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

Bioequivalence of 200 mg Amisulpride Tablets in Healthy Chinese Volunteers under Fasting and Fed Conditions

In this study, we compared the pharmacokinetics and safety of a new generic product and a branded reference product of amisulpride tablets. Additionally, we assessed the bioequivalence of the 2 products in healthy Chinese volunteers to acquire sufficient evidence for the marketing approval of the generic drug. Thirty volunteers under fasting and fed conditions were randomly administered a single dose of the test or reference drug orally, followed by a 7-day washout period. The pharmacokinetic parameters were obtained by the concentration-time profiles, including the area under the plasma concentration-time curve (AUC) over the dosing interval, AUC from time zero to infinity, maximum plasma concentration, time to achieve maximum plasma concentration, and elimination half-life. AUC from time zero to infinity of amisulpride in the postprandial group was reduced by approximately 25%, suggesting that a high-fat diet can affect this parameter. In the aspect of safety, no serious adverse events occurred. This study demonstrated that generic and reference products of amisulpride tablets were bioequivalent in healthy Chinese volunteers under fasting and fed conditions.

Interaction of amisulpride with GLUT1 at the blood-brain barrier. Relevance to Alzheimer's disease

Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.

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.

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.

Risk of Prolonged Corrected QT Interval With Amisulpride Therapy for Renal Function Management in Patients With Schizophrenia

BACKGROUND

Amisulpride (AMI) is a popular antipsychotic drug prescribed for the management of schizophrenia. However, patients may experience prolonged corrected QT (QTc) interval. We therefore aimed to assess the risk factors for QTc prolongation during AMI therapy in patients with schizophrenia.

METHODS

This study retrospectively enrolled 271 patients with schizophrenia. Continuous variables were analyzed with a t test or analysis of variance, and categorical variables were analyzed with a χ test. Patients with and without QTc prolongation were compared using a backward stepwise logistic regression analysis to identify the important variables.

RESULTS

Comedication of AMI with clozapine (odds ratio, 3.5 [95% confidence interval, 1.3-9.7]) and decreased renal function (mildly decrease, 3.4 [1.2-10.1]; mild to moderately decreased, 4.8 [1.3-17.3]; moderately decreased, 13.6 [2.0-90.6]) were identified as the independent risk factors of QTc prolongation. The dose-normalized plasma concentration of AMI (plasma concentration per dose) was significantly higher in the QTc prolongation group (z = -1.735, P = 0.015) and renal dysfunction group (F = 16.002, P < 0.001).

CONCLUSIONS

Renal function should be monitored in patients prescribed with AMI, particularly in those taking clozapine. Plasma concentration per dose values can be considered as a risk factor of QTc interval prolongation. The founding help clinicians to analyze the risk of QTc prolongation before prescribing AMI and to monitor QTc prolongation during AMI therapy.

A novel and sensitive method for determination of amisulpride in human plasma by two-dimensional liquid chromatography

A novel and sensitive heart-cutting two-dimensional liquid chromatography with ultraviolet detection method (2D-LC-UV) was developed and validated for determination of amisulpride in human plasma. The 2D-LC system consists of a first dimensional (¹ D) LC column and a middle transfer column as well as a second-dimensional (² D) LC column. After simple protein precipitation, the sample was directly injected into the introduction valve of the 2D-LC system. The ¹ D column, playing a role of primary separation and preconcentration for complex plasma matrices, transferred the targets to the intermediate column. Following capture of targets on the middle column online, the analytes were transferred to the ² D separation column by a six-port valve. The ² D column, avoiding interference from the plasma matrix, completed further separation and quantification. An assistant pump was optimized for primary enrichment as well as final elution in the heart-cutting mode. The analytical time of amisulpride was 7.401 min. The accuracy was between 0.48 and 8.49%, while the intra- and inter-day precisions ranged from 0.9 to 3.1% and from 1.7% to 3.3%, respectively. The linear range of amisulpride was 48.15-2,407.59 ng/ml, while the extraction recovery was 98.7-101.3%. The strategy established in the study, which was successfully applied to therapeutic drug monitoring of amisulpride for routine clinical detection, displays high sensitivity, good repeatability, convenience and low cost.

Region-specific blood-brain barrier transporter changes leads to increased sensitivity to amisulpride in Alzheimer's disease

BACKGROUND

Research into amisulpride use in Alzheimer's disease (AD) implicates blood-brain barrier (BBB) dysfunction in antipsychotic sensitivity. Research into BBB transporters has been mainly directed towards the ABC superfamily, however, solute carrier (SLC) function in AD has not been widely studied. This study tests the hypothesis that transporters for organic cations contribute to the BBB delivery of the antipsychotics (amisulpride and haloperidol) and is disrupted in AD.

