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Nikolaus S, Mamlins E, Hautzel H, Müller HW. Acute anxiety disorder, major depressive disorder, bipolar disorder and schizophrenia are related to different patterns of nigrostriatal and mesolimbic dopamine dysfunction. Rev Neurosci 2019; 30:381-426. [PMID: 30269107 DOI: 10.1515/revneuro-2018-0037] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 06/30/2018] [Indexed: 11/15/2022]
Abstract
Dopamine (DA) receptor and transporter dysfunctions play a major role in the pathophysiology of neuropsychiatric diseases including anxiety disorder (AD), major depressive disorder (MDD), bipolar disorder (BD) in the manic (BDman) or depressive (BDdep) state and schizophrenia (SZ). We performed a PUBMED search, which provided a total of 239 in vivo imaging studies with either positron emission tomography (PET) or single-proton emission computed tomography (SPECT). In these studies, DA transporter binding, D1 receptor (R) binding, D2R binding, DA synthesis and/or DA release in patients with the primary diagnosis of acute AD (n=310), MDD (n=754), BDman (n=15), BDdep (n=49) or SZ (n=1532) were compared to healthy individuals. A retrospective analysis revealed that AD, MDD, BDman, BDdep and SZ differed as to affected brain region(s), affected synaptic constituent(s) and extent as well as direction of dysfunction in terms of either sensitization or desensitization of transporter and/or receptor binding sites. In contrast to AD and SZ, in MDD, BDman and BDdep, neostriatal DA function was normal, whereas MDD, BDman, and BDdep were characterized by the increased availability of prefrontal and frontal DA. In contrast to AD, MDD, BDman and BDdep, DA function in SZ was impaired throughout the nigrostriatal and mesolimbocortical system with an increased availability of DA in the striatothalamocortical and a decreased availability in the mesolimbocortical pathway.
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Affiliation(s)
- Susanne Nikolaus
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Eduards Mamlins
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Hubertus Hautzel
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Hans-Wilhelm Müller
- Clinic of Nuclear Medicine, University Hospital Düsseldorf, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
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Nakajima S, Uchida H, Bies RR, Caravaggio F, Suzuki T, Plitman E, Mar W, Gerretsen P, Pollock BG, Mulsant BH, Mamo DC, Graff-Guerrero A. Dopamine D2/3 Receptor Occupancy Following Dose Reduction Is Predictable With Minimal Plasma Antipsychotic Concentrations: An Open-Label Clinical Trial. Schizophr Bull 2016. [PMID: 26221049 PMCID: PMC4681559 DOI: 10.1093/schbul/sbv106] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Population pharmacokinetics can predict antipsychotic blood concentrations at a given time point prior to a dosage change. Those predicted blood concentrations could be used to estimate the corresponding dopamine D2/3 receptors (D2/3R) occupancy by antipsychotics based on the tight relationship between blood and brain pharmacokinetics. However, this 2-step prediction has never been tested. METHODS Two blood samples were collected at separate time points from 32 clinically stable outpatients with schizophrenia (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; mean ± SD age: 60.1 ± 7.3 years) to measure plasma concentrations of olanzapine or risperidone at baseline. Then, subjects underwent a dose reduction of olanzapine or risperidone and completed a [(11)C]-raclopride positron emission tomography scan to measure D2/3R occupancy in the putamen. The plasma concentration at the time of the scan was predicted with the 2 samples based on population pharmacokinetic model, using NONMEM. D2/3R occupancy was then estimated by incorporating the predicted plasma concentration in a hyperbole saturation model. The predicted occupancy was compared to the observed value. RESULTS The mean (95% CI) prediction errors for the prediction of D2/3R occupancy were -1.76% (-5.11 to 1.58) for olanzapine and 0.64% (-6.18 to 7.46) for risperidone. The observed and predicted D2/3R occupancy levels were highly correlated (r = 0.67, P = .001 for olanzapine; r = 0.67, P = .02 for risperidone). CONCLUSIONS D2/3R occupancy levels can be predicted from blood drug concentrations collected prior to dosage change. Although this 2-step model is subject to a small degree of error, it could be used to select oral doses aimed at achieving optimal D2/3R occupancy on an individual basis.
