Concentrations Of Risperidone Research Articles

Effect of concomitant use of yokukansan on steady-state blood concentrations of donepezil and risperidone in real-world clinical practice.

Yokukansan is one of the most frequently used herbal medicines that can improve the behavioral and psychological symptoms of dementia. In this exploratory study, we investigated whether yokukansan affects the steady-state blood concentrations of donepezil, risperidone, and the major metabolites of both drugs in a real-world clinical setting. A non-randomized, open-label, single-arm study examining drug-drug interactions was conducted. Fifteen dementia patients taking donepezil for at least 4 weeks and eight schizophrenia patients taking risperidone for at least 2 weeks were orally administered 2.5 g of yokukansan three times a day before or between meals, and blood samples were collected before and 8 weeks after starting co-treatment with yokukansan. Plasma concentrations of donepezil, risperidone, and each metabolite were measured using high-performance liquid chromatography-tandem mass spectrometry and compared before and after the 8-week administration of yokukansan. The plasma concentrations of donepezil and its metabolites (6-O-desmethyl-donepezil, 5-O-desmethyl-donepezil, and donepezil-N-oxide), risperidone, and its metabolite paliperidone did not differ before and after the 8-week treatment with yokukansan. The findings of this study show that the concomitant use of yokukansan may have little clinical impact on the steady-state blood levels of donepezil and risperidone in patients with dementia or schizophrenia.

Relationship between plasma risperidone concentrations and clinical features in chronic schizophrenic patients in China.

Prior studies have noted great variability in the plasma levels of risperidone (RIS). Plasma concentrations of RIS and its active moiety are highly variable and depend on absorption, metabolism, and other predictors of metabolic dysregulation; however, these factors are poorly understood and the association between metabolic change and change in psychopathology is uncertain. To ascertain the characteristics of chronic schizophrenic patients treated with RIS, and to assess their relationship with plasma RIS levels. This was a descriptive cross-sectional study of 50 patients with a diagnosis of schizophrenic psychosis treated with RIS in a psychiatric service. The plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone were determined by high performance liquid chromatography. The patients' demographic and clinical characteristics, and psychopathologies were assessed, and the associations between clinical variables and plasma levels of RIS were explored. Male patients received higher doses of RIS than female ones, but plasma concentrations of RIS and risperidone + 9-hydroxyrisperidone (active moiety) were higher in female patients. Age and the mean scores of the general psychopathology subscale of the Positive and Negative Syndrome Scale (PANSS) were significantly positively correlated with plasma concentrations of risperidone + 9-hydroxyrisperidone adjusted for weight and dose in all 50 subjects. In male subjects, we found a statistically significant positive correlation between the concentrations of risperidone + 9-hydroxyrisperidone in plasma/(dose × kg) and age, mean PANSS negative subscale scores, mean PANSS general psychopathology subscale scores, and mean PANSS total scores. Long-term use of RIS should be closely monitored in older patients and females to minimize the risk of high concentrations which could induce side effects.

The Frequency of CYP2D6 and CYP3A4/5 Genotypes and The Impact of Their Allele Translation and Phenoconversion-Predicted Enzyme Activity on Risperidone Pharmacokinetics in Saudi Children with Autism.

Data on the role of CYP2D6 and CYP3A4/5 polymorphisms in relation to risperidone (RIS) pharmacokinetics (PK) in children are relatively limited and inconsistent. This is partially attributable to the limited coverage of CYP2D6 and CYP3A4/5 metabolizer phenotypes, particularly those of poor and ultrarapid metabolizers (PMs and UMs), which has led to calls for studies of populations with a non-European background that may carry variants that are less frequent in Europeans. Children ≤ 18years old with at least 8weeks of a RIS-based regimen were recruited from three autism centers in Riyadh, Saudi Arabia. The primary outcomes measured were plasma concentrations of RIS and 9-hydroxyrisperidone (9-OH-RIS) and their dose-adjusted (C/D) ratios as a function of phenotypes and activity score (AS). For accurate DNA genotyping, targeted pharmacogenomic testing with the Axiom PharmacoFocus Array was performed via examination of a broad collection of probesets targeting CYP2D6 and CYP3A4/5 variants. The frequency of genotypes/phenotypes and the impact of their allele translation and phenoconversion-predicted enzyme activity were examined. The final cohort included 83 individuals. The most common CYP2D6 phenotype in our population was normal metabolizers (NMs, 66.3%). Inconsistent with some previous studies, the three phenotypes of intermediate metabolizers (IMs), NMs, and UMs were significantly different in terms of RIS concentration, the RIS/9-OH-RIS ratio, the RIS C/D ratio and the 9-OH-RIS C/D ratio. According to AS analyses, there were statistically significant differences in the RIS concentration (P = 0.013), RIS/9-OH-RIS ratio (P < 0.001) and RIS C/D ratio (P = 0.030) when patients were categorized into AS ≤ 1 vs. AS > 1. None of the CYP3A4/5 star allele translated phenotypes revealed a significant influence on any of the RIS PK parameters. Notably, neither CYP2D6 nor CYP3A4/5 phenotyping demonstrated a significant impact on the total active moiety, suggesting that other gene variants could modulate RIS PK. The study confirmed the previously reported partial impact of the CYP2D6 gene on RIS PK. However, future studies using contemporary genotyping techniques targeting a wide range of variants in other candidate genes must be conducted to further examine their interactive effects on RIS PK and the clinical response.

