Dose Reduction of Risperidone and Olanzapine and Estimated Dopamine D<sub>2</sub> Receptor Occupancy in Stable Patients With Schizophrenia
Bibliographic record
Abstract
BACKGROUND: While acute-phase antipsychotic response has been attributed to 65%-80% dopamine D₂ receptor blockade, the degree of occupancy for relapse prevention in the maintenance treatment of schizophrenia remains unknown. METHOD: In this secondary study of an open-label, 28-week, randomized, controlled trial conducted between April 2009 and August 2011, clinically stable patients with schizophrenia (DSM-IV) treated with risperidone or olanzapine were randomly assigned to the reduction group (dose reduced by 50%) or maintenance group (dose kept constant). Plasma antipsychotic concentrations at peak and trough before and after dose reduction were estimated with population pharmacokinetic techniques, using 2 collected plasma samples. Corresponding dopamine D₂ occupancy levels were then estimated using the model we developed. Relapse was defined as worsening in 4 Positive and Negative Syndrome Scale-Positive subscale items: delusion, conceptual disorganization, hallucinatory behavior, and suspiciousness. RESULTS: Plasma antipsychotic concentrations were available for 16 and 15 patients in the reduction and maintenance groups, respectively. Estimated dopamine D₂ occupancy (mean ± SD) decreased following dose reduction from 75.6% ± 4.9% to 66.8% ± 6.4% at peak and 72.3% ± 5.7% to 62.0% ± 6.8% at trough. In the reduction group, 10 patients (62.5%) did not demonstrate continuous D₂ receptor blockade above 65% (ie, < 65% at trough) after dose reduction; furthermore, 7 patients (43.8%) did not achieve a threshold of 65% occupancy even at peak. Nonetheless, only 1 patient met our relapse criteria after dose reduction during the 6 months of the study. CONCLUSIONS: The results suggest that the therapeutic threshold regarding dopamine D₂ occupancy may be lower for those who are stable in antipsychotic maintenance versus acute-phase treatment. Positron emission tomography studies are warranted to further test our preliminary findings. TRIAL REGISTRATION: UMIN Clinical Trials Registry identifier: UMIN000001834.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".