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Affiliation(s)
| | - Hiroyuki Uchida
- Geriatric Mental Health Division, Centre for Addiction and Mental Health, Toronto, Canada; Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan;
| | - Robert R. Bies
- Geriatric Mental Health Division, Centre for Addiction and Mental Health, Toronto, Canada;,Indiana University School of Medicine, Division of Clinical Pharmacology, Indianapolis, IN
| | - Fernando Caravaggio
- Multimodal Imaging Group - Research Imaging Centre and,Department of Psychiatry, University of Toronto, Toronto, Canada;,Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Takefumi Suzuki
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Eric Plitman
- Multimodal Imaging Group - Research Imaging Centre and,Department of Psychiatry, University of Toronto, Toronto, Canada;,Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Wanna Mar
- Multimodal Imaging Group - Research Imaging Centre and
| | - Philip Gerretsen
- Department of Psychiatry, University of Toronto, Toronto, Canada
| | - Bruce G. Pollock
- Geriatric Mental Health Division, Centre for Addiction and Mental Health, Toronto, Canada;,Department of Psychiatry, University of Toronto, Toronto, Canada;,Campbell Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
| | - Benoit H. Mulsant
- Geriatric Mental Health Division, Centre for Addiction and Mental Health, Toronto, Canada;,Department of Psychiatry, University of Toronto, Toronto, Canada;,Campbell Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
| | - David C. Mamo
- Department of Psychiatry, University of Toronto, Toronto, Canada
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Therapeutic window for striatal dopamine D(2/3) receptor occupancy in older patients with schizophrenia: a pilot PET study. Am J Geriatr Psychiatry 2014; 22:1007-16. [PMID: 25217025 DOI: 10.1016/j.jagp.2013.01.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Revised: 01/21/2012] [Accepted: 02/27/2012] [Indexed: 11/23/2022]
Abstract
OBJECTIVE In younger patients with schizophrenia, positron emission tomography (PET) studies have identified a therapeutic window of striatal dopamine D(2/3) receptor occupancy of 65%-80%. This type of empirical information is not available in late life. Our primary aim was to assess the effect of changes in D(2/3) relative receptor occupancy (RRO) on clinical outcomes in this population. DESIGN Open-label intervention. SETTING Centre for Addiction and Mental Health, Toronto. PARTICIPANTS Subjects with schizophrenia age 50 years or more who were clinically stable and previously maintained on oral risperidone for D(2/3) RRO in dorsal putamen was assessed, using the region of interest analysis of [¹¹C]raclopride PET scans, before and after the dose reduction. Clinical assessments included the Positive and Negative Syndrome Scale and the Simpson-Angus Scale. RESULTS Nine subjects (mean ± SD age: 58 ± 7 years; mean ± SD baseline risperidone dose: 3.4 ± 1.6 mg/day) participated in the study. Extrapyramidal symptoms (EPS) were present in six subjects and were associated with 70% or more D(2/3) RRO in the putamen (range: 70%-87%). Following the dose reduction, EPS resolved in five subjects. Two subjects experienced a clinical worsening at 52% and at less than 50% D(2/3) RRO. CONCLUSION EPS diminished less than 70% D(2/3) RRO, which suggests a lower therapeutic window for older patients with schizophrenia than that for younger patients. Although these findings have to be replicated in a larger sample, they have important implications for future drug development and clinical guidelines in late-life schizophrenia.
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Vyas NS, Patel NH, Nijran KS, Al-Nahhas A, Puri BK. The use of PET imaging in studying cognition, genetics and pharmacotherapeutic interventions in schizophrenia. Expert Rev Neurother 2014; 11:37-51. [DOI: 10.1586/ern.10.160] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Dopamine D₂/₃ occupancy of ziprasidone across a day: a within-subject PET study. Psychopharmacology (Berl) 2013; 228:43-51. [PMID: 23417515 PMCID: PMC3679209 DOI: 10.1007/s00213-013-3012-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Accepted: 01/24/2013] [Indexed: 10/27/2022]
Abstract
RATIONALE Ziprasidone is an atypical antipsychotic recommended to be administered twice daily. OBJECTIVES The purpose of this study was to investigate whether occupancy of the dopamine D2/3 receptors by ziprasidone is maintained across a day employing a within subject design. METHODS Positron emission tomography (PET) scans with [(11)C]-raclopride were performed in 12 patients with schizophrenia while treated with ziprasidone 60 mg twice daily. Each patient completed [(11)C]-raclopride PET scans at 5, 13 and 23 h after the last dose of ziprasidone. Dopamine D2/3 receptor occupancy was estimated with reference to binding potential data of 44 age- and sex-matched control subjects in the caudate, putamen and ventral striatum. RESULTS Eleven scans were available at each time point, and the mean occupancies at 5-, 13- and 23-h scans were 66, 39 and 2 % in the putamen; 62, 35 and -6 % in the caudate; and 68, 47 and 11 % in the ventral striatum, respectively. The time-course of receptor occupancy across the regions indicated an occupancy half-life of 8.3 h. The serum level of ziprasidone associated with 50 % D2/3 receptors occupancy was estimated to be 204 nmol/L (84 ng/ml). Prolactin levels were highest at 5-h post-dose and none showed hyperprolactinemia at 23-h scans. CONCLUSIONS The absence of ziprasidone striatal D2/3 receptor binding 23 h after taking 60 mg under steady-state conditions is consistent with its peripheral half-life. The results support our earlier report that ziprasidone 60 mg administered twice daily appears to be the minimal dose expected to achieve therapeutic central dopamine D2/3 receptor occupancy (i.e. 60 %). CLINICAL TRIALS REGISTRATION 24-Hour Time Course of Striatal Dopamine D2 Receptor Occupancy of Ziprasidone: A PET Study, www.clinicaltrials.gov/ct2/show/NCT00818298 , NCT00818298.
