D(2) and 5HT(2A) receptor occupancy of different doses of quetiapine in schizophrenia: a PET study

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: Focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialised tools are used. Three tools have been proven useful to personalise drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimise treatment effects, minimise side effects and ultimately reduce the global burden of diseases, personalised drug treatment has not yet become the standard of care in psychiatry.

Update Lessons from Positron Emission Tomography Imaging Part I: A Systematic Critical Review on Therapeutic Plasma Concentrations of Antipsychotics

BACKGROUND

Positron emission tomography (PET) and single photon emission tomography (SPECT) of molecular drug targets (neuroreceptors and transporters) provide essential information for therapeutic drug monitoring-guided antipsychotic drug therapy. The optimal therapeutic windows for D 2 antagonists and partial agonists, as well as their proposed target ranges, are discussed based on an up-to-date literature search.

METHODS

This part I of II presents an overview of molecular neuroimaging studies in humans and primates involving the target engagement of amisulpride, haloperidol, clozapine, aripiprazole, olanzapine, quetiapine, risperidone, cariprazine, and ziprasidone. The systemic review particularly focused on dopamine D 2 -like and 5-HT 2A receptors. Target concentration ranges were estimated based on receptor occupancy ranges that relate to clinical effects or side effects (ie, extrapyramidal side effects). In addition, findings for other relevant receptor systems were included to further enrich the discussion.

RESULTS

The reported reference ranges for aripiprazole and clozapine align closely with findings from PET studies. Conversely, for haloperidol, risperidone, and olanzapine, the PET studies indicate that a lowering of the previously published upper limits would be necessary to decrease the risk of extrapyramidal side effect.

CONCLUSIONS

Molecular neuroimaging studies serve as a strong tool for defining target ranges for antipsychotic drug treatment and directing therapeutic drug monitoring.

Psilocybin for Depression: From Credibility to Feasibility, What's Missing?

Psilocybin has been suggested as a promising transdiagnostic treatment strategy for a wide range of psychiatric disorders. Recent findings showed that psychedelic-assisted/"psycholitic" psychotherapy should provide significant and sustained alleviation of depressive symptoms. However, to date, there have been several study limitations (e.g., small sample sizes, blinding, limited follow-up, highly screened treatment populations) and some health/political issues, including practitioners' experience, lack of standardized protocols, psychedelics' legal status, ethical concerns, and potential psychological/psychopathological/medical untoward effects. The focus here is on a range of clinical and methodological issues, also aiming at outlining some possible suggestions. We are confident that newer evidence, more precise protocols, and eventual reclassification policies may allow a better understanding of the real potential of psilocybin as a transdiagnostic therapeutic molecule.

Deprescribing to Resolve Oversedation and Confusion in an Older Person Treated for Auditory Hallucinations and Poststroke Seizure Prophylaxis

This case study reviews the pharmacotherapy of a resident in a long-term care facility being treated for poststroke seizure, hallucinations, and dementia, a geriatric syndrome that is both common in regard to its prevalence and severe in regard to its impact on the individual, families, caregivers, and health care system. This case describes the past medical history of an older resident in a skilled nursing facility that was receiving pharmacological therapy for auditory hallucinations and for poststroke seizure prophylaxis, was noted to be having side effects from drug therapy, and how the nursing staff communicated with the consultant pharmacist to resolve these issues.

Discovery of Nonracemic Amisulpride to Maximize Benefit/Risk of 5-HT7 and D2 Receptor Antagonism for the Treatment of Mood Disorders

In contrast to the dose‐occupancy relationship in the treatment of schizophrenia, the minimal effective level of dopamine receptor 2 (D2R) blockade for antipsychotics in the treatment of bipolar depression is unknown. Lower doses aimed at reducing extrapyramidal side effects must be balanced against the need to retain the therapeutic benefit of D2R blockade on emergent cycling, mixed, manic, anxiety, and/or psychotic symptoms. Dose‐reductions intended to lower D2R blockade, however, could also decrease concomitant serotonin receptor antagonism and its potential benefit on depressive symptoms. Here, we uncoupled the potential antidepressant activity in amisulpride, driven by 5‐HT7 receptor (5‐HT7R) antagonism, from the D2R‐mediated antipsychotic activity by discovering that each enantiomer favors a different receptor. Aramisulpride was more potent at 5‐HT7R relative to esamisulpride (Ki 47 vs. 1,900 nM, respectively), whereas esamisulpride was more potent at D2R (4.0 vs. 140 nM). We hypothesized that a nonracemic ratio might achieve greater 5‐HT7R‐mediated antidepressant effects at a lower level of D2R blockade. The dose‐occupancy relationship of esamisulpride at D2R was determined by positron emission tomography (PET) imaging in human volunteers. Separately the dose‐relationship of aramisulpride was established in humans using suppression of rapid eye movement (REM) sleep as a marker of 5‐HT7R antagonism. These results led to the discovery of an 85:15 ratio of aramisulpride to esamisulpride (SEP‐4199) that maximizes the potential for antidepressant benefit of aramisulpride via 5‐HT7R and reduces esamisulpride to minimize D2R‐related extrapyramidal side effects while still retaining D2R‐mediated effects predicted to provide benefit in bipolar depression. The antidepressant efficacy of SEP‐4199 was recently confirmed in a proof‐of‐concept trial for the treatment of bipolar depression (NCT03543410).

Augmentation with Atypical Antipsychotics for Treatment-Resistant Depression

BACKGROUND

Treatment-resistant depression (TRD) is considered a common clinical condition often associated with relevant suicidal ideation and characterized by a severe functional impairment lifetime. Among the available drugs for the TRD treatment, second-generation antipsychotics (SGAs) have been reported as effective. In this context, the aim of this study was to review the clinical studies evaluating the efficacy of SGAs as add-on therapy in TRD.

METHODS

A comprehensive search on PubMed, Medline and PsychINFO of all randomized clinical trials (RCTs) assessing the augmentation with antipsychotics in TRD, published from January 2000 until March 2020, was performed. Sixteen RCTs studies met the inclusion criteria.

RESULTS

The reviewed studies showed that the add-on therapy with aripiprazole could be beneficial in the treatment of TRD. Furthermore, RCTs on quetiapine augmentation support its use in TRD, especially when comorbid anxiety or insomnia are present. The effects of risperidone and olanzapine as add-on in TRD were less studied, but preliminary data indicated an efficacy respect to placebo, making them a possible therapeutic option in TRD.

LIMITATIONS

The lack of consistency in the definition of TRD together with the small sample sizes and the heterogeneity of antipsychotics dosages used in the reviewed RCTs may have limited the strength of evidences obtained.

CONCLUSION

Overall, the available RCTs studies seem to support the hypothesis that the augmentation with SGAs, in particular aripiprazole and quetiapine, is a valid therapeutic option for TRD. However, to improve the therapeutic outcome of patients with TRD, larger and more homogeneous RCTs are needed.

Methylphenidate challenge test in adults with attention deficit/hyperactivity disorder (ADHD): Clinical effects and their predictors

OBJECTIVE

Adult and children attention deficit/hyperactivity disorder (ADHD) share similar symptoms and responses to drugs such as methylphenidate (MPH). Yet, in Europe, these drugs remain unlicensed for adults. We aimed to assess the effects of an acute MPH challenge on the four dimensions concentration, impulsivity, tension, and general well-being in ADHD adults, and identify predictors of improvement.