Factors influencing concentrations of risperidone and 9-hydroxyrisperidone in psychiatric outpatients taking immediate-release formulations of risperidone.

To analyze the factors affecting the concentrations of the active moiety of risperidone (RIS) and its active metabolite 9-hydroxyrisperidone (9-OH-RIS) in psychiatric outpatients taking immediate-release formulations. This is a retrospective study on the therapeutic drug monitoring (TDM) data regarding RIS and 9-OH-RIS in adult psychiatric outpatients. TDM data with simultaneous RIS and 9-OH-RIS monitoring from March 2018 to February 2020 and relevant medical records (including dosage, dosage form, sex, age, diagnosis, combined medication, and comorbid disease) from 399 adult psychiatric outpatients (223 males and 176 females) were included in this study. The daily dose of RIS was 5.56±2.05mg, the concentration of total active moiety was 42.35±25.46ng/mL, and the dose-adjusted plasma concentration (C/D) of active moiety was 7.83±3.87 (ng/ml)/(mg/day). Dose, sex, and age were identified as important factors influencing concentrations of RIS and 9-OH-RIS in adult psychiatric outpatients. Individualized medication adjustments should be made according to the specific conditions of psychiatric outpatients. The findings strongly support the use of TDM to guide dosing decisions in psychiatric outpatients taking RIS.

Preparation and Physicochemical Evaluation of Injectable Sustained-Release Risperidone by Lipid Liquid Crystal Vehicle

Introduction: Risperidone is a highly effective medicine in patients with mental disorders. Since maintaining blood concentrations of risperidone within the therapeutic index is pivotal during treatment, these patients should receive medication daily and continuously. Method: In this study, an optimal lipid liquid crystal was designed according to the maximum release for 60 days based on different ratios of phosphatidylcholine (PC) to sorbitan monooleate (PC:SMO), tween 80 (w/w%), and tocopherol acetate (w/w%) using Design Expert software with the Central Composite Design (CCD) method. Release evaluations were conducted in vitro to compare the effects of lipid liquid crystal and Risperdal CONSTA®. The structure evaluation was also tested using polarized electron microscopy and in vitro assessment via cell culture. Results: The optimal formulation was selected based on the maximum release (100%) of the drug obtained within 2 months with a PC: SMO ratio of 58.6%, tween 0.82% (w/w), and tocopherol acetate 3.6% (w/w). A hexagonal mesophase with a dihedral structure was observed in the liquid crystal structure. No toxicity was observed in the cell culture test. Conclusion: The comparison of the results of in vitro studies of the liquid crystal formulation containing risperidone and the commercial formulation, Risperdal CONSTA®, showed that the liquid crystal system provides better and more uniform drug release for 60 days. Therefore, it can increase patient compliance and ease the problems of oral administration

Development and validation of a reverse phase High Performance Liquid Chromatographic method, using standard addition calibration, for determination of risperidone in human plasma

Risperidone is a drug of choice in the management of psychosis and high performance liquid chromatography (HPLC) is regarded as the most sensitive and accurate method for quantitative analysis of risperidone, as well as other drugs having low plasma concentrations in biological fluids. A simple and accurate HPLC method was developed for the determination of risperidone in human plasma using the standard addition calibration technique to augment the weak signals due to low plasma concentrations of risperidone. Risperidone was eluted using isocratic mode with a mobile phase of methanol: acetonitrile (60:40) on a Chemisil ODS C18 column (250 mm×4.6 mm i.d., 5 μ particle size). The sample injection volume, flow rate, column temperature and wavelength of detection were set at 10 µl, 1.0 ml/min, 35 ˚C and 280 nm respectively. The run time for the method was 7 minutes, with risperidone having a retention time of 3.566 minutes. The method was linear within the concentration 10-50 ng/ml (R2= 0.998), with LOD and LOQ of 0.13 and 0.40 ng/ml respectively. The precision and relative error was 3.44 % and 3.38 % respectively. The developed method can be employed in the quantitative determination of risperidone in pharmacokinetic and bioequivalence studies.