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Bailer UF, Frank GK, Price JC, Meltzer CC, Becker C, Mathis CA, Wagner A, Barbarich-Marsteller NC, Bloss CS, Putnam K, Schork NJ, Gamst A, Kaye WH. Interaction between serotonin transporter and dopamine D2/D3 receptor radioligand measures is associated with harm avoidant symptoms in anorexia and bulimia nervosa. Psychiatry Res 2013; 211:160-8. [PMID: 23154100 PMCID: PMC3880148 DOI: 10.1016/j.pscychresns.2012.06.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 06/25/2012] [Accepted: 06/29/2012] [Indexed: 10/27/2022]
Abstract
Individuals with anorexia nervosa (AN) and bulimia nervosa (BN) have alterations of measures of serotonin (5-HT) and dopamine (DA) function, which persist after long-term recovery and are associated with elevated harm avoidance (HA), a measure of anxiety and behavioral inhibition. Based on theories that 5-HT is an aversive motivational system that may oppose a DA-related appetitive system, we explored interactions of positron emission tomography (PET) radioligand measures that reflect portions of these systems. Twenty-seven individuals recovered (REC) from eating disorders (EDs) (7 AN-BN, 11 AN, 9 BN) and nine control women (CW) were analyzed for correlations between [(11)C]McN5652 and [(11)C]raclopride binding. There was a significant positive correlation between [(11)C]McN5652 binding potential (BP(non displaceable(ND))) and [(11)C]Raclopride BP(ND) for the dorsal caudate, antero-ventral striatum (AVS), middle caudate, and ventral and dorsal putamen. No significant correlations were found in CW. [(11)C]Raclopride BP(ND), but not [(11)C]McN5652 BP(ND), was significantly related to HA in REC EDs. A linear regression analysis showed that the interaction between [(11)C]McN5652 BP(ND) and [(11)C]raclopride BP(ND) in the dorsal putamen significantly predicted HA. This is the first study using PET and the radioligands [(11)C]McN5652 and [(11)C]raclopride to show a direct relationship between 5-HT transporter and striatal DA D2/D3 receptor binding in humans, supporting the possibility that 5-HT and DA interactions contribute to HA behaviors in EDs.
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Affiliation(s)
- Ursula F. Bailer
- University of California San Diego, Department of Psychiatry, La Jolla, CA,Medical University of Vienna, Department of Psychiatry and Psychotherapy, Division of Biological Psychiatry, Vienna, Austria
| | - Guido K. Frank
- Department of Psychiatry, University of Colorado Denver, Children’s Hospital Colorado, Aurora, CO, USA,Department of Neuroscience, University of Colorado Denver; Anschutz Medical Campus, Aurora, CO, USA
| | - Julie C. Price
- University of Pittsburgh, School of Medicine, Department of Radiology, Presbyterian University Hospital, Pittsburgh, PA
| | - Carolyn C. Meltzer
- University of Pittsburgh, School of Medicine, Department of Radiology, Presbyterian University Hospital, Pittsburgh, PA,University of Pittsburgh, School of Medicine, Department of Psychiatry, Western Psychiatric Institute and Clinic, Pittsburgh, PA,Emory School of Medicine, Departments of Radiology, Neurology, and Psychiatry and Behavioral Sciences, Atlanta, Georgia, and Adjunct Professor of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Carl Becker
- University of Pittsburgh, School of Medicine, Department of Radiology, Presbyterian University Hospital, Pittsburgh, PA
| | - Chester A. Mathis
- University of Pittsburgh, School of Medicine, Department of Radiology, Presbyterian University Hospital, Pittsburgh, PA
| | - Angela Wagner
- University of California San Diego, Department of Psychiatry, La Jolla, CA
| | | | - Cinnamon S. Bloss
- Scripps Genomic Medicine, Scripps Translational Science Institute (STSI), and Scripps Health, La Jolla, CA
| | - Karen Putnam
- Department of Environmental Health, Division of Epidemiology and Biostatistics, University of Cincinnati, School of Medicine, Cincinnati, Ohio
| | - Nicholas J. Schork
- Department of Environmental Health, Division of Epidemiology and Biostatistics, University of Cincinnati, School of Medicine, Cincinnati, Ohio
| | - Anthony Gamst
- University of California San Diego, Department of Biostatistics and Bioinformatics, La Jolla, CA
| | - Walter H. Kaye
- University of California San Diego, Department of Psychiatry, La Jolla, CA,Corresponding author: Walter H. Kaye, M.D., University of California, San Diego, UCSD Department of Psychiatry, 8950 Villa La Jolla Drive, Suite C – 207, La Jolla, California 92037, Tel. (858) 534 3951, FAX: (858) 534 6727,