METHODS

Therapeutic Drug Monitoring was performed to measure MPH plasma levels. A Visual Analogue Scale was administered to patients before and after the acute MPH challenge to measure self-reported changes in the four dimensions.

RESULTS

After the acute MPH challenge, our 71 patients showed significant improvement in concentration and tension. The MPH challenge dose correlated with lower patients' age, greater side effects, increased concentration (p = .008) and decreased tension (p = .001). At multiple linear regression MPH plasma levels and absence of postdose side effects predicted concentration improvement, MPH plasma levels predicted tension improvement. MPH plasma levels were significantly higher in patients who reported an improvement in concentration, tension, and impulsivity compared to nonimprovers (p's from .001 to .004).

CONCLUSIONS

These findings point to the efficacy of MPH challenge in improving concentration and tension in adult ADHD, thus emphasizing the need for a broader treatment access for these patients.

Factors associated with successful antipsychotic dose reduction in schizophrenia: a systematic review of prospective clinical trials and meta-analysis of randomized controlled trials

This systematic review and meta-analysis examined predictors of successful antipsychotic dose reduction in schizophrenia. Prospective clinical trials and randomized controlled trials (RCTs) investigating antipsychotic dose reduction in schizophrenia were selected for systematic review and meta-analysis, respectively. In total, 37 trials were identified. Only 8 studies focused on second-generation antipsychotics (SGAs); no studies investigated long-acting injectable SGAs. Of 24 studies evaluating relapse or symptom changes, 20 (83.3%) met the criteria for successful dose reduction. Factors associated with successful dose reduction were study duration < 1 year, age > 40 years, duration of illness > 10 years, and post-reduction chlorpromazine equivalent (CPZE) dose > 200 mg/day. Clinical deterioration was mostly re-stabilized by increasing the dose to the baseline level (N = 7/8, 87.5%). A meta-analysis of 18 RCTs revealed that relapse rate was significantly higher in the reduction group than the maintenance group (risk ratio [RR] = 1.96; 95% confidence interval [CI], 1.23-3.12), whereas neurocognition was significantly improved (standardized mean difference = 0.69; 95% CI, 0.25-1.12). A subgroup analysis indicated that only a post-reduction CPZE dose ≤ 200 mg/day was associated with an increased risk of relapse (RR = 2.79; 95% CI, 1.29-6.03). Thus, when reducing antipsychotic doses, clinicians should consider the long-term risk of relapse in younger patients with a relatively short illness duration and keep the final doses higher than CPZE 200 mg/day. Further studies, particularly those involving SGAs, are warranted to determine the optimal strategies for successful antipsychotic dose reduction in schizophrenia.

"Fake it till You Make it"! Contaminating Rubber Hands ("Multisensory Stimulation Therapy") to Treat Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a deeply enigmatic psychiatric condition associated with immense suffering worldwide. Efficacious therapies for OCD, like exposure and response prevention (ERP), are sometimes poorly tolerated by patients. As many as 25% of patients refuse to initiate ERP mainly because they are too anxious to follow exposure procedures. Accordingly, we proposed a simple and tolerable (immersive yet indirect) low-cost technique for treating OCD that we call “multisensory stimulation therapy.” This method involves contaminating a rubber hand during the so-called “rubber hand illusion” (RHI) in which tactile sensations may be perceived as arising from a fake hand. Notably, Jalal et al. (2015) showed that such fake hand contamination during the RHI provokes powerful disgust reactions in healthy volunteers. In the current study, we explored the therapeutic potential of this novel approach. OCD patients (n = 29) watched as their hidden real hand was being stroked together with a visible fake hand; either synchronously (inducing the RHI; i.e., the experimental condition; n = 16) or asynchronously (i.e., the control condition; n = 13). After 5 min of tactile stimulation, the rubber hand was contaminated with fake feces, simulating conventional exposure therapy. Intriguingly, results suggested sensory assimilation of contamination sensations into the body image via the RHI: patients undergoing synchronous stimulation did not report greater contamination sensations when the fake hand was initially contaminated relative to asynchronous stroking. But contrary to expectations, they did so after the rubber hand had been contaminated for 5 min, as assessed via disgust facial expressions (a secondary outcome) and in vivo exposure (upon discontinuing the illusion). Further, to our surprise, synchronous and asynchronous stroking induced an equally vivid and fast-emerging illusion, which helps explain why both conditions initially (5 min after initiating tactile stimulation) provoked contamination reactions of equal magnitude. This study is the first to suggest heightened malleability of body image in OCD. Importantly, it may pave the way for a tolerable technique for the treatment of OCD—highly suitable for poorly resourced and emergency settings, including low-income and developing countries with minimal access to high-tech solutions like virtual reality.

Baseline impulsivity may moderate L-DOPA effects on value-based decision-making

Research has indicated a major role of dopamine in decision-making processes, but the underlying mechanisms remain largely unknown due to inconsistency in effects of dopaminergic drugs. To clarify the impact of dopamine on impulsive choice, we administered 150 mg L-DOPA to 87 healthy adults in a randomized, placebo-controlled, double-blind, crossover study, evaluating performance in four value-based decision-making tasks. We predicted that baseline impulsivity would moderate L-DOPA effects. In support of our hypothesis, L-DOPA had no main effect on impulsive choice, but reduced risk-seeking for gains in more-impulsive subjects. Because L-DOPA effects may be influenced by body weight, we repeated our analyses on data from half of the sample (n = 44) with lower weight, anticipating a stronger effect. In addition to the effect on risk-seeking for gains, low-weight participants also exhibited baseline-dependent effects of L-DOPA on loss aversion and delay discounting. Our results are consistent with the hypothesis of an inverted U-shaped dopamine function in which both low and high extremes of dopamine signaling are associated with high-impulsive choice. Consideration of differential baseline impulsivity and body weight may resolve previous seemingly paradoxical pharmacological results and might deepen our understanding of dopaminergic mechanisms underlying impulsivity.

Dopamine D2 receptor occupancy of lumateperone (ITI-007): a Positron Emission Tomography Study in patients with schizophrenia

Dopamine D₂ receptor occupancy (D₂RO) is a key feature of all currently approved antipsychotic medications. However, antipsychotic efficacy associated with high D₂RO is often limited by side effects such as motor disturbances and hyperprolactinemia. Lumateperone (ITI-007) is a first-in-class selective and simultaneous modulator of serotonin, dopamine and glutamate in development for the treatment of schizophrenia and other disorders. The primary objective of the present study was to determine D₂RO at plasma steady state of 60 mg ITI-007, a dose that previously demonstrated antipsychotic efficacy in a controlled trial, administered orally open-label once daily in the morning for two weeks in patients with schizophrenia (N = 10) and after at least a two-week washout period from standard of care antipsychotics. D₂RO was determined using positron emission tomography with ¹¹C-raclopride as the radiotracer. Mean peak dorsal striatal D₂RO was 39% at 60 mg ITI-007 occurring 1 h post-dose. Lumateperone was well-tolerated with a favorable safety profile in this study. There were no clinically significant changes in vital signs, ECGs, or clinical chemistry laboratory values, including prolactin levels. There were no adverse event reports of akathisia or other extrapyramidal motor side effects; mean scores on motor function scales indicated no motor disturbances with lumateperone treatment. This level of occupancy is lower than most other antipsychotic drugs at their efficacious doses and likely contributes to the favorable safety and tolerability profile of lumateperone with reduced risk for movement disorders and hyperprolactinemia. If approved, lumateperone may provide a new and safe treatment option for individuals living with schizophrenia.

