This application from a new independent investigator seeks support for a study that addresses an important problem in geriatric psychopharmacology. Schizophrenia is a life-long illness requiring daily treatment with antipsychotic medication. In contrast to antipsychotic dosing in younger patients, the minimal therapeutic dose in older patients remains unknown. Clinical guidelines based primarily on expert consensus have recommended the use of lower antipsychotic doses in older patients with schizophrenia, and dose reduction has been advocated for patients stable on higher doses. However these guidelines are based on limited empirical data that do not take into account mechanistic processes involved in drug sensitivity associated with aging. Previous Positron Emission Tomography (PET) studies in young and mid-life patients with schizophrenia have established a therapeutic window of antipsychotic drug occupancy at striatal dopamine D2/3 receptors which has been successfully employed in predicting the clinically effective doses for new and established antipsychotic drugs in younger patients. Towards the goal of establishing the lowest effective maintenance dose of antipsychotic medication in older patients with early-onset schizophrenia, we propose a PET study using a prospective within-subject design. We will determine an estimate of risperidone D2/3 occupancy associated with maintenance of response in 40 patients 60 years and older with onset of schizophrenia before the age of 45 years and maintained on a single antipsychotic (risperidone) at a steady high dose of >3.5 mg per day for at least one year. They will undergo a gradual dose reduction up to 40% of their baseline dose to a target dose not lower than the recommended dose range of 1.25 - 3.5 mg/day. A [11C]raclopride PET scan will be completed at baseline and after dose reduction. They will then be followed for 6 months to determine clinical outcome. If they show signs of clinical deterioration, they will have their dose titrated up until clinical response is restored, and then undergo a third PET scan to establish the drug binding at the clinically effective dose. The results of this study will be used in future studies incorporating population pharmacokinetic methodology, translating the drug occupancy data collected in this to individualized dosing of risperidone for older patients with schizophrenia. This can be achieved in clinical practice using little more than standard laboratory assays to determine the lowest effective antipsychotic dose necessary for maintenance of therapeutic effect in older patients with schizophrenia, a clinical question of major public health significance.

Public Health Relevance

Schizophrenia is a life-long condition that requires long-term treatment with antipsychotic medications to prevent relapse of psychotic symptoms. As patients with schizophrenia become older, they become more sensitive to medication side effects and require a reduction of antipsychotic dose. However, since the minimal effective dose of antipsychotic medications in older patients is not known, most of them are treated with doses that are too high. Studying the extent of antipsychotic drug binding to brain receptors using positron emission tomography (PET) will allow for the prediction of the lowest effective dose required to maintain wellness in older patients.

National Institute of Health (NIH)
National Institute of Mental Health (NIMH)
Research Project (R01)
Project #
Application #
Study Section
Interventions Committee for Adult Disorders (ITVA)
Program Officer
Evans, Jovier D
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Centre for Addiction and Mental Health
Zip Code
Caravaggio, Fernando; Fervaha, Gagan; Chung, Jun Ku et al. (2016) Exploring personality traits related to dopamine D2/3 receptor availability in striatal subregions of humans. Eur Neuropsychopharmacol 26:644-52
Chung, Jun Ku; Nakajima, Shinichiro; Plitman, Eric et al. (2016) Î’-Amyloid Burden is Not Associated with Cognitive Impairment in Schizophrenia: A Systematic Review. Am J Geriatr Psychiatry 24:923-39
Chung, Jun Ku; Plitman, Eric; Nakajima, Shinichiro et al. (2016) Cortical Amyloid β Deposition and Current Depressive Symptoms in Alzheimer Disease and Mild Cognitive Impairment. J Geriatr Psychiatry Neurol 29:149-59
Fervaha, Gagan; Caravaggio, Fernando; Mamo, David C et al. (2016) Lack of association between dopaminergic antagonism and negative symptoms in schizophrenia: a positron emission tomography dopamine D2/3 receptor occupancy study. Psychopharmacology (Berl) 233:3803-3813
Nakajima, Shinichiro; Uchida, Hiroyuki; Bies, Robert R et al. (2016) Dopamine D2/3 Receptor Occupancy Following Dose Reduction Is Predictable With Minimal Plasma Antipsychotic Concentrations: An Open-Label Clinical Trial. Schizophr Bull 42:212-9
Caravaggio, Fernando; Borlido, Carol; Hahn, Margaret et al. (2015) Reduced insulin sensitivity is related to less endogenous dopamine at D2/3 receptors in the ventral striatum of healthy nonobese humans. Int J Neuropsychopharmacol 18:pyv014
Tsuboi, T; Bies, R R; Suzuki, T et al. (2015) Predicting Plasma Olanzapine Concentration Following a Change in Dosage: A Population Pharmacokinetic Study. Pharmacopsychiatry 48:286-91
Graff-Guerrero, Ariel; Rajji, Tarek K; Mulsant, Benoit H et al. (2015) Evaluation of Antipsychotic Dose Reduction in Late-Life Schizophrenia: A Prospective Dopamine D2/3 Receptor Occupancy Study. JAMA Psychiatry 72:927-34
Caravaggio, Fernando; Raitsin, Sofia; Gerretsen, Philip et al. (2015) Ventral striatum binding of a dopamine D2/3 receptor agonist but not antagonist predicts normal body mass index. Biol Psychiatry 77:196-202
Nakajima, Shinichiro; Caravaggio, Fernando; Mamo, David C et al. (2015) Dopamine D₂/₃ receptor availability in the striatum of antipsychotic-free older patients with schizophrenia-A [¹¹C]-raclopride PET study. Schizophr Res 164:263-7

Showing the most recent 10 out of 25 publications