METHODS

The accumulation of [3H]amisulpride (3.7-7.7 nM) and [3H]haloperidol (10 nM) in human (hCMEC/D3) and mouse (bEnd.3) brain endothelial cell lines was explored. Computational approaches examined molecular level interactions of both drugs with the SLC transporters [organic cation transporter 1 (OCT1), plasma membrane monoamine transporter (PMAT) and multi-drug and toxic compound extrusion proteins (MATE1)] and amisulpride with the ABC transporter (P-glycoprotein). The distribution of [3H]amisulpride in wildtype and 3×transgenic AD mice was examined using in situ brain perfusion experiments. Western blots determined transporter expression in mouse and human brain capillaries .

RESULTS

In vitro BBB and in silico transporter studies indicated that [3H]amisulpride and [3H]haloperidol were transported by the influx transporter, OCT1, and efflux transporters MATE1 and PMAT. Amisulpride did not have a strong interaction with OCTN1, OCTN2, P-gp, BCRP or MRP and could not be described as a substrate for these transporters. Amisulpride brain uptake was increased in AD mice compared to wildtype mice, but vascular space was unaffected. There were no measurable changes in the expression of MATE1, MATE2, PMAT OCT1, OCT2, OCT3, OCTN1, OCTN2 and P-gp in capillaries isolated from whole brain homogenates from the AD mice compared to wildtype mice. Although, PMAT and MATE1 expression was reduced in capillaries obtained from specific human brain regions (i.e. putamen and caudate) from AD cases (Braak stage V-VI) compared to age matched controls (Braak stage 0-II).

CONCLUSIONS

Together our research indicates that the increased sensitivity of individuals with Alzheimer's to amisulpride is related to previously unreported changes in function and expression of SLC transporters at the BBB (in particular PMAT and MATE1). Dose adjustments may be required for drugs that are substrates of these transporters when prescribing for individuals with AD.

Amisulpride: Real-World Evidence of Dose Adaptation and Effect on Prolactin Concentrations and Body Weight Gain by Pharmacokinetic/Pharmacodynamic Analyses

BACKGROUND

Amisulpride is an antipsychotic used in a wide range of doses. One of the major adverse events of amisulpride is hyperprolactinemia, and the drug might also induce body weight gain.

OBJECTIVE

The aims of this work were to characterize the pharmacokinetics of amisulpride in order to suggest optimal dosage regimens to achieve the reference range of trough concentrations at steady-state (C_min,ss) and to describe the relationship between drug pharmacokinetics and prolactin and body weight data.

METHODS

The influence of clinical and genetic characteristics on amisulpride pharmacokinetics was quantified using a population approach. The final model was used to simulate C_min,ss under several dosage regimens, and was combined with a direct E_max model to describe the prolactin data. The effect of model-based average amisulpride concentrations over 24 h (C_av) on weight was estimated using a linear model.

RESULTS

A one-compartment model with first-order absorption and elimination best fitted the 513 concentrations provided by 242 patients. Amisulpride clearance significantly decreased with age and increased with lean body weight (LBW). C_min,ss was higher than the reference range in 65% of the patients aged 60 years receiving 400 mg twice daily, and in 82% of the patients aged > 75 years with a LBW of 30 kg receiving 200 mg twice daily. The pharmacokinetic/pharmacodynamic model included 101 prolactin measurements from 68 patients. The E_max parameter was 53% lower in males compared with females. Model-predicted prolactin levels were above the normal values for C_min,ss within the reference range. Weight gain did not depend on C_av.

CONCLUSIONS

Amisulpride treatment might be optimized when considering age and body weight. Hyperprolactinemia and weight gain do not depend on amisulpride concentrations. Modification of the amisulpride dosage regimen is not appropriate to reduce prolactin concentrations and alternative treatment should be considered.

Therapeutic D2/3 receptor occupancies and response with low amisulpride blood concentrations in very late-onset schizophrenia-like psychosis (VLOSLP)

OBJECTIVE

Antipsychotic drug sensitivity in very late-onset schizophrenia-like psychosis (VLOSLP) is well documented, but poorly understood. This study aimed to investigate blood drug concentration, D2/3 receptor occupancy and outcome in VLOSLP during open amisulpride prescribing, and compare this with Alzheimer's disease (AD).

