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

Age, Sex, and Comedication Effects on the Steady-State Plasma Concentrations of Amisulpride in Chinese Patients with Schizophrenia

BACKGROUND

Amisulpride, a second-generation atypical antipsychotic drug, was first marketed in Europe in the 1990s. This study aimed to provide a reference for the clinical application of amisulpride. The effects of age, sex, or specific comedications on amisulpride concentrations in Chinese patients with schizophrenia in the real world were investigated.

METHODS

A retrospective study was conducted of data on amisulpride based on the therapeutic drug monitoring service database at the Zigong Affiliated Hospital of Southwest Medical University.

RESULTS

Based on the inclusion criteria, 195 plasma samples from 173 patients (67.05% female and 32.95% male patients) were included for in-depth analysis. The median daily dose of amisulpride was 400 mg/d, median plasma concentration was 457.50 ng/mL, and median concentration/dose (C/D) ratio was 1.04 ng/mL/mg/d. The daily dose of amisulpride positively correlated with measured steady-state plasma concentrations. A significant difference was observed in the subgroup analysis of the combination with valproic acid, zopiclone, or aripiprazole on plasma concentrations. Combining amisulpride with these drugs increased the C/D ratios by 0.56-, 2.31-, and 0.77-fold, respectively. After adjusting for age, the median C/D ratio was found to be significantly different between female and male patients. However, no significant differences in daily dose, plasma concentration, and C/D ratio were noted with respect to sex and age of the patients.

CONCLUSIONS

Sex differences were inferred for the first time in this study, with differential effects on daily dose, steady-state plasma concentration, and C/D ratio associated with the population. In the included study samples, blood concentrations were distributed in the range of 223.25-823.55 ng/mL, which perhaps needs to be evaluated in line with the reference range of ammonia-sulfur ratios in the Chinese population.

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.

Current Status of Therapeutic Drug Monitoring in Mental Health Treatment: A Review

Therapeutic drug monitoring (TDM) receives growing interest in different psychiatric clinical settings (emergency, inpatient, and outpatient services). Despite its usefulness, TDM remains underemployed in mental health. This is partly due to the need for evidence about the relationship between drug serum concentration and efficacy and tolerability, both in the general population and even more in subpopulations with atypical pharmacokinetics. This work aims at reviewing the scientific literature published after 2017, when the most recent guidelines about the use of TDM in mental health were written. We found 164 pertinent records that we included in the review. Some promising studies highlighted the possibility of correlating early drug serum concentration and clinical efficacy and safety, especially for antipsychotics, potentially enabling clinicians to make decisions on early laboratory findings and not proceeding by trial and error. About populations with pharmacokinetic peculiarities, the latest studies confirmed very common alterations in drug blood levels in pregnant women, generally with a progressive decrease over pregnancy and a very relevant dose-adjusted concentration increase in the elderly. For adolescents also, several drugs result in having different dose-related concentration values compared to adults. These findings stress the recommendation to use TDM in these populations to ensure a safe and effective treatment. Moreover, the integration of TDM with pharmacogenetic analyses may allow clinicians to adopt precise treatments, addressing therapy on an individual pharmacometabolic basis. Mini-invasive TDM procedures that may be easily performed at home or in a point-of-care are very promising and may represent a turning point toward an extensive real-world TDM application. Although the highlighted recent evidence, research efforts have to be carried on: further studies, especially prospective and fixed-dose, are needed to replicate present findings and provide clearer knowledge on relationships between dose, serum concentration, and efficacy/safety.

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.

Pharmacokinetics of immediate and sustained-release formulations of paroxetine: Population pharmacokinetic approach to guide paroxetine personalized therapy in chinese psychotic patients

Paroxetine is one of the most potent selective serotonin reuptake inhibitors (SSRIs) approved for treating depression, panic disorder, and obsessive-compulsive disorder. There is evidence linking genetic polymorphisms and nonlinear metabolism to the Paroxetine’s pharmacokinetic (PK) variability. The purpose of the present study was to develop a population PK (PPK) model of paroxetine in Chinese patients, which was used to define the paroxetine’s PK parameters and quantify the effect of clinical and baseline demographic factors on these PK characteristics. The study included 184 inpatients with psychosis (103 females and 81 males), with a total of 372 serum concentrations of paroxetine for PPK analyses. The total daily dosage ranged from 20 to 75 mg. One compartment model could fit the PKs characterize of paroxetine. Covariate analysis revealed that dose, formulation, and sex had a significant effect on the PK parameters of paroxetine; however, there was no evident genetic influence of CYP2D6 enzymes on paroxetine concentrations in Chinese patients. The study determined that the population’s apparent distribution volume (V/F) and apparent clearance (CL/F), respectively, were 8850 and 21.2 L/h. The CL/F decreased 1-2-fold for each 10 mg dose increase, whereas the different formulations caused a decrease in V/F of 66.6%. Sex was found to affect bioavailability (F), which decreased F by 47.5%. Females had higher F values than males. This PPK model described data from patients with psychosis who received paroxetine immediate-release tablets (IR-T) and/or sustained-release tablets (SR-T). Paroxetine trough concentrations and relative bioavailability were different between formulations and sex. The altered serum concentrations of paroxetine resulting from individual variants and additive effects need to be considered, to optimize the dosage regimen for individual patients.