Hypofunctional Dopamine Uptake and Antipsychotic Treatment-Resistant Schizophrenia

Antipsychotic treatment resistance in schizophrenia remains a major issue in psychiatry. Nearly 30% of patients with schizophrenia do not respond to antipsychotic treatment, yet the underlying neurobiological causes are unknown. All effective antipsychotic medications are thought to achieve their efficacy by targeting the dopaminergic system. Here we review early literature describing the fundamental mechanisms of antipsychotic drug efficacy, highlighting mechanistic concepts that have persisted over time. We then reconsider the original framework for understanding antipsychotic efficacy in light of recent advances in our scientific understanding of the dopaminergic effects of antipsychotics. Based on these new insights, we describe a role for the dopamine transporter in the genesis of both antipsychotic therapeutic response and primary resistance. We believe that this discussion will help delineate the dopaminergic nature of antipsychotic treatment-resistant schizophrenia.

Representativeness of clinical PET study participants with schizophrenia: A systematic review

While positron emission tomography (PET) studies have provided invaluable data on antipsychotic effects, selection bias remains a serious concern. A systematic review of PET studies that measured dopamine D₂ receptor blockade with antipsychotics was conducted to examine their inclusion/exclusion criteria, using PubMed, EMBASE, and ClinicalTrials.gov (last search, September 2016). PET studies were included if they measured D₂ receptor occupancy in patients with schizophrenia and included introduction of antipsychotic treatment or antipsychotic regimen change in a systematic manner. Twenty-six studies were identified. Age limit was included in 13 studies; one study solely included geriatric patients while others targeted younger adults. Eleven, 6, and 3 studies specifically targeted clinically stable patients, patients with severe psychopathology, and antipsychotic-free patients, respectively. Nineteen and 18 studies excluded patients with physical comorbidity and substance abuse, respectively. As a result, the mean age of subjects ranged from 23 to 42 years when one study that targeted geriatric patients was excluded. Mean Positive and Negative Syndrome Scale total scores ranged from 54 to 95. No comparison active-drug or placebo arm was employed in 24 studies. Blind assessment of symptomatology was performed in 5 studies. In general, subjects participating in clinical PET studies were relatively young, presented with mild symptomatology, and were free from substance abuse or physical comorbidities. These characteristics need to be taken into account when clinical PET data are interpreted. On the other hand, it should also be noted that this study was only qualitative and conservative interpretation is necessary for possibility of subjective bias.

Neural correlates of the popular music phenomenon: evidence from functional MRI and PET imaging

PURPOSE

Music can induce different emotions. However, its neural mechanism remains unknown. The aim of this study was to use functional magnetic resonance imaging (fMRI) and position emission tomography (PET) imaging for mapping of neural changes under the most popular music in healthy volunteers.

METHODS

Blood-oxygen-level-dependent (BOLD) fMRI and monoamine receptor PET imaging with ¹¹C-N-methylspiperone (¹¹C-NMSP) were conducted under the popular music Gangnam Style and light music A Comme Amour in healthy subjects. PET and fMRI images were analyzed by using the Statistical Parametric Mapping software (SPM).

RESULTS

Significantly increased fMRI BOLD signals were found in the bilateral superior temporal cortices, left cerebellum, left putamen and right thalamus cortex. Monoamine receptor availability was increased significantly in the left superior temporal gyrus and left putamen, but decreased in the bilateral superior occipital cortices under the Gangnam Style compared with the light music condition. Significant positive correlation was found between ¹¹C-NMSP binding and fMRI BOLD signals in the left temporal cortex. Furthermore, increased ¹¹C-NMSP binding in the left putamen was positively correlated with the mood arousal level score under the Gangnam Style condition.

CONCLUSION

Popular music Gangnam Style can arouse pleasure experience and strong emotional response. The left putamen is positively correlated with the mood arousal level score under the Gangnam Style condition. Our results revealed characteristic patterns of brain activity associated with Gangnam Style, and may also provide more general insights into the music-induced emotional processing.

Reversible global aphasia as a side effect of quetiapine: a case report and literature review

Quetiapine is an atypical antipsychotic agent which is also prescribed for delirium due to its anti-dopaminergic effects; aphasia is an unusual side effect associated with the drug. Here, we report the case of an 83-year-old woman who was prescribed quetiapine (50 mg per day) for delirium. Unexpected, global aphasia occurred 3 days after treatment began. Complete recovery occurred following discontinuation of the drug. A brain computed tomography scan excluded intracranial hemorrhage and the laboratory results confirmed that no exacerbation of infection or electrolyte imbalances were present. During the aphasic episode, the patient's condition did not deteriorate and no new neurological symptoms occurred. We suspect that the occurrence of aphasia was directly due to an adverse reaction to quetiapine. To our knowledge, this is the first case report of reversible, global aphasia as a side effect of quetiapine. We propose that this occurrence of aphasia may be due to the action of quetiapine as a dopamine receptor antagonist. Clinicians should use quetiapine with caution, especially in elderly patients. On observation of aphasia, a review of the patient's medical history is required to assess for the usage of quetiapine.

Brain Functional Effects of Psychopharmacological Treatments in Schizophrenia: A Network-based Functional Perspective Beyond Neurotransmitter Systems

Psychopharmacological treatments for schizophrenia have always been a matter of debate and a very important issue in public health given the chronic, relapsing and disabling nature of the disorder. A thorough understanding of the pros and cons of currently available pharmacological treatments for schizophrenia is critical to better capture the features of treatment-refractory clinical pictures and plan the developing of new treatment strategies. This review focuses on brain functional changes induced by antipsychotic drugs as assessed by modern functional neuroimaging techniques (i.e. fMRI, PET, SPECT, MRI spectroscopy). The most important papers on this topic are reviewed in order to draw an ideal map of the main functional changes occurring in the brain during antipsychotic treatment. This supports the hypothesis that a network-based perspective and a functional connectivity approach are needed to fill the currently existing gap of knowledge in the field of psychotropic drugs and their mechanisms of action beyond neurotransmitter systems.

Baseline Perfusion Alterations Due to Acute Application of Quetiapine and Pramipexole in Healthy Adults

BACKGROUND

The dopaminergic system is implicated in many mental processes and neuropsychiatric disorders. Pharmacologically, drugs with dopamine receptor antagonistic and agonistic effects are used, but their effects on functional brain metabolism are not well known.

METHODS

In this randomized crossover, placebo-controlled, and rater-blinded study, 25 healthy adults received an acute dose placebo substance (starch), quetiapine (dopamine receptor antagonist), or pramipexole (dopamine agonist of the nonergoline class) 1 hour before the experiment. Background-suppressed 2D pseudo-continuous arterial spin labeling was used to examine whole-brain baseline cerebral blood flow differences induced by the 3 substances.

