, and amisul pride all bind more loosely than do pa mine to the do pamine D 2 re cep tor and have dis so cia tion con stants higher than that for do pa mine. These tight and loose bind ing data agree with the rates of an tipsy chotic dis so cia tion from the human- cloned D2 recep tor. For in stance, ra dio ac tive ha loperi dol, chlor pro maz ine, and ra clo pride all dis s o ci ate very slowly over a 30- minute time span, while ra dio ac tive queti apine, clo zap ine, re moxi pride, and amisul pride dis so ci ate rap idly, in less than 60 sec onds. These data also match clini cal brain-imaging find ings that show ha loperi dol re main ing con stantly bound to D2 in hu mans un der go ing 2 posi tron emis sion to mo gra phy (PET) scans 24 hours apart. Con versely, the oc cu pa tion of D2 by clo zap ine or queti apine has mostly dis ap peared af ter 24 hours.

Conclusion:

Atypi cals clini cally help pa tients by tran siently oc cu py ing D2 re cep tors and then rap idly dis so ci at ing to al low nor mal do pa mine neu ro trans mis sion. This keeps pro lac tin lev els nor mal, spares cog ni tion, and ob vi ates EPS. One the ory of atypi cal ity is that the newer drugs block 5-HT2A re ceptors at the same time as they block do pa mine re cep tors and that, some how, this serotonin- dopam i n e bal ance con fers atypi cal ity. This, how ever, is not borne out by the re sults. While 5-HT2A re cep tors are read ily blocked at low dos ages of most atypi cal an tipsy chotic drugs (with the im por tant ex ceptions of re moxi pride and amisul pride, nei ther of which is avail able for use in Can ada) the do s ages at which this hap pens are be low those needed to al le vi ate psy cho sis. In fact, the an tipsy chotic thresh old oc cu pancy of D 2 for an tipsy chotic ac tion re mains at about 65% for both typi cal and atypi cal an tipsychotic drugs, re gard less of whether 5-HT2A re cep tors are blocked or not. At the same time, the a ntipsy chotic thresh old oc cu pancy of D2 for elic it ing EPS re mains at about 80% for both typi cal and atypi cal an tipsy chot ics, re gard less of the oc cu pancy of 5-HT2A re cep tors.

Relevance:

The “fast- off-D 2” the ory, on the other hand, pre dicts which an tipsy chotic com pounds will or will not pro duce EPS and hy per pro lac ti ne mia and which com pounds pres ent a rela tiv ely low risk for tar dive dyski ne sia. This the ory also ex plains why L- dopa psy cho sis re sponds t o low atypi cal an tipsy chotic dos ages, and it sug gests vari ous in di vidu al ized treat ment strategies.

Choosing the right dose of antipsychotics in schizophrenia: lessons from neuroimaging studies

Despite vast clinical experience with antipsychotics, there is no broad consensus on the doses of these substances that should be administered. Currently, most antipsychotics are administered empirically according to clinical dose-finding studies, in which arbitrarily selected doses were tested to find the "most efficient" dose range in a patient population, with no regard for the molecular effects of the tested drug. Brain imaging studies using nuclear medical techniques, such as positron emission tomography (PET) or single photon emission computed tomography (SPECT), can now provide a rationale for doses, directly derived from the central effects of the drugs on neurotransmitter receptors measured in vivo. PET results indicate that occupancy of at least 65% of dopamine D(2) receptors is needed for clinical response to antipsychotics, and that occupancy rates exceeding 72 and 78% are associated with a high risk for elevation of prolactin levels and motor adverse effects, respectively. For example, clinical studies with haloperidol do not point to an advantage of dosages exceeding 5 mg/day. The relevance of D(2) receptor occupancy for drug administration is also borne out by studies relating the effects of antipsychotics to their D(2) receptor occupancy in relevant animal models. Taken together, neuroimaging and clinical studies, as well as animal models, provide a rationale for the use of relatively low doses of typical antipsychotics and equivalent doses of novel antipsychotics. The lower risk of adverse effects with appropriate doses of antipsychotics may further enhance compliance and outcome. This seems to be particularly important in individuals experiencing a first episode of schizophrenia, as they appear to be especially responsive to pharmacotherapy and quite sensitive to adverse effects.

Are atypical antipsychotic drugs also atypical antidepressants?

OBJECTIVE

To report a case series and review the psychopharmacology of the neuroleptic drugs to suggest that the atypical antipsychotic drugs may have an antidepressant action, at least for those patients with the melancholic subtype.