External Evaluation of Risperidone Population Pharmacokinetic Models Using Opportunistic Pediatric Data.

Risperidone is approved to treat schizophrenia in adolescents and autistic disorder and bipolar mania in children and adolescents. It is also used off-label in younger children for various psychiatric disorders. Several population pharmacokinetic models of risperidone and 9-OH-risperidone have been published. The objectives of this study were to assess whether opportunistically collected pediatric data can be used to evaluate risperidone population pharmacokinetic models externally and to identify a robust model for precision dosing in children. A total of 103 concentrations of risperidone and 112 concentrations of 9-OH-risperidone, collected from 62 pediatric patients (0.16–16.8 years of age), were used in the present study. The predictive performance of five published population pharmacokinetic models (four joint parent-metabolite models and one parent only) was assessed for accuracy and precision of the predictions using statistical criteria, goodness of fit plots, prediction-corrected visual predictive checks (pcVPCs), and normalized prediction distribution errors (NPDEs). The tested models produced similarly precise predictions (Root Mean Square Error [RMSE]) ranging from 0.021 to 0.027 nmol/ml for risperidone and 0.053–0.065 nmol/ml for 9-OH-risperidone). However, one of the models (a one-compartment mixture model with clearance estimated for three subpopulations) developed with a rich dataset presented fewer biases (Mean Percent Error [MPE, %] of 1.0% vs. 101.4, 146.9, 260.4, and 292.4%) for risperidone. In contrast, a model developed with fewer data and a more similar population to the one used for the external evaluation presented fewer biases for 9-OH-risperidone (MPE: 17% vs. 69.9, 47.8, and 82.9%). None of the models evaluated seemed to be generalizable to the population used in this analysis. All the models had a modest predictive performance, potentially suggesting that sources of inter-individual variability were not entirely captured and that opportunistic data from a highly heterogeneous population are likely not the most appropriate data to evaluate risperidone models externally.

Comprehensive DNA Methylation Analysis of Human Neuroblastoma Cells Treated With Haloperidol and Risperidone.

Accumulating evidence suggests that the epigenetic alterations induced by antipsychotics contribute to the therapeutic efficacy. However, global and site-specific epigenetic changes by antipsychotics and those shared by different classes of antipsychotics remain poorly understood. We conducted a comprehensive DNA methylation analysis of human neuroblastoma cells cultured with antipsychotics. The cells were cultured with low and high concentrations of haloperidol or risperidone for 8 days. DNA methylation assay was performed with the Illumina HumanMethylation450 BeadChip. We found that both haloperidol and risperidone tended to cause hypermethylation changes and showed similar DNA methylation changes closely related to neuronal functions. A total of 294 differentially methylated probes (DMPs), including 197 hypermethylated and 97 hypomethylated DMPs, were identified with both haloperidol and risperidone treatment. Gene ontology analysis of the hypermethylated probe-associated genes showed enrichment of genes related to the regulation of neurotransmitter receptor activity and lipoprotein lipase activity. Pathway analysis identified that among the DMP-associated genes, SHANK1 and SHANK2 were the major genes in the neuropsychiatric disorder-related pathways. Our data would be valuable for understanding the mechanisms of action of antipsychotics from an epigenetic viewpoint.

Clozapine affects the pharmacokinetics of risperidone and inhibits its metabolism and P-glycoprotein–mediated transport in vivo and in vitro: A safety attention to antipsychotic polypharmacy with clozapine and risperidone