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Duffy AM, Fitzgerald ML, Chan J, Robinson DC, Milner TA, Mackie K, Pickel VM. Acetylcholine α7 nicotinic and dopamine D2 receptors are targeted to many of the same postsynaptic dendrites and astrocytes in the rodent prefrontal cortex. Synapse 2011; 65:1350-67. [PMID: 21858872 PMCID: PMC3356922 DOI: 10.1002/syn.20977] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The alpha-7 nicotinic acetylcholine receptor (α7nAChR) and the dopamine D(2) receptor (D(2) R) are both implicated in attentional processes and cognition, mediated in part through the prefrontal cortex (PFC). We examined the dual electron microscopic immunolabeling of α7nAChR and either D(2) R or the vesicular acetylcholine transporter (VAChT) in rodent PFC to assess convergent functional activation sites. Immunoreactivity (ir) for α7nAChR and/or D(2) R was seen in the same as well as separate neuronal and glial profiles. At least half of the dually labeled profiles were somata and dendrites, while most labeled axon terminals expressed only D(2) R-ir. The D(2) R-labeled terminals were without synaptic specializations or formed inhibitory or excitatory-type synapses with somatodendritic profiles, some of which expressed the α7nAChR and/or D(2) R. Astrocytic glial processes comprised the majority of nonsomatodendritic α7nAChR or α7nAChR and D(2) R-labeled profiles. Glial processes containing α7nAChR-ir were frequently located near VAChT-labeled terminals and also showed perisynaptic and perivascular associations. We conclude that in rodent PFC α7nACh and D(2) R activation can dually modulate (1) postsynaptic dendritic responses within the same or separate but synaptically linked neurons in which the D(2) R has the predominately presynaptic distribution, and (2) astrocytic signaling that may be crucial for synaptic transmission and functional hyperemia.
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Affiliation(s)
- Aine M. Duffy
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
| | - Megan L. Fitzgerald
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
| | - June Chan
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
| | - Danielle C. Robinson
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
| | - Teresa A. Milner
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
- Laboratory of Neuroendocrinology, The Rockefeller University, New York, New York 10065
| | - Kenneth Mackie
- Department of Psychological and Brain Sciences and the Gill Center, Indiana University, Bloomington, Indiana 47405
| | - Virginia M. Pickel
- Department of Neurology and Neuroscience, Division of Neurobiology, Weill Cornell Medical College, New York, New York 10065
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Asensio S, Romero MJ, Romero FJ, Wong C, Alia-Klein N, Tomasi D, Wang GJ, Telang F, Volkow ND, Goldstein RZ. Striatal dopamine D2 receptor availability predicts the thalamic and medial prefrontal responses to reward in cocaine abusers three years later. Synapse 2010; 64:397-402. [PMID: 20034014 DOI: 10.1002/syn.20741] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Low levels of dopamine (DA) D2 receptor availability at a resting baseline have been previously reported in drug addicted individuals and have been associated with reduced ventral and dorsal prefrontal metabolism. The reduction in DA D2 receptor availability along with the reduced ventral frontal metabolism is thought to underlie compromised sensitivity to nondrug reward, a core characteristic of drug addiction. We therefore hypothesized that variability in DA D2 receptor availability at baseline will covary with dynamic responses to monetary reward in addicted individuals. Striatal DA D2 receptor availability was measured with [(11)C]raclopride and positron emission tomography and response to monetary reward was measured (an average of three years later) with functional magnetic resonance imaging in seven cocaine-addicted individuals. Results show that low DA D2 receptor availability in the dorsal striatum was associated with decreased thalamic response to monetary reward; while low availability in ventral striatum was associated with increased medial prefrontal (Brodmann Area 6/8/32) response to monetary reward. These preliminary results, that need to be replicated in larger sample sizes and validated with healthy controls, suggest that resting striatal DA D2 receptor availability predicts variability in functional responses to a nondrug reinforcer (money) in prefrontal cortex, implicated in behavioral monitoring, and in thalamus, implicated in conditioned responses and expectation, in cocaine-addicted individuals.
