Plasma amisulpride in relation to prescribed dose, clozapine augmentation, and other factors: data from a therapeutic drug monitoring service, 2002-2010

Population pharmacokinetics of Amisulpride in Chinese patients with schizophrenia with external validation: the impact of renal function

Introduction: Amisulpride is primarily eliminated via the kidneys. Given the clear influence of renal clearance on plasma concentration, we aimed to explicitly examine the impact of renal function on amisulpride pharmacokinetics (PK) via population PK modelling and Monte Carlo simulations. Method: Plasma concentrations from 921 patients (776 in development and 145 in validation) were utilized. Results: Amisulpride PK could be described by a one-compartment model with linear elimination where estimated glomerular filtration rate, eGFR, had a significant influence on clearance. All PK parameters (estimate, RSE%) were precisely estimated: apparent volume of distribution (645 L, 18%), apparent clearance (60.5 L/h, 2%), absorption rate constant (0.106 h-1, 12%) and coefficient of renal function on clearance (0.817, 10%). No other significant covariate was found. The predictive performance of the model was externally validated. Covariate analysis showed an inverse relationship between eGFR and exposure, where subjects with eGFR= 30 mL/min/1.73 m2 had more than 2-fold increase in AUC, trough and peak concentration. Simulation results further illustrated that, given a dose of 800 mg, plasma concentrations of all patients with renal impairment would exceed 640 ng/mL. Discussion: Our work demonstrated the importance of renal function in amisulpride dose adjustment and provided a quantitative framework to guide individualized dosing for Chinese patients with schizophrenia.

A 5-year retrospective study of amisulpride steady-state plasma concentration in patients with schizophrenia in real-life settings based on therapeutic drug monitoring data

OBJECTIVE

Here, we present a retrospective analysis of the last 5 years' data collected in real-life settings as direct evidence to evaluate the optimal therapeutic window of amisulpride (AMI) for psychiatric patients.

METHODS

Retrospective analysis of the therapeutic drug monitoring (TDM) results of AMI in outpatients and inpatients were obtained from the Xi'an Mental Health Center from 2017 to 2021.

RESULTS

The interquartile (P25-P75) AMI concentrations ranged 212.20-574.25 ng/mL. The results showed that the proportion of outpatients who received TDM once was significantly higher than that of inpatients who received TDM once (P < 0.001), whereas the reverse was true for those who experienced TDM more than twice (P < 0.001). Higher estimated plasma concentrations were identified in inpatients, female patients, and patients over 59 years of age. Nearly 57.21% of the samples had high concentrations (>320 ng/mL).

CONCLUSIONS

The optimal therapeutic reference range for AMI may require reconstruction to guide the use of AMI for the treatment of schizophrenia.

Amisulpride steady-state plasma concentration and adverse reactions in patients with schizophrenia: a study based on therapeutic drug monitoring data

The aim of the study was to evaluate the reference range of amisulpride for Chinese patients with schizophrenia and to assess its possible influencing factors based on therapeutic drug monitoring information. The relative adverse reactions of patients induced by amisulpride were also systematically investigated. A total of 425 patients with schizophrenia were assessed, including Positive and Negative Syndrome Scales, Treatment Emergent Symptom Scale, blood routine examination, hepatorenal function, lipids, hormones, as well as myocardial enzymes at baseline, and following treatment with amisulpride for 8 weeks. The steady-state plasma concentration of amisulpride was assayed using two-dimensional liquid chromatography. At the same dose, the amisulpride plasma concentration of patients combined with clozapine was higher than that without clozapine. The therapeutic reference range of amisulpride can be defined as 230.3-527.1 ng/ml for Chinese patients with schizophrenia. The potential side effects appear to be associated with significantly increased levels of LDH, CK, creatine kinase isoenzyme (CK-MB), TC and decreased level of E 2 , relative to the amisulpride plasma concentration. These findings could provide individualized medication and reduce the adverse effects of amisulpride for Chinese patients with schizophrenia.