METHOD

We note the literature suggesting that the older (or typical) antipsychotic drugs were established as having antidepressant activity, describe an open study of some two dozen patients with a treatment-resistant melancholic depression, describe rapid resolution of depression and augmentation benefits associated with commencing an atypical antipsychotic drug in a percentage of subjects, and then review relevant psychopharmacological studies to consider whether there is a rationale for use of antipsychotic drugs to treat depression.

RESULTS

Of some two dozen patients treated with an atypical antipsychotic drug, almost immediate improvement was noted in four patients, and evidence of augmentation benefit obtained in another three patients.

CONCLUSIONS

Impressions from this case series are encouraging. However, as open clinical observational studies are problematic, controlled studies are required to establish whether the atypical antipsychotic drugs have a role in the management of certain expressions of depression, and, in particular, treatment-resistant melancholic depression.

Double-blind olanzapine vs. haloperidol D2 dopamine receptor blockade in schizophrenic patients: a baseline-endpoint

The aim of this study was to compare in vivo striatal D2 dopamine receptor occupancy induced by olanzapine and haloperidol in schizophrenic patients using a baseline-endpoint [(123)I]IBZM single photon computed emission tomography (SPECT) design. The relationships of striatal D2 receptor occupancy with clinical efficacy and extrapyramidal symptoms (EPS) were also assessed. Twenty-seven inpatients with schizophrenia or schizophreniform disorder were included in a 4-week prospective, randomized, double-blind, parallel and comparative clinical trial. Thirteen patients were treated with haloperidol (10 mg/day) and 14 with olanzapine (10 mg/day). Ratings of clinical status and EPS were obtained weekly. The percentage of D2 receptor occupancy was estimated by using basal ganglia (striatum)/frontal cortex IBZM uptake ratios obtained from each patient before and after 4 weeks of maintained antipsychotic treatment. Olanzapine led to a mean striatal D2 receptor occupancy of 49% (range 28-69%), which was significantly lower than that induced by haloperidol (mean 64%, range 46-90%). The baseline-endpoint SPECT design used in this study revealed lower antipsychotic D2 occupancy percentage values than those reported in the literature, using other approaches. The degree of striatal D2 receptor occupancy correlated to the EPS, which predominantly appeared in patients on haloperidol. No relationship was found between the striatal D2 receptor occupancy and clinical improvement. Olanzapine induced a lower striatal D2 occupancy than haloperidol. This low striatal D2 occupancy, together with the lower incidence of EPS in olanzapine-treated patients, contributed to confirm the atypical behavior of this new antipsychotic drug. Nevertheless, conclusions based on SPECT-estimated percentages of antipsychotic D2 occupancy should be cautious, since the SPECT design could influence the results. In this regard, SPECT studies including baseline and endpoint examinations should be encouraged.

Effects of olanzapine and haloperidol on serum prolactin levels in male schizophrenic patients

It has been proposed that new atypical antipsychotics cause minimal prolactin (PRL) elevation compared to traditional antipsychotic agents because they spare dopamine blockade within the brain's tuberoinfundibular tract. The aim of this study was to compare the effects of olanzapine and haloperidol on PRL secretion in male schizophrenic patients. Twenty-nine male schizophrenic inpatients were included in the study. Fifteen of them were given olanzapine in a fixed dose of 10 mg/day PO and 14 of them were given haloperidol in a fixed dose of 10 mg/day PO for 6 weeks after a 2-week drug washout period. Fifteen age-matched healthy control subjects were used as control group. PRL levels were measured both before and after the 6-week treatment period in the patients. At the end of the 6th week, the PRL values observed with olanzapine treatment were significantly less than those observed with haloperidol, but not different from those of the controls. There was a significant positive correlation between the PRL values and the severity of extrapyramidal side effects in only the haloperidol group after the six week's treatment period. Our data indicate that short-term olanzapine treatment at doses of 10 mg/day PO causes minimal elevations in PRL secretion in male schizophrenic patients in contrast to haloperidol. This finding is consistent with the previous reports and may be attributed to olanzapine's differential effects on dopamine neurotransmission.