Antipsychotic polypharmacy (APP), as one maintenance treatment strategy in patients with schizophrenia, has gained popularity in real-world clinical settings. Risperidone (RIS) and clozapine (CLZ) are the most commonly prescribed second-generation antipsychotics, and they are often used in combination as APP. In this study, the pharmacokinetics of RIS and CLZ in rats were examined after co-administration to explore the reliability and rationality of co-medication with RIS and CLZ. In addition, the effects of CLZ on RIS metabolism and transport in vitro were investigated. The results illustrated that in the 7-day continuous administration test in rats, when co-administered with CLZ, the area under curve and peak concentrations of RIS were increased by 2.2- and 3.1-fold at the first dose, respectively, increased by 3.4- and 6.2-fold at the last dose, respectively. The metabolite-to-parent ratio of RIS was approximately 22% and 33% lower than those of RIS alone group at the first and last doses, respectively. Moreover, CLZ significantly increased RIS concentrations in the brain (3.0–4.8 folds) and cerebrospinal fluid (2.1–3.5 folds) in rats, which was slightly lower than the impact of verapamil on RIS after co-medication. Experiments in vitro indicated that CLZ competitively inhibited the conversion of RIS to 9-hydroxy-RIS with the inhibition constants of 1.36 and 3.0 μM in rat and human liver microsomes, respectively. Furthermore, the efflux ratio of RIS in Caco-2 monolayers was significantly reduced by CLZ at 1 μM. Hence, CLZ may affect the exposure of RIS by inhibiting its metabolism and P-glycoprotein-mediated transport. These findings highlighted that APP with RIS and CLZ might increase the plasma concentrations of RIS and 9-hydroxy-RIS beyond the safety ranges and cause toxic side effects.

Monitoring of antipsychotic plasma levels in the assessment of poor response and nonadherence to antipsychotics in delusional disorder

IntroductionOver the last decades, antipsychotic plasma levels have been used to evaluate therapeutic response, adherence and safety of antipsychotics in schizophrenia. Their clinical utility in delusional disorder (DD) has been poorly studied.ObjectivesTo investigate the relationship between plasma concentrations of risperidone (R), 9-OH-risperidone (9-OH-R) and olanzapine (OLZ), and clinical outcomes in DD.MethodsCase-series of inpatients and outpatients with DD receiving treatment with risperidone (n=19) or olanzapine (n=2). Determination of R, 9-OH-R (active metabolite) and OLZ levels were obtained by high-performance liquid chromatography with electrochemical detection. Clinical variables such as treatment response or adverse events were recorded for all patients. These variables were correlated with two plasmatic ratios in patients treated with R: R:9-OH-R concentration ratio and total concentration-to-dose (C: D) ratio, indicating CYP2D6 activity and R elimination respectively.ResultsTwenty-one patients were included: inpatients (n=10) and outpatients (n=11). Dose range: R, 1-6 mg/day; OLZ, 5-10 mg/day. Three outpatients (R, n=2; OLZ, n=1) presented antipsychotic levels under the detection limit (non-adherence). All R patients showed CYP2D6 activity (R: 9-OH-R ratio &lt;1). Eight patients presented C: D &gt; 14, indicating a reduction of R elimination, which was associated with poor clinical response (n=3), adverse events (n=3) and no clinical relevance (n=2). OLZ (n=2), no association between levels and clinical outcomes.ConclusionsThe determination of antipsychotic plasma levels may be of clinical utility in the assessment of treatment resistance, antipsychotic-adverse events or non-adherence in inpatients or outpatients with DD. Therapeutic drug monitoring should be further studied in future works.DisclosureAGR has received honoraria, registration for congresses and/or travel costs from Janssen, Lundbeck-Otsuka and Angelini.

Relationship between CYP2D6 genotype, activity score and phenotype in a pediatric Thai population treated with risperidone

Recently, the Clinical Pharmacogenetics Implementation Consortium (CPIC) have revised recommendations for the translation of CYP2D6 genotype to phenotype. Changes affect phenotype grouping, as well as the value used to calculate activity score for the CYP2D6*10 allele to better reflect the substantially decreased activity of this allele which is the most frequent allele found in Asian populations. This study aimed to evaluate whether the lower value for CYP2D6*10 as recommended, and the revised phenotype groupings improve the relationship between CYP2D6 genotype and risperidone measures. One hundred and ninety-nine children and adolescents with autism treated with a risperidone-based regimen for at least four weeks were included. CYP2D6 genotype was determined using the Luminex xTAG CYP2D6 Kit assay and translated into phenotype using different translation methods. Plasma concentrations of risperidone and 9-hydroxyrisperidone were measured using LC/MS/MS. Plasma levels of risperidone, risperidone concentration/dose ratio, and risperidone/9-hydroxyrisperidone ratio in patients with an activity score < 1 were significantly higher than those ≥ 1 (P value < 0.001 for all three parameters). Plasma risperidone levels and risperidone concentration/dose ratios were significantly higher in intermediate metabolizers (defined as AS = 0.25–0.75) than normal metabolizer (defined as AS = 1–2) patients (1.44 vs. 0.23 ng/ml, P < 0.001 and 1.63 vs. 0.29 ng/ml/ng, P < 0.001, respectively) as well as risperidone/9-hydroxyrisperidone ratio (0.20 vs. 0.04, P < 0.001). This is the first study in an Asian population utilizing the revised CPIC-recommended method for translating the CYP2D6 genotype to phenotype. In addition to validating that CYP2D6 genetic variation significantly impacts risperidone metabolism, we demonstrated that revised value for the CYP2D6*10 was superior for genotype to phenotype translation. However, at least for risperidone, subjects with an activity score of 1 presented as phenotypic normal, and not intermediate metabolizers, suggesting that phenotype classification is substrate dependent.