Increased amisulpride serum concentration in a patient treated with concomitant pregabalin and trazodone: a case report

We report on the case of a 46-year-old woman with generalized anxiety disorder, paranoid personality disorder, and mild reduction in glomerular filtration rate (GFR). She was treated with pregabalin, trazodone, hydroxyzine, and clonazepam before hospital admission. Pharmacotherapy for the patient was changed during her first week in the hospital. Dosing of hydroxyzine and clonazepam was gradually decreased, and then these two drugs were withdrawn. Treatment with amisulpride was started on the fourth day after admission, and amisulpride serum levels were then measured three times as a part of therapeutic drug monitoring (TDM). The serum concentration of amisulpride detected during concurrent use of trazodone and pregabalin was approximately twice the therapeutic range for amisulpride. When the dose of pregabalin was reduced by half, the serum concentration of amisulpride decreased to therapeutic serum levels. We hypothesize that an interaction between amisulpride and pregabalin was responsible for the increased amisulpride concentration since both drugs are almost exclusively excreted from the body by the renal route. Pregabalin-amisulpride interaction might also be influenced by concomitant therapy with trazodone or a mild reduction in GFR. However, we only have clinical evidence for an interaction between amisulpride and pregabalin because after we halved the dose of pregabalin, the amisulpride concentration decreased, and the C/D ratio normalized. This could be helpful information for psychiatrists in order to avoid drug-drug interactions between amisulpride and pregabalin. We recommend TDM of amisulpride in patients treated concomitantly with other drugs eliminated mainly by the kidneys.

Modeling and Simulation for Individualized Therapy of Amisulpride in Chinese Patients with Schizophrenia: Focus on Interindividual Variability, Therapeutic Reference Range and the Laboratory Alert Level

Purpose

To explain the high inter-individual variability (IIV) and the frequency of exceeding the therapeutic reference range and the laboratory alert level of amisulpride, a population pharmacokinetic (PPK) model in Chinese patients with schizophrenia was built based on therapeutic drug monitoring (TDM) data to guide individualized therapy.

Patients and Methods

Plasma concentration data (330 measurements from 121 patients) were analyzed using a nonlinear mixed-effects modeling (NONMEM) approach with first-order conditional estimation with interaction (FOCE I). The concentrations of amisulpride were detected by HPLC-MS/MS. Age, weight, sex, combination medication history and renal function status were evaluated as main covariates. The model was internally validated using goodness-of-fit, bootstrap and normalized prediction distribution error (NPDE). Recommended dosage regimens for patients with key covariates were estimated on the basis of Monte Carlo simulations and the established model.

Results

A one-compartment model with first-order absorption and elimination was found to adequately characterize amisulpride concentration in Chinese patients with schizophrenia. The population estimates of the apparent volume of distribution (V/F) and apparent clearance (CL/F) were 12.7 L and 1.12 L/h, respectively. Age significantly affected the clearance of amisulpride and the final model was as follows: CL/F=1.04×(AGE/32)^−0.624 (L/h). To avoid exceeding the laboratory alert level (640 ng/mL), the model-based simulation results showed that the recommended dose of amisulpride was no more than 600 mg/d for patients aged 60 years, 800 mg/d for those aged 40 years and 1200 mg/d for those aged 20 years, respectively.

Conclusion

Dosage optimization of amisulpride can be carried out according to age to reduce the risk of adverse reactions. The model can be used as a suitable tool for designing individualized therapy for Chinese patients with schizophrenia.

A systematic review and combined meta-analysis of concentration of oral amisulpride

AIMS

Amisulpride, a first-line schizophrenia treatment, has shown large interindividual variability in plasma/serum levels, often outside the reference range (100-320 ng/mL). This study aims to clarify the impact of dose, sex, age and related factors for the interpatient variability in amisulpride plasma/serum concentration.

METHODS

Both English and Chinese databases were searched from their inception to May 16, 2019, using the terms: amisulpride and (plasma OR serum OR blood OR "drug monitoring" OR concentration). Studies reporting concentrations and either a dose, associated factor, clinical outcome or side effect were included.

RESULTS

Fourteen studies with 1628 participants were eventually included. Eligible articles yielded data on drug concentration and dose, averaging 333.9 (95% confidence interval [CI]: 294.5-373.3) ng/mL and 636.2 (95% CI: 549.7-722.6) mg/d, respectively. The calculated mean concentration-to-dose (C/D) ratio was 0.60 (95% CI: 0.52-0.67) (ng/mL)/mg. Subgroup analysis suggested that female patients on combined lithium-amisulpride have higher concentration levels and C/D ratios. Age was slight positive associated with C/D ratio while not for plasma level. Smoker patients have high concentration level than nonsmoking patients but not for C/D. Responsive and nonresponsive groups did not differ in concentration and C/D.

CONCLUSION

Pooled concentration levels of amisulpride were higher than recommended with wide individual variation, especially in older patients, female patients and patients taking amisulpride combined with lithium. The specific therapeutic reference range for amisulpride may require reconstruction, which should consider the influence of age, sex, kidney function, drug-drug interactions, different dose regimens and sampling times in future study.