D2 receptor occupancy under recommended and high doses of olanzapine: an iodine-123-iodobenzamide SPECT study

The aim of this study was to compare the degree of striatal dopamine D2 receptor availability in patients treated with recommended (5-20 mg, mean dose 11.9 +/- 6.3 mg daily) and higher doses (25-40 mg, mean 32.1 +/- 5.6 mg daily) of the novel antipsychotic drug olanzapine by means of [123I] IBZM Single photon emission computed tomography (SPECT). The results were compared to those of a group of 10 untreated, healthy, age- and sex-matched controls. The degree of dopamine D2 receptor occupancy in the patient group was correlated with the presence of extrapyramidal symptoms (EPS). A total of 20 patients who met the DSM III R criteria for schizophrenia or schizoaffective disorder received a clinically effective antipsychotic monotherapy with olanzapine. The mean daily dose of olanzapine ranged from 0.05-0.6 mg/kg body weight. The dopamine D2 receptor binding was reduced in all patients treated with olanzapine. Specific IBZM binding expressed as the [STR-BKG]/BKG ratio ranged from 0.13-0.61 (healthy controls 0.95). The D2 receptor availability revealed an exponential dose-response relationship (r = - 0.85, p < 0.001). The frequency of EPS induced by olanzapine was considerably lower. Only one patient, treated with 40 mg olanzapine, suffered from severe EPS symptoms and had to be given biperiden. There were no significant differences in the presence of EPS symptoms between patients with recommended doses and those with higher doses of olanzapine.

Double-blind comparison of olanzapine versus clozapine in schizophrenic patients clinically eligible for treatment with clozapine

BACKGROUND

The treatment of schizophrenic patients who fail to respond to adequate trials of neuroleptic drugs is a major challenge. Clozapine has been one treatment option; however, it is not universally effective and is limited in its use by safety concerns. With the introduction of newer agents, their performance relative to clozapine is of great clinical interest.

METHODS

The primary objective of this study was to evaluate the efficacy and safety of olanzapine versus clozapine among treatment resistant DSM-IV schizophrenic patients. The study was primarily designed to demonstrate the "noninferiority" of olanzapine compared to clozapine after 18 weeks of double-blind treatment. Conclusions were based on the one-sided lower 95% confidence limit about the treatment effect observed from the primary efficacy variable (Positive and Negative Syndrome Scale [PANSS] Total).

RESULTS

Mean changes from baseline to end point in PANSS Total score, using a last observation carried forward technique, showed that both agents were comparably effective in neuroleptic resistant patients, i.e., demonstrated the "noninferiority" of olanzapine when compared to clozapine. Overall, significantly fewer olanzapine-treated patients (4%) discontinued for an adverse event than their clozapine-treated (14%) counterparts (p =.022). Among spontaneously reported adverse events, increased salivation, constipation, dizziness, and nausea were reported significantly more often among clozapine-treated patients, whereas only dry mouth was reported more often among olanzapine-treated patients.

CONCLUSIONS

Olanzapine was demonstrated to be noninferior to clozapine and better tolerated among resistant schizophrenic patients clinically eligible for treatment with clozapine.

Low-dose olanzapine for levodopa induced dyskinesias

OBJECTIVE

To assess the usefulness of low-dose olanzapine (2.5 to 7. 5 mg/day) for Levodopa-induced-dyskinesias (LID) in patients with PD.

METHODS

Ten patients with PD and LID took part in this randomized, placebo-controlled, double blind, crossover trial. Patients received a 2-week course of olanzapine or placebo in each treatment phase with 1-week washout in between. Dyskinesias were assessed at baseline and after each treatment period with an acute dopaminergic challenge and unified PD rating scale (UPDRS) questionnaires. Patients also kept on/off and dyskinesia diaries for the last 3 days prior to each assessment.

RESULTS

There was a 41% difference in dyskinesia reduction on olanzapine compared to placebo, as measured by objective dyskinesia rating scales (mean percentage reduction abnormal involuntary movement score: 30% versus -11.2%, p < 0.02). Similar differences were demonstrated by patient diaries (mean reduction: 46% versus -2%, p < 0.02) and UPDRS items 32 and 33. Compared with placebo, treatment with olanzapine resulted in significant increases in 'off' time as measured by patient diaries (30% versus 2%) and reported adverse events (1.7 versus 0.1) including increased parkinsonism (1.1 versus 0.1) and a nonsignificant reported increase in drowsiness.

CONCLUSIONS

Low-dose olanzapine is effective in reducing dyskinesias in PD, but even at very low doses can result in unacceptable increases in parkinsonism and 'off' time.

Newer atypical antipsychotic medication versus clozapine for schizophrenia

BACKGROUND

Clozapine is an atypical antipsychotic drug, which is claimed to have superior efficacy and to cause fewer movement disorders. However, clozapine carries a significant risk of serious blood disorders. Newer atypical antipsychotics are safer alternatives that might share the benefits of clozapine. It is thus of interest to compare the effectiveness of newer atypical antipsychotics with the effectiveness of clozapine.