Effect of CYP2D6 polymorphisms on plasma concentration and therapeutic effect of risperidone

BackgroundThis study aimed to investigate the influence of CYP2D6 polymorphisms on risperidone plasma concentrations in patients with schizophrenia. Based on pharmacogenomics, we examined whether plasma concentration of risperidone is associated with clinical response and adverse side-effects.MethodsWe recruited patients with chronic schizophrenia who were then treated with risperidone. The CYP2D6 genotypes were determined using targeted sequencing. All high-frequency mutation sites of the nine exons of the gene were assayed in the present study. Plasma concentrations of risperidone and 9-hydroxyrisperidone (9-OH-RIS) were measured using high-performance liquid chromatography (HPLC). Psychiatric symptoms were monitored using The Positive and Negative Syndrome Scale (PANSS), Brief Psychiatric Rating Scale (BPRS), and Clinical Global Impression (CGI). Adverse effects were evaluated using the Barnes Akathisia Scale (BAS) and Extrapyramidal Symptom Rating Scale (ESRS). Follow-up visits were scheduled at weeks 2,4, and 8 after treatment initiation.ResultsAmong the 76 patients, 100 C > T (rs1065852), 1038 C > T (rs1081003), 1662 G > C (rs1058164), 2851 C > T (rs16947), and 4181G > C (rs1135840) variants were detected. The most common allele was CYP2D6*10 (81.6%), whereas CYP2D6*2 (9.2%) and CYP2D6*5 (17.1%) were relatively rare. Plasma levels of risperidone and the risperidone/9-OH risperidone ratio (R/9-OH) were significantly increased in individuals with CYP2D6*10 (P < 0.05). The change in PANSS score, weight, high-density lipoprotein (HDL) level, prolactin (PRL) level, and ESRS were significantly different from baseline, between the different genotypes (P < 0.01). Moreover, individuals with CYP2D6*10 homozygous (TT) mutations were associated with higher risperidone concentration and R/9-OH ratio than those with heterozygous mutations (CT) (P < 0.01). A change from baseline in BPRS scores was observed only during week 8 and was different between heterozygous and homozygous mutations. As for the C2851T polymorphism, the incidence of adverse metabolic effects was significantly different between the C/C and C/T genotypes (P < 0.01). Regarding the G4181C polymorphisms, the changes from baseline in GLU and TG, were different between the C/C and C/G genotypes (P < 0.01).ConclusionsThe genotype of CYP2D6 significantly influences the plasma concentration of risperidone and may subsequently influence the adverse side-effects following risperidone treatment, while also exerting a slight influence on clinical outcomes.

Towards safer risperidone prescribing in Alzheimer's disease.

In the treatment of psychosis, agitation and aggression in Alzheimer's disease, guidelines emphasise the need to 'use the lowest possible dose' of antipsychotic drugs, but provide no information on optimal dosing. This analysis investigated the pharmacokinetic profiles of risperidone and 9-hydroxy (OH)-risperidone, and how these related to treatment-emergent extrapyramidal side-effects (EPS), using data from The Clinical Antipsychotic Trials of Intervention Effectiveness in Alzheimer's Disease study (Clinicaltrials.gov identifier: NCT00015548). A statistical model, which described the concentration-time course of risperidone and 9-OH-risperidone, was used to predict peak, trough and average concentrations of risperidone, 9-OH-risperidone and 'active moiety' (combined concentrations) (n = 108 participants). Logistic regression was used to investigate the associations of pharmacokinetic biomarkers with EPS. Model-based predictions were used to simulate the dose adjustments needed to avoid EPS. The model showed an age-related reduction in risperidone clearance (P < 0.0001), reduced renal elimination of 9-OH-risperidone (elimination half-life 27 h), and slower active moiety clearance in 22% of patients, (concentration-to-dose ratio: 20.2 (s.d. = 7.2) v. 7.6 (s.d. = 4.9) ng/mL per mg/day, Mann-Whitney U-test, P < 0.0001). Higher trough 9-OH-risperidone and active moiety concentrations (P < 0.0001) and lower Mini-Mental State Examination (MMSE) scores (P < 0.0001), were associated with EPS. Model-based predictions suggest the optimum dose ranged from 0.25 mg/day (85 years, MMSE of 5), to 1 mg/day (75 years, MMSE of 15), with alternate day dosing required for those with slower drug clearance. Our findings argue for age- and MMSE-related dose adjustments and suggest that a single measure of the concentration-to-dose ratio could be used to identify those with slower drug clearance.