A Compilation of Serum Concentrations of 12 Antipsychotic Drugs in a Therapeutic Drug Monitoring Setting

BACKGROUND

No comprehensive collection of routine therapeutic drug monitoring data for antipsychotic drugs has been published.

METHODS

In this compilation, data on 12 antipsychotics are presented. The drugs included are amisulpride (n = 506), aripiprazole (n = 1610), clozapine (n = 1189), flupentixol (n = 215), haloperidol (n = 390), olanzapine (n = 10,268), perphenazine (n = 1065), quetiapine (n = 5853), risperidone (n = 3255), sertindole (n = 111), ziprasidone (n = 1235), and zuclopenthixol (n = 691). Because only one sample per patient is included, the number of patients equals the number of samples. For each drug, median serum concentrations as well as that of the 10th and 90th percentiles are given for a range of daily doses. Comparisons are made between males and females, between patients younger than 65 years and 65 years and older, and between those treated with a low and a high dose of each drug. The concentration-to-dose (C/D) ratio is the primary variable used in these comparisons. Coefficients of variation (CVs) for the serum concentrations of each drug within and between subjects are presented.

RESULTS

In general, the C/D ratios were higher in females than in males, higher in those 65 years and older than in younger subjects, and lower in those treated with higher doses than in those treated with lower doses. CVs between individuals were larger than within subjects, and the CVs were highest for the drugs with short elimination half-lives.

CONCLUSIONS

For each antipsychotic drug, the results presented can serve as a reference tool for pharmacokinetic interpretation of the individual patient's serum drug level. The compiled serum concentrations and the C/D ratios can support the physician's decision when individualizing dosing and determining treatment strategies for a specific patient.

Thorough QT study of the effect of intravenous amisulpride on QTc interval in Caucasian and Japanese healthy subjects

AIM

The D₂ /D₃ antagonist amisulpride has shown promising efficacy against postoperative nausea and vomiting (PONV) at low doses. We investigated whether intravenous amisulpride has an effect on the QTc interval in a formal Thorough QT study (TQT).

METHODS

This was a randomized, double-blind, placebo and positive-controlled, four-way crossover study. Forty healthy Caucasian and Japanese subjects were included to receive a single administration of 5 mg and 40 mg of i.v. amisulpride or a single oral dose of moxifloxacin or placebo per period.

RESULTS

The therapeutic dose of 5 mg amisulpride was associated with a slight, transient increase in mean ΔΔQTcF, from 2.0 ms prior to dosing to a peak of 5 ms (90% CI: 2.8, 7.1 ms) at 8 min, decreasing to 2.1 ms at 30 min after dosing. The supra-therapeutic dose of 40 mg given at twice the infusion rate was associated with prolongation in ΔΔQTcF peaking at 23.4 ms (90% CI: 21.3, 25.5 ms) at the end of infusion (8 min), returning below 10 ms within 1.5 h. Assay sensitivity was confirmed; ΔΔQTcF had increased by 12.3 ms (90% CI 10.1, 14.6 ms) at 4 h post-dose. The PK-PD relationship revealed no differences between Caucasian and Japanese subjects (p-value > 0.5).

CONCLUSIONS

Amisulpride has a plasma concentration-dependent effect on the QTc interval. The proposed therapeutic dose for management of PONV does not lead to a prolongation of QTcF above the threshold of regulatory concern, while such effect could not be excluded for the supratherapeutic dose.

A population approach to characterise amisulpride pharmacokinetics in older people and Alzheimer's disease

INTRODUCTION

Current prescribing guidelines for the antipsychotic amisulpride are based largely on pharmacokinetic (PK) studies in young adults, and there is a relative absence of data on older patients, who are at greatest risk of developing adverse events.

METHODS

This study aimed to develop a population PK model for amisulpride specifically in older people, by combining data from a richly sampled phase 1, single (50 mg) dose study in healthy older people (n = 20, 65-79 years), with a clinical dataset obtained during off label, low-dose (25-75 mg daily) amisulpride prescribing in older people with Alzheimer's disease (AD) (n = 25, 69-92 years), as part of an observational study.

RESULTS

After introducing a scaling factor based on body weight, age accounted for 20 % of the inter-individual variability in drug clearance (CL), resulting in a 54 % difference in CL between those aged 65 and those aged 85 years, and higher blood concentrations in older patients.

DISCUSSION

These findings argue for the consideration of age and weight-based dose stratification to optimise amisulpride prescribing in older people, particularly in those aged 85 years and above.