RESULTS

We found that quetiapine reduced perfusion in the occipital (early visual areas) and bilateral cerebellar cortex relative to placebo. In contrast, quetiapine enhanced cerebral blood flow (relative to placebo) in the striatal system (putamen and caudate nucleus) but also in the supplementary motor area, insular-, prefrontal- as well as in the pre- and postcentral cortex. Pramipexole increased cerebral blood flow compared with placebo in the caudate nucleus, putamen, middle frontal, supplementary motor area, and brainstem (substantia nigra), but reduced cerebral blood flow in the posterior thalamus, cerebellum, and visual areas. Pramipexole administration resulted in stronger cerebral blood flow relative to quetiapine in the hypothalamus, cerebellum, and substantia nigra.

CONCLUSIONS

Our results indicate that quetiapine and pramipexole differentially modulate regional baseline cerebral blood flow. Both substances act on the dopaminergic system, although they affect distinct regions. Quetiapine altered dopaminergic function in frontal, striatal, and motor regions. In contrast, pramipexole affected cerebral blood flow of the nigrostriatal (striatum and substantia nigra) dopaminergic, but less the fronto-insular system.

Histamine H1 receptor occupancy by the new-generation antipsychotics olanzapine and quetiapine: a positron emission tomography study in healthy volunteers

RATIONALE

Histamine H1 antagonists have hypnotic, appetite-promoting, and sedative side effects. Most second-generation antipsychotics have potent antagonistic effects on histamine H1 receptor (H1R). Positron emission tomography (PET) can measure the H1R occupancy (H1RO) in vivo, although there are no reports regarding antipsychotics.

OBJECTIVES

We studied the H1RO of olanzapine and quetiapine in vivo with respect to their plasma concentrations and subjective drowsiness by performing human PET imaging studies with [(11)C]doxepin, a potent PET ligand of H1R.

METHODS

Six healthy Japanese male volunteers were enrolled. Cross-randomized PET imaging was performed after a single oral administration of olanzapine (2.5 mg), quetiapine (25 mg), or placebo. PET data were analyzed by region of interest and voxel-by-voxel analysis. We concurrently measured plasma drug concentrations by liquid chromatography/tandem mass spectrometry and evaluated subjective sleepiness.

RESULTS

The binding potential ratios of olanzapine and quetiapine in the cerebral cortex were significantly lower than that of the placebo. The H1RO values of olanzapine and quetiapine in the cortex were approximately 61-80 and 56-81%, respectively. The binding potential ratios of the drugs were significantly lower than that of the placebo in the dorsolateral prefrontal and lateral temporal cortices, and anterior and posterior cingulate gyri. The H1RO values in the cortex were significantly correlated with subjective sleepiness but not plasma drug concentrations.

CONCLUSIONS

Olanzapine and quetiapine have high H1RO values in the human brain under their clinical minimum doses. This study provides a foundation of the properties by which new-generation antipsychotics block the central histaminergic system in humans.

The dopamine stabilizer (-)-OSU6162 occupies a subpopulation of striatal dopamine D2/D3 receptors: an [(11)C]raclopride PET study in healthy human subjects

(-)-OSU6162 is a dopamine stabilizer that can counteract both hyperdopaminergic and hypodopaminergic states. In this study, D2/D3 receptor occupancy of (-)-OSU6162 in the human brain was investigated using positron emission tomography (PET). Twelve male healthy volunteers underwent [(11)C]raclopride PET scanning before and 1 h after a single oral dose of (-)-OSU6162 (15-90 mg). Blood samples for determination of (-)-OSU6162 and prolactin plasma levels were collected at Tmax. Parametric images of [(11)C]raclopride binding potential relative to nondisplaceable tissue (cerebellar grey matter) uptake (BPND) at baseline and after (-)-OSU6162 administration were generated using the simplified reference tissue model. MRI-based regions of interest were defined for the striatum, composed of caudate nucleus and putamen, and projected onto the co-registered parametric [(11)C]raclopride BPND image. Furthermore, three striatal subregions, ie, anterior dorsal caudate, anterior dorsal putamen, and ventral striatum, were defined manually and additionally analyzed. Plasma concentrations of (-)-OSU6162, ranging from 0.01 to 0.9 μM, showed a linear relationship with prolactin levels, reflecting blockade of pituitary D2 receptors. A concentration-dependent increase in striatal D2/D3 receptor occupancy was observed, reaching a value of about 20% at an (-)-OSU6162 plasma level of 0.2 μM, and which for higher concentrations leveled off to a maximal occupancy of about 40%. Findings were similar in the striatal subregions. The present data corroborate the notion that (-)-OSU6162 binds preferentially to a subpopulation of D2/D3 receptors, possibly predominantly extrasynaptic, and this may form the basis for the dopamine-stabilizing properties of (-)-OSU6162.

Neocortical serotonin2A receptor binding predicts quetiapine associated weight gain in antipsychotic-naive first-episode schizophrenia patients

Antipsychotic-induced weight gain is of major clinical importance since it is associated with severe metabolic complications and increased mortality. The serotonin2A receptor system has been suggested to be implicated in weight gain and obesity. However, no previous in vivo imaging data have related serotonin2A receptor binding to weight gain before and after antipsychotic monotherapy. Fifteen antipsychotic-naive first-episode schizophrenia patients were included and investigated before and after six months of quetiapine treatment. We examined the relationship between serotonin2A receptor binding as measured with positron emission tomography (PET) and [18F]altanserin and change in body mass index (BMI). Quetiapine was chosen because it is characterized by a moderately high affinity for the serotonin2A receptor and a fast dissociation rate from the dopamine D2 receptor. At baseline the mean BMI was 24.2 kg/m2, range 18-36 kg/m2. After six months of quetiapine treatment (mean dose: 383 mg/day) the BMI had, on average, increased by 6.7%, corresponding to an average weight gain of 5.0 kg. We found a significant positive correlation both between neocortical serotonin2A receptor binding prior to treatment and subsequent increase in BMI (rho=0.59, p=0.022). At follow-up, the serotonin2A receptor occupancy was positively correlated with BMI increase (rho=0.54, p=0.038). To our knowledge, these are the first in vivo receptor imaging data in initially antipsychotic-naive first-episode schizophrenia patients to show that the cerebral serotonin2A receptor is associated with antipsychotic-induced weight gain.

Active metabolites as antidepressant drugs: the role of norquetiapine in the mechanism of action of quetiapine in the treatment of mood disorders

Active metabolites of some antipsychotic drugs exhibit pharmacodynamic and pharmacokinetic properties that may be similar to or differ from the original compound and that can be translated by a different profile of responses and interactions to clinical level. Some of these antipsychotics' active metabolites might participate in mechanisms of antidepressant activity, as m-chlorophenylpiperazine (aripiprazole), 9-OH-risperidone and norquetiapine. Norquetiapine exhibits distinct pharmacological activity from quetiapine and plays a fundamental role in its antidepressant efficacy. In this review, we analyze the differential pharmacological aspects between quetiapine and norquetiapine, both from the pharmacokinetic and pharmacodynamic perspectives (affinity for dopaminergic, noradrenegic, and/or serotonergic receptors, etc.), as well as differential neuroprotective role. The pharmacological differences between the two drugs could explain the differential clinical effect, as well as some differences in tolerability profile and drug interactions. The available data are sufficient to arrive at the conclusion that antidepressant activity of quetiapine is mediated, at least in part, by the active metabolite norquetiapine, which selectively inhibits noradrenaline reuptake, is a partial 5-HT1A receptor agonist, and acts as an antagonist at presynaptic α2, 5-HT2C, and 5-HT7 receptors.