Impact of Body Mass Index on Serum Concentrations of Antidepressants and Antipsychotics.

Rates of overweight and obesity are higher in patients suffering from psychiatric disorders than in the general population. Body composition and enzyme functions are affected by overweight, and consequently, the pharmacokinetics of drugs may vary in overweight patients. Thus, overweight and obesity are important factors in psychiatric disorders and their treatment. This analysis aimed to investigate the impact of body mass index (BMI) on serum concentrations of the antidepressant drugs amitriptyline, doxepin, escitalopram, mirtazapine, and venlafaxine, and the antipsychotic drugs clozapine, quetiapine, and risperidone, taking into account the following confounding parameters: age, sex, and smoking habit. Inpatients and outpatients (N = 1657) who took at least one of the target drugs were included in this retrospective analysis. Serum concentrations of the target drugs and their metabolites were determined at the Department of Psychiatry, Psychosomatics, and Psychotherapy of the University Hospital of Würzburg during routine therapeutic drug monitoring (January 2009-December 2010), which was performed in the morning (trough level) at steady state. Dose-corrected serum concentrations (CD) of the active moiety of doxepin and venlafaxine and of O-desmethylvenlafaxine were negatively associated with BMI (partial Pearson correlation, R = -0.267, P = 0.002; R = -0.206, P ≤ 0.001; R = -0.258, P ≤ 0.001), and the CDs were different in normal weight, overweight, and obese patients (analysis of covariance, P = 0.004, P < 0.001, P ≤ 0.001). No association was found between BMI and serum concentrations of amitriptyline, escitalopram, mirtazapine, clozapine, quetiapine, and risperidone. In obese patients, higher doses of doxepin and venlafaxine are necessary to achieve similar serum concentrations as in normal weight patients and to avoid treatment-resistant depression.

Modelling Age-Related Changes in the Pharmacokinetics of Risperidone and 9-Hydroxyrisperidone in Different CYP2D6 Phenotypes Using a Physiologically Based Pharmacokinetic Approach

PurposeDose-optimization strategies for risperidone are gaining in importance, especially in the elderly. Based on the genetic polymorphism of cytochrome P 450 (CYP) 2D6 genetically and age-related changes cause differences in the pharmacokinetics of risperidone and 9-hydroxyrisperidone. The goal of the study was to develop physiologically based pharmacokinetic (PBPK) models for the elderly aged 65+ years. Additionally, CYP2D6 phenotyping using metabolic ratio were applied and different pharmacokinetic parameter for different age classes predicted.MethodsPlasma concentrations of risperidone and 9-hydroxyrisperidone were used to phenotype 17 geriatric inpatients treated under naturalistic conditions. For this purpose, PBPK models were developed to examine age-related changes in the pharmacokinetics between CYP2D6 extensive metabolizer, intermediate metabolizer, poor metabolizer, (PM) and ultra-rapid metabolizer.ResultsPBPK-based metabolic ratio was able to predict different CYP2D6 phenotypes during steady-state. One inpatient was identified as a potential PM, showing a metabolic ratio of 3.39. About 88.2% of all predicted plasma concentrations of the inpatients were within the 2-fold error range. Overall, age-related changes of the pharmacokinetics in the elderly were mainly observed in Cmax and AUC. Comparing a population of young adults with the oldest-old, Cmax of risperidone increased with 24–44% and for 9-hydroxyrisperidone with 35–37%.ConclusionsMetabolic ratio combined with PBPK modelling can provide a powerful tool to identify potential CYP2D6 PM during therapeutic drug monitoring. Based on genetic, anatomical and physiological changes during aging, PBPK models ultimately support decision-making regarding dose-optimization strategies to ensure the best therapy for each patient over the age of 65 years.