OBJECTIVES

To evaluate the clinical effects of newer atypical antipsychotic drugs in comparison to clozapine for schizophrenia.

SEARCH STRATEGY

Publications in all languages were searched from the following databases: Biological Abstracts/BIOSIS (1980-1999), The Cochrane Schizophrenia Group's Register of Trials (1998), The Cochrane Library CENTRAL Register (Issue 4, 1999), EMBASE (1980-1998), MEDLINE (1966-1999), LILACS/CD-ROM (1998), and PsycLIT/PsycINFO (1974-1999). Trials were also sought from recent conference proceedings and reference lists of included papers. Authors of recent trials and the manufacturers of clozapine, iloperidone, olanzapine, quetiapine, remoxipride, risperidone, sertindole, ziprasidone and zotepine were contacted.

SELECTION CRITERIA

All randomised controlled trials comparing clozapine with newer atypical antipsychotic drugs were included by independent assessment by two reviewers.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two reviewers. Relative risks (RR) and 95% confidence intervals (CI) of homogenous dichotomous data were calculated. A random effects model was used for heterogeneous dichotomous data. Where possible the number needed to treat (NNT) statistic with 95%CI were also calculated. Weighted or standardised means were calculated for continuous data. Due to the small number of included studies, sensitivity analyses or funnel plot statistics were not undertaken for this version of the review.

MAIN RESULTS

The current review includes eight studies (22 papers), of which three studies are 4-6 weeks in duration and only one study is of more than 12 weeks' duration. Newer atypical drugs seemed to be broadly similar to clozapine using a clinical global index or trialists' definitions of improvement, but this result was obtained from a relatively small number of studies. Due to the small number of studies and patients, wide confidence intervals were seen when their effectiveness as measured by symptom rating scales was compared. Social functioning was better in patients on newer atypical medication (risperidone) than in those on clozapine, but this finding is based on a single underpowered trial and has to be interpreted with caution. Clozapine and newer atypical drugs showed their adverse effect profile to be dissimilar: while clozapine produced more fatigue, hypersalivation, nausea, and orthostatic dizziness, new atypical drugs, with the exception of olanzapine, produced more extrapyramidal symptoms. The impact of these drugs and their effects on patients' day-to-day quality of life, service use, hospital admission, and pharmacoeconomics was not measured.

REVIEWER'S CONCLUSIONS

The equal effectiveness and tolerability of new atypical drugs in comparison with clozapine is not yet demonstrated. Lack of statistical power to determine the comparative efficacy and effectiveness of newer atypical drugs makes it difficult to judge whether newer drugs are more effective, less effective or equivalent. Trials of sufficient power, with longer duration, measuring clinically important outcomes, are needed to assess the true comparative clinical effectiveness, tolerability and cost effectiveness of newer drugs in relation to clozapine.

Dopamine D2 receptor occupancy by olanzapine or risperidone in young patients with schizophrenia

A crucial characteristic of antipsychotic medication is the occupancy of the dopamine (DA) D2 receptor. We assessed striatal DA D2 receptor occupancy by olanzapine and risperidone in 36 young patients [31 males, 5 females; mean age 21.1 years (16-28)] with first episode schizophrenia, using [123I]iodobenzamide (IBZM) SPECT. The occupancy of DA D2 receptors was not significantly different between olanzapine and risperidone. However, in subgroups of most prescribed doses, DA D2 occupancy was higher in the risperidone 4-mg group (79%) compared to the olanzapine 15-mg group (62%). [123I]IBZM binding ratios decreased with olanzapine dose (r = -0.551; P < 0.01), indicating higher DA D2 receptor occupancy with higher olanzapine dose. Akathisia and positive symptoms were correlated with [123I]IBZM binding ratio (r = -0.442; P < 0.01; and r = -0.360; P < 0.05, respectively). Prolactin (PRL) levels were elevated in the risperidone, but not in the olanzapine group, at comparable D2 receptor occupancy levels. In the olanzapine group, PRL levels were correlated with [123I]IBZM binding ratio (r = -0.551; P < 0.01). In conclusion, both olanzapine and risperidone induce a high striatal D2 receptor occupancy, dependent on dose and group formation. The lower incidence of prolactin elevation with olanzapine, compared to risperidone, may not be attributed to a lower D2 receptor occupancy.