Diverse roles of neurotensin agonists in the central nervous system

Neurotensin (NT) is a tridecapeptide that is found in the central nervous system (CNS) and the gastrointestinal tract. NT behaves as a neurotransmitter in the brain and as a hormone in the gut. Additionally, NT acts as a neuromodulator to several neurotransmitter systems including dopaminergic, sertonergic, GABAergic, glutamatergic, and cholinergic systems. Due to its association with such a wide variety of neurotransmitters, NT has been implicated in the pathophysiology of several CNS disorders such as schizophrenia, drug abuse, Parkinson's disease (PD), pain, central control of blood pressure, eating disorders, as well as, cancer and inflammation. The present review will focus on the role that NT and its analogs play in schizophrenia, endocrine function, pain, psychostimulant abuse, and PD.

Antipsychotics, dopamine D₂ receptor occupancy and clinical improvement in schizophrenia: a meta-analysis

OBJECTIVE

Treatment of schizophrenia (SCZ) was revolutionized with the development of the antipsychotic medications. Although imaging studies have linked antipsychotic D₂ receptor occupancy and clinical response in SCZ, heterogeneity between cohorts and methods has made it challenging to generalize findings across studies. The main objective of this meta-analysis was to analyze the relationship between in vivo estimation of typical and atypical antipsychotic D₂ receptor occupancy and treatment response in SCZ.

METHODS

Using the keywords "dopamine D₂ receptor occupancy," "schizophrenia," "PET/SPECT" and "antipsychotics," and further refining our search to journal articles with information on % striatal D₂ occupancy and % change in clinical symptoms as indexed by either the BPRS or the PANSS, our final analysis consisted of 16 imaging studies (20 cohorts; N=206).

RESULTS

The first step of the meta-analysis confirmed the positive relationship between antipsychotic medication and clinical improvement in SCZ (ES=1.36; 95% CI: 1.13-1.60). The second step of our analysis revealed that when D₂ occupancy was limited to less than 80% in order to control for the appearance of extrapyramidal symptoms, high D₂ occupancy was correlated with reduction in clinical scores (r=0.4, p<0.001) for medications other than clozapine or quetiapine.

CONCLUSIONS

Our results suggest that D₂ occupancy is a contributing factor for the mechanism of antipsychotic effect in SCZ for some but not all antipsychotic medications.

Frightening music triggers rapid changes in brain monoamine receptors: a pilot PET study

Frightening music can rapidly arouse emotions in listeners that mimic those from actual life-threatening experiences. However, studies of the underlying mechanism for perceiving danger created by music are limited.

METHODS

We investigated monoamine receptor changes induced by frightening music using (11)C-N-methyl-spiperone ((11)C-NMSP) PET. Ten healthy male volunteers were included, and their psychophysiologic changes were evaluated.

RESULTS

Compared with the baseline condition, listening to frightening music caused a significant decrease in (11)C-NMSP in the right and left caudate nuclei, right limbic region, and right paralimbic region; a particularly significant decrease in the right anterior cingulate cortex; but an increase in the right frontal occipital and left temporal lobes of the cerebral cortex.

CONCLUSION

Transient fright triggers rapid changes in monoamine receptors, which decrease in the limbic and paralimbic regions but increase in the cerebral cortex.

In vivo quantification of striatal dopamine D2 receptor occupancy by JNJ-37822681 using [11C]raclopride and positron emission tomography

JNJ-37822681 is a novel, fast-dissociating dopamine D(2) receptor antagonist, currently in development as an antipsychotic drug candidate. A previous first-in-human study demonstrated mild central nervous system effects of JNJ-37822681 in healthy male volunteers. Significant but transient serum prolactin elevations were demonstrated, whereas other neurophysiological effects were relatively small. To investigate striatal dopamine D(2) receptor occupancy by variable single doses of JNJ-37822681, an open-label [(11)C]raclopride positron emission tomography study was performed in 12 healthy male volunteers, using the simplified reference tissue model with cerebellum as reference tissue. Oral administration of JNJ-37822681 resulted in dose-dependent dopamine D(2) receptor occupancy. Receptor occupancy increased from 9-19% at 2 mg doses to 60-74% at 20 mg doses of JNJ-37822681. Therefore, single oral doses of JNJ-37822681 can produce occupancy levels that are generally associated with clinical efficacy for registered antipsychotic drugs.

Quetiapine: a review of its use in the management of bipolar depression

Quetiapine (Seroquel®) is an orally administered atypical antipsychotic that is indicated for the treatment of schizophrenia and bipolar disorder, including bipolar depression. An extended-release (XR) formulation of quetiapine is also available. This review summarizes the pharmacological properties, efficacy and tolerability of quetiapine and quetiapine XR in patients with bipolar depression. Quetiapine is an antagonist at both serotonin 5-HT2 and dopamine D2 receptors, and its antipsychotic effects are thought to stem from interactions at these receptors. The antidepressant effects of quetiapine are poorly understood, but may be related to antagonism of 5-HT2A receptors in cortical regions, partial agonism of 5-HT1A in the prefrontal cortex in association with increased extracellular dopamine release in the region, or to reduced synaptic reuptake of noradrenaline resulting from inhibition of the noradrenaline reuptake transporter by the quetiapine metabolite norquetiapine. The efficacy and tolerability of quetiapine was evaluated in five 8-week, randomized, double-blind, placebo-controlled, multicentre or multinational trials in patients with a major depressive episode (MDE) associated with bipolar disorder. Across trials, monotherapy with oral quetiapine 300 or 600 mg/day (or quetiapine XR 300 mg/day) produced significantly greater improvements than placebo in depressive symptoms (primary endpoint), according to the change in the Montgomery-Asberg Depression Rating Scale total score. In general, quetiapine and quetiapine XR were also associated with significantly higher MDE response and remission rates than placebo. Across trials, quetiapine and quetiapine XR produced significantly greater improvements in global severity of illness scores than placebo, according to changes in the Clinical Global Impressions scale score. There were no differences in treatment outcomes between quetiapine 300 mg/day and 600 mg/day dosage groups. Patients with bipolar depression who responded to quetiapine during two 8-week acute treatment trials also benefited from continuing quetiapine therapy for up to 52 weeks. Compared with quetiapine responders randomized to placebo, quetiapine responders who continued quetiapine 300 or 600 mg/day had a significantly reduced risk of recurrence of any mood events and of depression mood events, but not of hypomanic/manic events. In a randomized, double-blind, placebo-controlled trial, quetiapine maintenance therapy for up to 104 weeks was more efficacious than placebo or lithium in prolonging the time to recurrence of any mood event (primary endpoint). Patients in this trial had bipolar I disorder with mania, depression or a mixed episode as the index episode, and the trial included only patients who were responsive to acute phase quetiapine, which may have introduced a positive bias in favour of quetiapine over lithium during maintenance therapy. Quetiapine 300 or 600 mg/day and quetiapine XR 300 mg/day was generally well tolerated in patients with bipolar depression, with most treatment-emergent adverse events being of mild to moderate severity. The most frequent adverse events occurring during the acute treatment phase were dry mouth, sedation, somnolence, dizziness (quetiapine and quetiapine XR), constipation (quetiapine) and increased appetite (quetiapine XR). Extrapyramidal symptoms (EPS) occurred across quetiapine and placebo groups, but there were no significant differences between quetiapine and placebo recipients on objective measures of EPS and akathisia. In some trials, quetiapine recipients experienced significantly greater weight gain than placebo recipients. Across trials, some quetiapine recipients had clinically relevant increases in blood glucose or lipid parameters, although these also occurred in patients from other treatment groups. The clinical significance of these changes is uncertain. In conclusion, quetiapine and quetiapine XR are valuable additions to the first-line treatments for bipolar depression. Further head-to-head trials of quetiapine versus other drug regimens that are effective in bipolar depression would be of considerable interest.