Plasma Risperidone-related Measures in Children and Adolescents with Oppositional Defiant/Conduct Disorders

ObjectiveTherapeutic drug monitoring helps clinicians in choosing the right drug and adjust its dose in specific patients. To this end, we aimed to assess time patterns of risperidone and its metabolite, 9-hydroxyrisperidone, in children and adolescents with oppositional defiant and/or conduct disorder.MethodsWe measured plasma concentrations of risperidone and 9-hydroxyrisperidone, their sum (active moiety, AM) and ratio, as well as plasma concentrations corrected for daily dose (C/D), from 140 children/adolescents with the above-mentioned disorders. We used Student’s t test to compare females versus males, patients under versus over 16-year-old, patients with lower versus higher than the median body weight, and patients with lower versus higher than the median body mass index (BMI). Two mixed-effects logistic regression models were fitted for risperidone/9-hydroxyrisperidone ratio and AM, respectively, by considering risperidone daily dose and patients’ demographic characteristics.ResultsFemales had higher 9-hydroxyrisperidone and AM plasma concentrations than males (p = 0.004 and p = 0.034). Younger patients had lower risperidone plasma concentration and risperidone/9-hydroxyrisperidone ratio (p = 0.02 and p = 0.021), but higher C/D 9-hydroxyrisperidone and AM than older patients (p = 0.013 and p = 0.043). Lower-weight patients had lower plasma risperidone and risperidone/9-hydroxyrisperidone ratio (p = 0.014 and p = 0.019), but higher C/D 9-hydroxyrisperidone concentration than heavier patients (p = 0.03). All these results could be accounted for by daily dose. Patients with lower and higher BMI did not differ significantly. Regression analyses showed that only risperidone daily dose predicted risperidone/9-hydroxyrisperidone ratio, whereas risperidone daily dose, sex, and age predicted AM.ConclusionClinicians prescribing risperidone need to consider sex, age, and weight, but not BMI when adjusting daily doses.

Influence of Kidney Function on Serum Risperidone Concentrations in Patients Treated With Risperidone.

Risperidone is one of the most commonly prescribed antipsychotics worldwide. Its main metabolite, 9-hydroxyrisperidone (9-OH-RIS), is excreted renally. The present study examined the relationship of kidney function and serum risperidone concentrations in a large sample of risperidone-treated patients. Serum concentrations of risperidone and its active metabolite 9-OH-RIS, as well as creatinine concentrations, from which glomerular filtration rates (GFRs) were estimated, were determined in 175 risperidone-medicated patients (75 female, 100 male). Data were collected between July 2013 and December 2016. Patients were clustered in 4 groups according to their estimated GFR (eGFR) (30-60; > 60-90; > 90-120; and > 120 mL/min/1.73 m²), and serum concentrations of risperidone and 9-OH-RIS and their sum (active moiety [AM]) were compared groupwise. Additionally, serum concentrations were correlated with kidney function. Dose-corrected AM and dose-corrected 9-OH-RIS concentrations were significantly higher in patients with an eGFR of 30-60 mL/min/1.73 m² than in patients with an eGFR > 90-120 mL/min/1.73 m² (P < .001 for dose-corrected AM and P = .001 for dose-corrected 9-OH-RIS) or > 120 mL/min/1.73 m² (P = .036 and .021, respectively). Dose-corrected AM levels were more than doubled in the 30-60 mL/min/1.73 m² group compared to the > 90-120 mL/min/1.73 m² group (mean ± SD = 22.2 ± 14.0 [ng/mL]/[mg/d] vs 10.1 ± 7.7 [ng/mL]/[mg/d]). In the total group, eGFR and dose-corrected 9-OH-RIS and dose-corrected AM were weakly but statistically significantly correlated (Spearman rank correlation coefficient [Rs] = -0.2, P = .004, and Rs = -0.17, P = .01, respectively). Kidney function is an important determinant of risperidone clearance. These data suggest reducing the risperidone dose by 50% in patients with a GFR below 60 mL/min.

Physiologically Based Pharmacokinetic Modelling to Describe the Pharmacokinetics of Risperidone and 9-Hydroxyrisperidone According to Cytochrome P450 2D6 Phenotypes.