METHODS

Blood drug concentration, prolactin, symptoms and extrapyramidal side-effects (EPS) were serially assessed during dose titration. [¹⁸ F]fallypride imaging was used to quantify D2/3 receptor occupancy. Average steady-state amisulpride concentration (Caverage, ng/ml) was estimated by incorporating pharmacokinetic (PK) data into an existing population PK model (25 AD participants, 20 healthy older people).

RESULTS

Eight patients (target 20) were recruited (six women; 76 + - 6 years; six treatment compliant; five serially sampled; three with paired imaging data). Mean + - SD symptom reduction was 74 ± 12% (50-100 mg/day; 92.5 + -39.4 ng/ml). Mild EPS emerged at 96 ng/ml (in AD, severe EPS, 50 mg/day, 60 ng/ml). In three participants, imaged during optimal treatment (50 mg/day; 41-70 ng/ml), caudate occupancy was 44-59% (58-74% in AD across a comparable Caverage).

CONCLUSIONS

Despite the small sample size, our findings are highly relevant as they suggest that, as in AD, 50 mg/day amisulpride is associated with >40% occupancy and clinically relevant responses in VLOSLP. It was not possible to fully characterise concentration-occupancy relationships in VLOSLP, and it is thus unclear whether the greater susceptibility of those with AD to emergent EPS was accounted for by increased central drug access. Further investigation of age- and diagnosis-specific threshold sensitivities is warranted, to guide amisulpride prescribing in older people, and therapeutic drug monitoring studies offer a potentially informative future approach. Copyright © 2017 John Wiley & Sons, Ltd.

Therapeutic window of dopamine D2/3 receptor occupancy to treat psychosis in Alzheimer's disease

See Caravaggio and Graff-Guerrero (doi:10.1093/awx023) for a scientific commentary on this article.Antipsychotic drugs, originally developed to treat schizophrenia, are used to treat psychosis, agitation and aggression in Alzheimer's disease. In the absence of dopamine D2/3 receptor occupancy data to inform antipsychotic prescribing for psychosis in Alzheimer's disease, the mechanisms underpinning antipsychotic efficacy and side effects are poorly understood. This study used a population approach to investigate the relationship between amisulpride blood concentration and central D2/3 occupancy in older people with Alzheimer's disease by combining: (i) pharmacokinetic data (280 venous samples) from a phase I single (50 mg) dose study in healthy older people (n = 20, 65-79 years); (ii) pharmacokinetic, 18F-fallypride D2/3 receptor imaging and clinical outcome data on patients with Alzheimer's disease who were prescribed amisulpride (25-75 mg daily) to treat psychosis as part of an open study (n = 28; 69-92 years; 41 blood samples, five pretreatment scans, 19 post-treatment scans); and (iii) 18F-fallypride imaging of an antipsychotic free Alzheimer's disease control group (n = 10, 78-92 years), to provide additional pretreatment data. Non-linear mixed effects modelling was used to describe pharmacokinetic-occupancy curves in caudate, putamen and thalamus. Model outputs were used to estimate threshold steady state blood concentration and occupancy required to elicit a clinically relevant response (>25% reduction in scores on delusions, hallucinations and agitation domains of the Neuropsychiatric Inventory) and extrapyramidal side effects (Simpson Angus Scale scores > 3). Average steady state blood levels were low (71 ± 30 ng/ml), and associated with high D2/3 occupancies (65 ± 8%, caudate; 67 ± 11%, thalamus; 52 ± 11%, putamen). Antipsychotic clinical response occurred at a threshold concentration of 20 ng/ml and D2/3 occupancies of 43% (caudate), 25% (putamen), 43% (thalamus). Extrapyramidal side effects (n = 7) emerged at a threshold concentration of 60 ng/ml, and D2/3 occupancies of 61% (caudate), 49% (putamen) and 69% (thalamus). This study has established that, as in schizophrenia, there is a therapeutic window of D2/3 receptor occupancy for optimal treatment of psychosis in Alzheimer's disease. We have also shown that occupancies within and beyond this window are achieved at very low amisulpride doses in Alzheimer's disease due to higher than anticipated occupancies for a given blood drug concentration. Our findings support a central pharmacokinetic contribution to antipsychotic sensitivity in Alzheimer's disease and implicate the blood-brain barrier, which controls central drug access. Whether high D2/3 receptor occupancies are primarily accounted for by age- or disease-specific blood-brain barrier disruption is unclear, and this is an important future area of future investigation, as it has implications beyond antipsychotic prescribing.