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.

A double-blind, randomized, controlled trial of fluoxetine plus quetiapine or clomipramine versus fluoxetine plus placebo for obsessive-compulsive disorder

Obsessive-compulsive disorder patients who do not improve sufficiently after treatment with a selective serotonin reuptake inhibitor might improve further if other drugs were added to the treatment regimen. The authors present a double-blind, placebo-controlled trial comparing the efficacy of adding quetiapine or clomipramine to a treatment regimen consisting of fluoxetine. Between May 2007 and March 2010, a total of 54 patients with a primary diagnosis of obsessive-compulsive disorder, as defined by Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, and a current Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) score of at least 16, the score having dropped by less than 35% after fluoxetine monotherapy, were allocated to 1 of 3 arms (n = 18 per arm): quetiapine + fluoxetine (≤200 and ≤40 mg/d, respectively), clomipramine + fluoxetine (≤75 and ≤40 mg/d, respectively), or placebo + fluoxetine (≤80 mg/d of fluoxetine). Follow-up was 12 weeks. The Y-BOCS scores were the main outcome measure. No severe adverse events occurred during the trial, and 40 patients (74%) completed the 12-week protocol. The Y-BOCS scores (mean [SD]) were significantly better in the placebo + fluoxetine and clomipramine + fluoxetine groups than in the quetiapine + fluoxetine group (final: 18 [7] and 18 [7], respectively, vs 25 [6], P < 0.001) (reduction from baseline: -6.7 [confidence interval {CI}, -9.6 to -3.8; and -6.5 [CI, -9.0 to -3.9], respectively, vs -0.1 [CI, -2.9 to 2.7], P < 0.001; number needed to treat = 2.4). The clomipramine-fluoxetine combination is a safe and effective treatment for fluoxetine nonresponders, especially those who cannot tolerate high doses of fluoxetine. However, the period of monotherapy with the maximum dose of fluoxetine should be extended before a combination treatment strategy is applied.

Drug-induced sleep: theoretical and practical considerations

Faithful replication of normal sleep through medications--can it be achieved? Departure from normal sleep with the use of drugs--when is it desired? Answers to these questions depend on accurate understanding of sleep and on concrete criteria upon which to define it. Since these elements are evolving sciences, as yet incompletely known, one might take a nihilistic approach that we simply cannot judge whether we have successfully replicated sleep, since we do not fully grasp what sleep is or what it does. To address these potential obstacles, our article is written in two sections. The first addresses theoretical considerations for how medications might be seen in the larger framework of sleep. The purpose of this section is to inform readers about key issues in evaluating whether a drug has sufficient data to persuasively argue it is re-creating sleep. (We hope that researchers interested in conducting studies, or critical readers of the drug-study literature, might find this section particularly useful.) The second section of this article approaches exemplary, current concepts of pharmacologic manipulation of sleep, organized by disorders as articulated by the International Classification of Sleep Disorders (2005). This second section will combine practical knowledge of clinical sleep medicine, with emphasis on contemporary knowledge about molecular mechanisms that are felt to underlie some of these phenomena. We recognize that our collective knowledge about sleep will advance in the coming years. We hope that this article serves to facilitate that advance.

Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part II

Rapid-onset psychotic rebound is uncommon on discontinuation of most antipsychotic drugs, as might be expected for antipsychotic drugs with (hypothetically) indirect actions at their final target receptors. Rapid-onset psychosis is more common on withdrawal of clozapine, which might be expected if its action is direct. Drugs other than clozapine (notably thioridazine) may have hitherto unrecognised similarities to clozapine (but without danger of agranulocytosis), and may be useful in treatment of refractory psychosis. Quetiapine fulfils only some criteria for a clozapine-like drug. Clinical response to neuroleptics varies widely at any given plasma level. Haase's "neuroleptic threshold" concept suggests that the dose producing the slightest motor side effects produces most or all of the therapeutic benefit, but analyses presented here suggest that antipsychotic actions are not subject to a sharp "all-or-none" threshold but increase over a small dose range. This concept could provide a method for quantitative determination of individualized optimal doses.

Serotonin2A receptor blockade and clinical effect in first-episode schizophrenia patients treated with quetiapine

RATIONALE

We have previously reported decreased frontal cortical serotonin2A receptor binding in 30 antipsychotic naïve first-episode schizophrenic patients and a relationship between this binding and positive psychotic symptoms. Until now, no longitudinal studies of serotonin2A receptor in first-episode antipsychotic-naïve schizophrenia patients have reported on the relationship between serotonin2A receptor occupancy and treatment effect after sustained treatment with a specific atypical antipsychotic compound.

OBJECTIVES

Here, we measured serotonin2A receptor occupancy with [(18)F]altanserin PET in 15 first-episode antipsychotic-naïve schizophrenia patients before and after 6 months of quetiapine treatment. Moreover, we investigated possible relationships between clinical efficacy, oral dose, and plasma levels of quetiapine

RESULTS

Significant nonlinear relationships were found between serotonin2A receptor occupancy, quetiapine dose, and plasma concentration. There was a modest effect on positive symptoms up until a serotonin2A receptor occupancy level of approximately 60%. A receptor occupancy level between 60% and 70% appeared to exert the optimal serotonin2A receptor related treatment effect on positive symptoms whereas no additional serotonin2A receptor associated treatment effect was obtained above a receptor occupancy of 70%.

CONCLUSIONS

Taken together, the data point to a therapeutic role of the serotonin2A receptor in the treatment of subgroups of patients with schizophrenia. Specifically, the study indicates a serotonin2A receptor associated therapeutic window on positive symptoms in responding patients in the range between 60% and 70% occupancy in antipsychotic-naïve first-episode schizophrenia. We speculate that non-responding patients need higher dopamine D(2) receptor blockade. Future studies with concurrent measurement of interactions with the dopamine system are, however, warranted to clarify this.

