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A Population Approach to Guide Amisulpride Dose Adjustments in Older Patients With Alzheimer’s Disease

Suzanne Reeves, PhD; Julie Bertrand, PhD; Emma McLachlan, MBChB; Fabrizia D†Antonio, MBBS; Stuart Brownings, BSc; Akshay Nair, MBBS; Suki Greaves, MBBS; Alan Smith, MBBS; Joel T. Dunn, PhD; Paul Marsden, PhD; Robert Kessler, MD; Hiroyuki Uchida, MD, PhD; David Taylor, PhD; and Robert Howard, MD

Published: August 23, 2017

Article Abstract

Objective: We have previously reported high dopamine D2/3 receptor occupancies at low amisulpride concentrations in older people with Alzheimer’s disease (AD), during off-label treatment of AD-related psychosis. This post hoc analysis explored pharmacokinetic (concentration) and pharmacodynamic (prolactin, D2/3 occupancy) contributions to symptom reduction and extrapyramidal side effects (EPS) to inform AD-specific dose adjustments.

Methods: Population pharmacokinetic-pharmacodynamic models were developed by combining pharmacokinetic data from a phase 1 study in 20 healthy older people with pharmacokinetic prolactin, [18F]fallypride D2/3 receptor imaging, and clinical outcome data from 28 older patients prescribed open amisulpride (25-75 mg/d) to treat AD-related psychosis. Model predictions were used to simulate dose-response and dose-EPS.

Results: Symptom reduction (delusions) was associated with amisulpride concentration (P = 1.3e-05) and D2/3 occupancy (P < .01, caudate, putamen, thalamus). Model predictions suggested that across concentrations of 40-100 ng/mL, and occupancies of 40% to 70% in the caudate and thalamus and 30% to 60% in the putamen, there was a 50% to 90% probability of response and < 30% probability of EPS. Simulations, based on concentration-delusions and concentration-EPS model outputs, showed that 50 mg/d of amisulpride was the appropriate dose to achieve this target range in those aged > 75 years; increasing the dose to 75 mg/d increased the risk of EPS, particularly in those aged > 85 years of low body weight.

Conclusions: These findings argue strongly for the consideration of age- and weight-based dose adjustments in older patients with AD-related psychosis and indicate that 50 mg/d of amisulpride may be both the minimal clinically effective dose and, in those aged > 75 years, the maximally tolerated dose.

Volume: 78

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