The effect of novel antipsychotics in rat oral dyskinesia

1. The effect of the D1 agonist SKF38393 and the 5HT2C agonist m-CPP on repetitive jaw movements (RJM) was studied in rats. Acute administration of SKF38393 and/or m-CPP induced RJM in a dose dependent manner. In rats treated with both drugs, RJM responses were about equal to the sum of those obtained with each drug alone. 2. The induction of RJM by SKF38393 was somewhat lower in rats pretreated with 5HT2C receptor antagonist, mianserin, whereas mianserin severely reduced RJM induced by m-CPP alone. 3. D1 antagonist SCH23390 inhibited SKF38393 induced RJM but had no effect on m-CPP induced chewing behavior. 4. The present study confirms earlier evidence that D1 agonists used at optimal doses for the induction of RJM do not involve the serotonergic system in a significant way. It does, however, implicate the system in the emergence of drug induced oral behavior in rats. 5. The effect of the atypical antipsychotics, clozapine, olanzapine and risperidone was studied on SKF38393 and m-CPP induced RJM. Pretreatment with the atypical antipsychotics clozapine and olanzapine inhibit SKF38393 and m-CPP induced RJM. Pretreatment with risperidone inhibits m-CPP induced oral behavior in rats while increases dose dependently SKF38393 induced RJM.

Caudate size in first-episode neuroleptic-naive schizophrenic patients measured using an artificial neural network

BACKGROUND

Structural brain imaging studies have demonstrated an increase in caudate volume in schizophrenic patients medicated with typical neuroleptics and a volume decrease following treatment with atypical neuroleptics. The measurement of striatal volume in patients who have never been treated with neuroleptics may indicate whether these changes are superimposed on intrinsic basal ganglia pathology in schizophrenia or are solely neuroleptic-induced.

METHODS

We studied 36 first-episode, neuroleptic-naive schizophrenic patients and 43 control subjects using an artificial neural network (ANN) to identify and measure the caudate nucleus. The resulting volumes were analyzed using an ANCOVA controlling for intracranial volume, age, gender, and socioeconomic status.

RESULTS

The mean volume difference between the caudate nuclei of patients and control subjects was .297 mL, the caudate nuclei of the patients being smaller than those of controls. When we covaried for intracranial volume, this was a statistically significant difference in caudate volume (n = 79; df = 1,75; F = 4.18; p > .04).

CONCLUSIONS

Caudate nuclei of neuroleptic naive schizophrenic patients are significantly smaller than those of controls. This suggests that patients suffering from schizophrenia may have intrinsic pathology of the caudate nucleus, in addition to the pathology observed as a consequence of chronic neuroleptic treatment.

Olanzapine. Pharmacokinetic and pharmacodynamic profile

Multicentre trials in patients with schizophrenia confirm that olanzapine is a novel antipsychotic agent with broad efficacy, eliciting a response in both the positive and negative symptoms of schizophrenia. Compared with traditional antipsychotic agents, olanzapine causes a lower incidence of extrapyramidal symptoms and minimal perturbation of prolactin levels. Generally, olanzapine is well tolerated. The pharmacokinetics of olanzapine are linear and dose-proportional within the approved dosage range. Its mean half-life in healthy individuals was 33 hours, ranging from 21 to 54 hours. The mean apparent plasma clearance was 26 L/h, ranging from 12 to 47 L/h. Smokers and men have a higher clearance of olanzapine than women and nonsmokers. After administering [14C]olanzapine, approximately 60% of the radioactivity was excreted in urine and 30% in faeces. Olanzapine is predominantly bound to albumin (90%) and alpha 1-acid glycoprotein (77%). Olanzapine is metabolised to its 10- and 4'-N-glucuronides, 4'-N-desmethylolanzapine [cytochrome P450 (CYP) 1A2] and olanzapine N-oxide (flavin mono-oxygenase 3). Metabolism to 2-hydroxymethylolanzapine via CYP2D6 is a minor pathway. The 10-N-glucuronide is the most abundant metabolite, but formation of 4'-N-desmethylolanzapine is correlated with the clearance of olanzapine. Olanzapine does not inhibit CYP isozymes. No clinically significant metabolic interactions were found between olanzapine and diazepam, alcohol (ethanol), imipramine, R/S-warfarin, aminophylline, biperiden, lithium or fluoxetine. Fluvoxamine, an inhibitor of CYP1A2, increases plasma concentrations of olanzapine; inducers of CYP1A2, including tobacco smoke and carbamazepine, decrease olanzapine concentrations. Orthostatic changes were observed when olanzapine and diazepam or alcohol were coadministered. Pharmacodynamic interactions occurred between olanzapine and alcohol, and olanzapine and imipramine, implying that patients should avoid operating hazardous equipment or driving an automobile while experiencing the short term effects of the combinations. Individual factors with the largest impact on olanzapine pharmacokinetics are gender and smoking status. The plasma clearance of olanzapine generally varies over a 4-fold range, but the variability in the clearance and concentration of olanzapine does not appear to be associated with the severity or duration of adverse effects or the degree of efficacy. Thus, dosage adjustments appear unnecessary for these individual factors. However, dosage modification should be considered for patients characterised by a combination of factors associated with decreased oxidative metabolism, for example, debilitated or elderly women who are nonsmokers.