Progressive striatal and hippocampal volume loss in initially antipsychotic-naive, first-episode schizophrenia patients treated with quetiapine: relationship to dose and symptoms

First-generation antipsychotics have been associated with striatal volume increases. The effects of second-generation antipsychotics (SGAs) on the striatum are unclear. Moreover, SGAs may have neuroprotective effects on the hippocampus. Dose-dependent volumetric effects of individual SGAs have scarcely been investigated. Here we investigated structural brain changes in antipsychotic-naive, first-episode schizophrenia patients after 6 months treatment with the SGA, quetiapine. We have recently reported on baseline volume reductions in the caudate nucleus and hippocampus. Baseline and follow-up T1-weighted images (3 T) from 22 patients and 28 matched healthy controls were analysed using tensor-based morphometry. Non-parametric voxel-wise group comparisons were performed. Small volume correction was employed for striatum, hippocampus and ventricles. Dose-dependent medication effects and associations with psychopathology were assessed. Patients had significant bilateral striatal and hippocampal loss over the 6-month treatment period. When compared to controls the striatal volume loss was most pronounced with low quetiapine doses and less apparent with high doses. Post-hoc analyses revealed that the striatal volume loss was most pronounced in the caudate and putamen, but not in accumbens. Conversely, hippocampal volume loss appeared more pronounced with high quetiapine doses than with low doses. Clinically, higher baseline positive symptoms were associated with more striatal and hippocampal loss over time. Although patients' ventricles did not change significantly, ventricular increases correlated with less improvement of negative symptoms. Progressive regional volume loss in quetiapine-treated, first-episode schizophrenia patients may be dose-dependent and clinically relevant. The mechanisms underlying progressive brain changes, specific antipsychotic compounds and clinical symptoms warrant further research.

Dopamine D2 occupancy as a biomarker for antipsychotics: quantifying the relationship with efficacy and extrapyramidal symptoms

For currently available antipsychotic drugs, blockade of dopamine D(2) receptors is a critical component for achieving antipsychotic efficacy, but it is also a driving factor in the development of extrapyramidal symptoms (EPS). To inform the clinical development of asenapine, generic mathematical models have been developed for predicting antipsychotic efficacy and EPS tolerability based on D(2) receptor occupancy. Clinical data on pharmacokinetics, D(2) receptor occupancy, efficacy, and EPS for several antipsychotics were collected from the public domain. Asenapine data were obtained from in-house trials. D(2) receptor occupancy data were restricted to published positron emission tomography studies that included blood sampling for pharmacokinetics. Clinical efficacy data were restricted to group mean endpoint data from short-term placebo-controlled trials, whereas EPS evaluation also included some non-placebo-controlled trials. A generally applicable model connecting antipsychotic dose, pharmacokinetics, D(2) receptor occupancy, Positive and Negative Syndrome Scale (PANSS) response, and effect on Simpson-Angus Scale (SAS) was then developed. The empirical models describing the D(2)-PANSS and D(2)-SAS relationships were used successfully to aid dose selection for asenapine phase II and III trials. A broader use can be envisaged as a dose selection tool for new antipsychotics with D(2) antagonist properties in the treatment of schizophrenia.

Antipsychotic occupancy of dopamine receptors in schizophrenia

Antipsychotic drugs were introduced in the early 50s on the basis of clinical observations in patients with schizophrenia. Experimental studies later revealed that antagonism at the D(2) dopamine receptor is a common characteristic of all antipsychotic drugs. In the 80s, the advent of brain imaging technologies such as positron emission tomography (PET) allowed for direct noninvasive studies of drug binding in treated patients. The concept receptor occupancy is defined as the fraction (%) of a receptor population that is occupied during treatment with an unlabelled drug. With regard to antipsychotic drugs, the radioligand [(11) C]-raclopride has been the most widely used for binding to the D(2) /D(3) -dopamine receptors. The present review discusses the contribution from molecular imaging to the current understanding of mechanism of action (MoA) of antipsychotic drugs. Consistent initial PET-findings of high D2-receptor occupancy in the striatum of patients responding to different antipsychotic drug treatments provided clinical support for the dopamine hypothesis of antipsychotic drug action. It has subsequently been demonstrated that patients with extrapyramidal syndromes (EPS) have higher occupancy (above 80%) than patients with good response but no EPS (65-80%). The PET-defined interval for optimal antipsychotic drug treatment has been implemented in the evolvement of dose recommendations for classical as well as more recently developed drugs. Another consistent finding is lower D(2) -occupancy during treatment with the prototype atypical antipsychotic clozapine. The MoA of clozapine remains to be fully understood and may include nondopaminergic mechanisms. A general limitation is that currently available PET-radioligands are not selective for any of the five dopamine receptor subtypes. Current attempts at developing such ligands may provide the tools required to refine further the MoA of antipsychotic drugs.

Dopamine D2/3 receptor occupancy by quetiapine in striatal and extrastriatal areas

Quetiapine is next to clozapine an antipsychotic agent that exerts hardly any extrapyramidal side-effects at clinical efficacious doses. Some previous receptor occupancy studies reported preferential extrastriatal D2/3 receptor (D2/3R)-binding properties of second-generation antipsychotics and suggested this as possible reason for improved tolerability. This positron emission tomography (PET) investigation was designed to compare the occupancy of dopamine D2/3Rs by quetiapine in striatal and extrastriatal brain regions. Therefore, a cohort of 16 quetiapine-treated psychotic patients underwent an [18F]fallypride (FP) PET scan. Due to the high affinity of FP and its comparatively long half-life, striatal and extrastriatal binding potentials could be determined in one single scan. Receptor occupancy was calculated as percent reduction in binding potential relative to age-matched medication-free patients suffering from schizophrenia. Quetiapine occupied 44+/-18% in the temporal cortex and 26+/-17% in the putamen, a difference significant at the level of p=0.005 (Student's t test). Quetiapine showed a mean occupancy of 36+/-16% and in the thalamus. In the caudate nucleus there was an occupancy of 29+/-16% (p=0.0072). Individual occupancy levels did not exceed 59% in any of the striatal volumes of interest. The time-interval between scan and last drug ingestion did not influence the relationship between plasma concentration and central D2/3R occupancy. Taken together, quetiapine shows preferential extrastriatal binding at D2/3Rs; the extent of this difference is comparable to that previously described for clozapine. Both antipsychotics show very low affinity for D2/3Rs.

Positron emission tomography in schizophrenia: a new perspective

PET is an important functional imaging technique that can be used to investigate neurotransmitter receptors and transporters directly by mapping human brain function. PET is increasingly being used greatly to advance our understanding of the neurobiology and pathophysiology of schizophrenia.

METHODS

This review focuses on the use of PET tracers and kinetic modeling in identifying regional brain abnormalities and regions associated with cognitive functioning in schizophrenia. A variety of PET tracers have been used to identify brain abnormalities, including (11)C, (15)O-water, (18)F-fallypride, and L-3,4-dihydroxy-6-(18)F-fluorophenylalanine ((18)F-FDOPA).

RESULTS

Some studies have used compartmental modeling to determine tracer binding kinetics. The most consistent findings show a difference in the dopamine content in the prefrontal cortex, anterior cingulate gyrus, and hippocampus between healthy controls and patients with schizophrenia. Studies also show a higher density of D(2) receptors in the striatum and neural brain dysconnectivity.