Antipsychotic therapeutic drug monitoring: psychiatrists' attitudes and factors predicting likely future use

BACKGROUND

This study aimed to explore predictive factors for future use of therapeutic drug monitoring (TDM) and to further examine psychiatrists' current prescribing practices and perspectives regarding antipsychotic TDM using plasma concentrations.

METHOD

A cross-sectional study for consultant psychiatrists using a postal questionnaire was conducted in north-west England. Data were combined with those of a previous London-based study and principal axis factor analysis was conducted to identify predictors of future use of TDM.

RESULTS

Most of the 181 participants (82.9%, 95% confidence interval 76.7-87.7%) agreed that 'if TDM for antipsychotics were readily available, I would use it'. Factor analysis identified five factors from the original 35 items regarding TDM. Four of the factors significantly predicted likely future use of antipsychotic TDM and together explained 40% of the variance in a multivariate linear regression model. Likely future use increased with positive attitudes and expectations, and decreased with potential barriers, negative attitudes and negative expectations. Scientific perspectives of TDM and psychiatrist characteristics were not significant predictors.

CONCLUSION

Most senior psychiatrists indicated that they would use antipsychotic TDM if available. However, psychiatrists' attitudes and expectations and the potential barriers need to be addressed, in addition to the scientific evidence, before widespread use of antipsychotic TDM is likely in clinical practice.

Population pharmacokinetic/pharmacodynamic model of clozapine for characterizing the relationship between accumulated exposure and PANSS scores in patients with schizophrenia

BACKGROUND

The aim of this study was to characterize the relationship between accumulated exposure of clozapine and changes in Positive and Negative Syndrome Scale (PANSS) score in Chinese patients with schizophrenia by pharmacokinetic/pharmacodynamic (PK/PD) modeling.

METHODS

Sparse clozapine PK data and PANSS scores were collected from 2 clinical studies of Chinese inpatients with schizophrenia. Two other rich PK data sets were included for more accurate assessment of clozapine PK characteristics. The relationship between clozapine-accumulated exposure and PANSS score was investigated using linear, log-linear, E(max), and sigmoid models, and each model was evaluated using visual predictive condition and normalized prediction distribution error methods. Simulations based on the final PK/PD model were preformed to investigate the effect of clozapine on PANSS scores under different dose regimens.

RESULTS

A total of 1391 blood clozapine concentrations from 198 subjects (180 patients and 18 healthy volunteers) and 576 PANSS scores from 137 patients were included for PK and PK/PD analysis. A first-order 2-compartment PK model with covariates gender and smoking status influencing systemic clearance adequately described the PK profile of clozapine. The decrease in total PANSS score during treatment was best characterized using cumulated clozapine area under the curve (AUC) data in the E(max) model. The maximum decrease in PANSS during clozapine treatment (Emax) was 55.4%, and the cumulated AUC(50) (cAUC(50)) required to attain half of E(max) was 296 mg·L(-1)·h(-1)·d(-1). The simulations demonstrated that the accelerated dose titration and constant dose regimens achieved a similar maximum drug response but with a slower relief of symptoms in dose titration regimen.

CONCLUSIONS

The PK/PD model can describe the clinical response as measured by decreasing PANSS score during treatment and may be useful for optimizing the dose regimen for individual patients.

Augmentation of clozapine with amisulpride: an effective therapeutic strategy for violent treatment-resistant schizophrenia patients in a UK high-security hospital

OBJECTIVE

Clozapine is used in the management of treatment-resistant schizophrenia and is effective in reducing aggression; however a subgroup of patients is poorly responsive. For violent patients in this group, there is limited literature on the use of strategies to augment clozapine with other agents. Here we present a case series of 6 schizophrenia patients, within a high-security hospital, who have a history of serious violence and who were treated with clozapine augmented with amisulpride.

METHODS

We reviewed case notes and health records for evidence of violence/aggression and positive factors such as engagement in activities, and Clinical Global Impression (CGI) scores were formulated. We also examined metabolic parameters before and after augmentation.

RESULTS

All 6 of the patients showed clinical improvement in symptoms and a reduction in their risk of violence to others. Five patients had a reduction in number of violent/aggressive incidents, and all patients showed improvement in engagement in occupational, vocational, and/or psychological work. Metabolic parameters were largely unchanged except for 1 patient whose Body Mass Index (BMI) increased. Five patients reported side effects as unchanged or improved.

CONCLUSION

These schizophrenia patients with a history of violence showed clinical improvement and reduced aggression and violence with amisulpride augmentation of clozapine. To our knowledge, this is the first report of an antiaggressive benefit of this combination in forensic psychiatric patients. Further studies are warranted to establish the efficacy and anti-aggressive effects of amisulpride augmentation of clozapine.