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Affiliation(s)
- Samuel Asensio
- Instituto de Drogas y Conductas Adictivas, Universidad CEU Cardenal Herrera, Avda. Seminario s/n 46113 Moncada, Valencia, Spain
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Gerretsen P, Müller DJ, Tiwari A, Mamo D, Pollock BG. The intersection of pharmacology, imaging, and genetics in the development of personalized medicine. DIALOGUES IN CLINICAL NEUROSCIENCE 2010. [PMID: 20135894 PMCID: PMC3181934 DOI: 10.31887/dcns.2009.11.4/pgerretsen] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We currently rely on large randomized trials and meta-analyses to make clinical decisions; this places us at a risk of discarding subgroup or individually specific treatment options owing to their failure to prove efficacious across entire populations. There is a new era emerging in personalized medicine that will focus on individual differences that are not evident phenomenologically. Much research is directed towards identifying genes, endophenotypes, and biomarkers of disease that will facilitate diagnosis and predict treatment outcome. We are at the threshold of being able to predict treatment response, primarily through genetics and neuroimaging. In this review we discuss the most promising markers of treatment response and adverse effects emerging from the areas of pharmacogenetics and neuroimaging in depression and schizophrenia.
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Affiliation(s)
- Philip Gerretsen
- Centre for Addiction and Mental Health, University of Toronto, Canada
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Abstract
Antipsychotic medications are widely used to manage psychotic and behavioral disorders in older adults, including primary psychotic disorders such as schizophrenia, and psychosis and behavioral disturbances associated with dementia. These two broad diagnostic indications are associated with contrasting recommended treatment durations, with the former requiring indefinite treatment across the life span. Antipsychotic drug dosing for schizophrenia is based primarily on studies of younger patients and thus may not apply to older adults. It is critically important to address the effects of aging on antipsychotic dosing given the recent emergence of data that suggest a critical role for age-related sensitivity to these drugs. Antipsychotic drugs are not only associated with somatic and neurological adverse effects but also increased all-cause mortality and sudden cardiac death in this vulnerable population. This review focuses on the sensitivity of older adults to adverse effects from antipsychotic medications and the current pharmacokinetic and pharmacodynamic explanatory models of susceptibility. Implications of recent research findings for individualized pharmacotherapy are discussed.
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D2 receptor blockade by risperidone correlates with attention deficits in late-life schizophrenia. J Clin Psychopharmacol 2009; 29:571-5. [PMID: 19910723 DOI: 10.1097/jcp.0b013e3181bf4ea3] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The negative impact of antipsychotic drugs on attention is expected to be greater in late-life schizophrenia because of the age-related changes in the dopamine receptor reserve. The objective of this study was to examine the relationship between dopamine D2 receptor blockade by risperidone and the cognitive function in late-life schizophrenia. Subjects with schizophrenia or schizoaffective disorder aged 50 or older who were receiving risperidone completed a [C]raclopride positron emission tomography scan to measure D2-binding potential in the striatum. The D2 receptor blockade by risperidone was calculated using age-corrected measures from healthy individuals and region of interest analysis of dynamic positron emission tomography data coregistered to the subjects' magnetic resonance imaging scans. Cognitive function was assessed using a battery of neuropsychological tests that included the Dementia Rating Scale-2 (DRS). Eleven subjects (mean +/- SD age, 64 +/- 8 years) participated in this study. The mean +/- SD D2 receptor blockade was 69% +/- 14% (range, 34%-80%). The age-corrected score on the attention subscale in the DRS was negatively correlated with the D2 receptor blockade. The DRS attention subscale score was lower in the subjects who experienced 74.9% or higher D2 blockade (median value, corresponding to a daily risperidone dose of >3.0 mg) than in those who did not. Although a causal attribution cannot be made in light of the cross-sectional nature of this study, the results suggest the critical importance of identifying the lowest effective dose of antipsychotic drugs in older patients with schizophrenia.
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