CONCLUSION

Future investigations integrating clinical, imaging, genetic, and cognitive aspects are warranted to gain a better understanding of the pathophysiology of this disorder.

Quetiapine versus clomipramine in the augmentation of selective serotonin reuptake inhibitors for the treatment of obsessive-compulsive disorder: a randomized, open-label trial

After 12 weeks of selective serotonin reuptake inhibitor (SSRI) monotherapy with inadequate response, 10 patients received clomipramine and 11 received quetiapine as augmentation agents of the SSRI. The primary outcome measure was the difference between initial and final scores of the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), rated in a blinded fashion, and the score of clinical global improvement (CGI-I). Statistical analyses were performed using nonparametric tests to evaluate treatment efficacy and the difference between treatment groups. Percentile plots were constructed with YBOCS scores from the clomipramine and quetiapine groups. Considering response a >or=35% reduction in the initial Y-BOCS score plus a rating of 'much improved' or 'very much improved' on CGI-I, four of eleven quetiapine patients and one out of ten clomipramine patients were classified as responders. The mean final Y-BOCS score was significantly lower than baseline in the quetiapine augmentation group (P = 0.023), but not in the clomipramine augmentation group (P = 0.503). The difference between groups showed a trend towards significance only at week 4, the mean Y-BOCS score being lower for those receiving quetiapine (P = 0.052). A difference between groups was also observed at week 4 according to percentile plots. These results corroborate previous findings of quetiapine augmentation efficacy in obsessive-compulsive disorder (OCD). Clomipramine augmentation did not produce a significant reduction in Y-BOCS scores. Higher target maximum dosages might have yielded different results.

Low-dose quetiapine for patients with dysregulation of hyperthymic and cyclothymic temperaments

Patients with hyperthymic and cyclothymic temperaments often develop symptoms that fail to meet diagnostic criteria for bipolar disorders. These patients can be conceived as having bipolar disorder NOS (not otherwise specified), a bipolar spectrum disorder, cyclothymic disorder or cluster B personality traits. Here, we describe four of these patients with mild to moderate symptoms affecting mood, behaviour, emotional reactivity and sleep. Treatment with low-dose quetiapine (25-75 mg/day at night) lead to sustained symptom remission. Two of them were on quetiapine monotherapy. Such low doses occupy a minority of D2 and 5-HT2 receptors, which may nevertheless be of therapeutic value in mild cases. Alternatively, other mechanisms more likely to occur at low doses, such as antagonism of H1, alpha(1B)-adrenergic and other serotonin receptors, as well as reduction cortisol secretion, may be involved in the therapeutic efficacy of quetiapine.

Signs of striatal dopamine transporter density increase in association with improvement of tardive dyskinesia in a patient with schizophrenia, as demonstrated by a DAT scan

The imaging of the dopamine transporter could demonstrate the implication of dopaminergic pathway in the appearance of tardive dyskinesia. We report a case with psychotic and tardive dyskinesia symptoms. A DAT scan showed decreased dopamine transporter uptake in the area of brain's basal gaglia. A trial with quetiapine improved both psychotic and TD symptoms while a second DAT scan showed improvement status. We conclude that increased dopamine transporter uptake seemed to associate with the improvement of TD.

Mechanisms underlying psychosis and antipsychotic treatment response in schizophrenia: insights from PET and SPECT imaging

Molecular imaging studies have generated important in vivo insights into the etiology of schizophrenia and treatment response. This article first reviews the PET and SPECT evidence implicating dopaminergic dysfunction, especially presynaptic dysregulation, as a mechanism for psychosis. Second, it summarises the neurochemical imaging studies of antipsychotic action, focussing on D2/3 receptors. These studies show that all currently licensed antipsychotic drugs block striatal D2/3 receptors in vivo- a site downstream of the likely principal dopaminergic pathophysiology in schizophrenia- and that D2/3 occupancy above a threshold is required for antipsychotic treatment response. However, adverse events, such as extra-pyramidal side-effects or hyperprolactinemia, become much more likely at higher occupancy levels, which indicates there is an optimal 'therapeutic window' for D2/3 occupancy, and questions the use of high doses of antipsychotic treatment in clinical practice and trials. Adequate D2/3 blockade by antipsychotic drugs is necessary but not always sufficient for antipsychotic response. Molecular imaging studies of clozapine, the one antipsychotic licensed for treatment resistant schizophrenia, have provided insights into the mechanisms underlying its unique efficacy. To link this pharmacology to the phenomenology of the illness, we discuss the role of dopamine in motivational salience and show how i) psychosis could be viewed as a process of aberrant salience, and ii) antipsychotics might provide symptomatic relief by blocking this aberrant salience. Finally, we discuss the implications of these PET and SPECT findings for new avenues of drug development.

Tardive dyskinesia in a patient treated with quetiapine

Quetiapine is an atypical antipsychotic that is believed to have a low D2 binding affinity in striatal and extrastriatal regions. We report the case of a female patient with the diagnosis of schizoaffective disorder (using DSM-IV-TR criteria) who initially received amisulpride for 3 months, discontinued gradually because of persistent and distressing extra-pyramidal symptoms, and who developed tardive dyskinesia 3 months later after the initiation of quetiapine. A trial with ziprasidone resulted in a further worsening of tardive dyskinesia symptoms. A further trial with aripiprazole, improved her tardive dyskinesia symptoms. Although, it is under consideration the possibility that the improvement could have been due to the discontinuation of quetiapine, we conclude that aripiprazole improved the TD symptoms.

Cortical dopamine D2/D3 receptors are a common site of action for antipsychotic drugs--an original patient data meta-analysis of the SPECT and PET in vivo receptor imaging literature

Subject numbers in neuroreceptor imaging studies of antipsychotic treatment in schizophrenia are generally insufficient to directly test the relationship of regional D(2)/D(3) and 5HT(2A) receptor binding to clinical efficacy. We selected positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies of antipsychotic dose vs occupancy at both temporal cortex and striatal D(2)/D(3) receptors. We selected corresponding SPECT and PET studies of 5HT(2A) receptor occupancy. We also selected randomized double-blind clinical trials of antipsychotics, where patients were treated with randomly assigned fixed doses. For each antipsychotic drug, we compared the optimum effective antipsychotic dose with the dose inducing maximal occupancy of D(2)/D(3) receptors in striatum and in temporal cortex as well as at 5HT(2A) receptors. Both first- and second-generation antipsychotic (FGA, SGA) drugs produced high temporal cortex D(2)/D(3) occupancy. Only FGA produced high striatal D(2)/D(3) receptor occupancy. The clinically effective dose showed correlation with doses inducing maximal dopamine D(2)/D(3) receptor occupancy both in striatum and in temporal cortex, the strongest correlation being with temporal cortex binding. Extrapyramidal side effects (EPSE) were primarily related to striatal D(2)/D(3) receptor occupancy. There was no correlation between 5HT(2A) occupancy and clinically effective dose. We conclude that cortical dopamine D(2)/D(3) receptor occupancy is involved in antipsychotic efficacy, with striatal D(2)/D(3) occupancy having a likely therapeutic role while also inducing EPSE. We found no evidence for 5HT(2A) blockade involvement in antipsychotic action, although we cannot exclude this possibility.