The genetic polymorphism of cytochrome P450 (CYP) 2D6 is characterized by an excessive impact on positive and adverse drug reactions to antipsychotics, such as risperidone. Consequently, the pharmacokinetics of the drug and metabolite can be substantially altered and exhibit a high variability between the different phenotypes. The goal of this study was to develop a physiologically based pharmacokinetic (PBPK) model considering the CYP2D6 genetic polymorphism for risperidone and 9-hydroxyrisperidone (9-OH-RIS) taking CYP3A4 into account. Additionally, risperidone dose adjustments, which would compensate for genetically caused differences in the plasma concentrations of the active moiety (sum of risperidone and 9-OH-RIS) were calculated. Based on available knowledge about risperidone, 9-OH-RIS, and relevant physiological changes according to different CYP2D6 phenotypes, several PBPK models were built. In addition, an initial model was further evaluated based on the plasma concentrations of risperidone and 9-OH-RIS from a single-dose study including 71 genotyped healthy volunteers treated with 1mg of oral risperidone. PBPK models were able to accurately describe risperidone exposure after single-dose administration, especially in the concentration range ≥ 1µg/L, illustrated by a minimal bias and a good precision. About 90.3% of all weighted residuals versus observed plasma concentrations ≥ 1µg/L were in the ± 30% range. The risperidone/9-OH-RIS ratio increased progressively according to reduced CYP2D6 activity, resulting in a mean ratio of 4.96 for poor metabolizers. Simulations demonstrate that dose adjustment of the drug by - 25% for poor metabolizers and by - 10% for intermediate metabolizers results in a similar exposure to that of extensive metabolizers. Conversely, the risperidone/9-OH-RIS ratio can be used to determine the phenotype of individuals. PBPK modelling can provide a valuable tool to predict the pharmacokinetics of risperidone and 9-OH-RIS in healthy volunteers, according to the different CYP2D6 phenotypes taking CYP3A4 into account. These models are able to ultimately support decision-making regarding dose-optimization strategies, especially for subjects showing lower CYP2D6 activity.

Co-administration of Magnesium Oxide Reduces the Serum Concentration of Hydrophobic Basic Drugs in Patients Treated with Antipsychotic Drugs

Magnesium oxide (MgO) is a widely used laxative. Because many antipsychotic drugs are lipophilic-basic-compounds, their solubility decreases with increasing pH and changes markedly as the pH of the solution approaches their pKa. It is highly important to clarify the effect of co-administration of MgO on the serum drug concentration for effective, safe, and appropriate medication therapy. However, the relationship between MgO administration and the serum concentration of antipsychotic drugs in patients with schizophrenia has not been reported. Therefore, in the present study, we investigated the effect of MgO administration on the concentration of antipsychotic drugs in the blood of patients with schizophrenia. The serum concentrations of biperiden, zotepine, and risperidone were assayed using an LC/MS system. The correlation between the daily dose of MgO and the relative-drug-concentration (rCp) in each patient was examined. As the MgO dose was increased, the risperidone concentration decreased. The correlation coefficient decreased for risperidone, zotepine, and biperiden, in the same order. To clarify the difference in the suppression potency of MgO on the three drugs, the relationship between the physical properties and the correlation coefficients of each drug was carefully examined. A strong correlation was observed between the pKa and the correlation coefficient. Patients with schizophrenia are often prescribed antipsychotic drugs, which have anticholinergic action and tend to suppress gastric acid secretion. We concluded that basic drug absorption might be suppressed due to an increase in the stomach pH following MgO administration. Therefore, MgO co-administration is better to avoid while taking antipsychotic drugs and anticholinergic drugs.

Metabolism of risperidone by CYP2D6 and the presence of drug-induced dopamine supersensitivity psychosis in patients with schizophrenia

High-dose antipsychotic(s) can induce dopamine supersensitivity psychosis in schizophrenia patients. The precise relationship between a drug's blood concentration and the occurrence of dopamine supersensitivity psychosis has not been established. We divided 36 patients with schizophrenia who had undergone treatment mainly with risperidone into two groups: one with normal metabolizing activity of CYP2D6 (n = 15), and the other with lower activity of its variant, CYP2D6*10 (n = 21). The patients' blood concentrations of risperidone and 9-OH-risperidone were measured, and we compared the occurrence of dopamine supersensitivity psychosis episodes between the groups. There was no significant difference in any concentration of risperidone, 9-OH-risperidone, or active moiety between the groups although the with-CYP2D6*10 group had greater variabilities of these parameters compared to the without-CYP2D6*10 group. There was a lower rate of dopamine supersensitivity psychosis episodes in the without-CYP2D6*10 group (4/15, 26.7%) compared to the with-CYP2D6*10 group (11/21, 52.4%), but the difference was not significant. Although our findings were negative, largely because of the small sample size, these results suggest that (1) patients with an impaired functional allele of CYP2D6 may have higher concentrations of risperidone and its active metabolite and that (2) these patients may experience more frequent dopamine supersensitivity psychosis episodes.