Brain SPECT imaging in Huntington's disease before and after therapy with olanzapine. Case report

Olanzapine, an atypical antipsychotic drug, was administered to a patient with Huntington's disease (HD) with marked choreiform movements. Brain SPECT with 99mTc-HMPAO was performed before and after treatment. Brain SPECT imaging has been performed in patients with HD in order to determine the status of basal ganglia perfusion. The use of brain SPECT with 99mTc-HMPAO before and after treatment in patients with HD has not been yet reported. The marked hypoperfusion of the basal ganglia on brain SPECT performed before therapy with olanzapine improved significantly after treatment.

Change in basal ganglia volume over 2 years in patients with schizophrenia: typical versus atypical neuroleptics

OBJECTIVE

For many years, it has been assumed that medications affect brain chemistry and physiology but not structure. Recent reports suggest that neuroleptic medication changes basal ganglia volume. To explore this possibility, the authors assessed for basal ganglia volume change in individuals who had their basal ganglia structures delineated and measured on magnetic resonance scans at the beginning and end of a 2-year period and who received neuroleptic medication during this time.

METHOD

The basal ganglia volumes of 23 male patients with schizophrenia spectrum disorders were measured from manual traces delineating the caudate and lenticular nucleus on magnetic resonance images at admission and 2 years later. Patients' neuroleptic exposure was calculated over the 2 years by using a dose-year formula.

RESULTS

During the 2-year period, mean basal ganglia volume of patients receiving predominantly typical neuroleptics increased, while the opposite was observed for patients receiving mostly atypical neuroleptics. Correlation analysis for the entire group showed a positive relationship between the 2-year exposure to typical neuroleptic medication and change in basal ganglia volume and the reverse for exposure to atypical neuroleptics.

CONCLUSIONS

In this group, basal ganglia volume increased following exposure to typical neuroleptics and decreased following exposure to atypical neuroleptics.

Clinical and theoretical implications of 5-HT2 and D2 receptor occupancy of clozapine, risperidone, and olanzapine in schizophrenia

OBJECTIVE

Dopamine D2 receptor occupancy measurements provide a valid predictor of antipsychotic response, extrapyramidal side effects, and elevation of prolactin levels. The new antipsychotics clozapine, risperidone, and olanzapine obtain antipsychotic response with few extrapyramidal side effects and little prolactin elevation. The purpose of this study was to compare the D2 and serotonin 5-HT2 receptor occupancies of these drugs in patients receiving multiple-dose, steady-state regimens.

METHOD

Forty-four patients with schizophrenia (16 taking risperidone, 2-12 mg/day; 17 taking olanzapine, 5-60 mg/day; and 11 taking clozapine, 75-900 mg/day) had their D2 and 5-HT2 occupancies determined with the use of [11C]raclopride and [18F]setoperone, respectively, and positron emission tomography imaging.

RESULTS

Clozapine showed a much lower D2 occupancy (16%-68%) than risperidone (63%-89%) and olanzapine (43%-89%). Risperidone and olanzapine gave equal D2 occupancies at doses of 5 and 20 mg/day, respectively. All three drugs showed greater 5-HT2 than D2 occupancy at all doses, although the difference was greatest for clozapine.

CONCLUSIONS

Clozapine, at doses known to be effective in routine clinical settings, showed a D2 occupancy clearly lower than that of typical antipsychotics, while risperidone and olanzapine at their usual clinical doses gave the same level of D2 occupancy as low-dose typical antipsychotics. The results also suggest that some previous clinical comparisons of antipsychotics may have been confounded by different levels of D2 occupancy. Clinical comparisons of these drugs, matching for D2 occupancy, may provide a better measure of their true "atypicality" and will help in understanding the contribution of non-D2 receptors to antipsychotic effects.