Effects of genetic polymorphisms of CYP2D6, CYP3A5, and ABCB1 on the steady-state plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, in Japanese patients with schizophrenia

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialized tools are used. Three tools have been proven useful to personalize drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 50 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimize treatment effects, minimize side effects and ultimately reduce the global burden of diseases, personalized drug treatment has not yet become the standard of care in psychiatry.

Case report: Avoiding intolerance to antipsychotics through a personalized treatment approach based on pharmacogenetics

Introduction

The standard approach to treatment in psychiatry is known as "treatment as usual" (TAU), in which the same types of treatment are administered to a group of patients. TAU often requires numerous dose adjustments and medication changes due to ineffectiveness and/or the occurrence of adverse drug reactions (ADRs). This process is not only time-consuming but also costly. Antipsychotic medications are commonly used to treat various psychiatric disorders such as schizophrenia and mood disorders. Some of the inter-individual differences in efficacy and ADRs observed in psychopharmacotherapy can be explained by genetic variability in the pharmacokinetics and pharmacodynamics of antipsychotics. A better understanding of (in)efficacy and possible ADRs can be achieved by pharmacogenetic analysis of genes involved in the metabolism of antipsychotics. Most psychotropic drugs are metabolized by genetically variable CYP2D6, CYP1A2, CYP3A4, and CYP2C19 enzymes. To demonstrate the utility of pharmacogenetic testing for tailoring antipsychotic treatment, in this paper, we present the case of a patient in whom a pharmacogenetic approach remarkably altered an otherwise intolerant or ineffective conventional TAU with antipsychotics.

Methods

In this case report, we present a 60-year-old patient with psychotic symptoms who suffered from severe extrapyramidal symptoms and a malignant neuroleptic syndrome during treatment with risperidone, fluphenazine, aripiprazole, brexpiprazole, and olanzapine. Therefore, we performed a pharmacogenetic analysis by genotyping common functional variants in genes involved in the pharmacokinetic pathways of prescribed antipsychotics, namely, CYP2D6, CYP3A4, CYP3A5, CYP1A2, ABCB1, and ABCG2. Treatment recommendations for drug-gene pairs were made according to available evidence-based pharmacogenetic recommendations from the Dutch Pharmacogenetics Working Group (DPWG) or Clinical Pharmacogenetics Implementation Consortium (CPIC).

Results

Pharmacogenetic testing revealed a specific metabolic profile and pharmacokinetic phenotype of the patient, which in retrospect provided possible explanations for the observed ADRs. Based on the pharmacogenetic results, the choice of an effective and safe medication proved to be much easier. The psychotic symptoms disappeared after treatment, while the negative symptoms persisted to a lesser extent.

Conclusion

With the case presented, we have shown that taking into account the pharmacogenetic characteristics of the patient can explain the response to antipsychotic treatment and associated side effects. In addition, pharmacogenetic testing enabled an informed choice of the most appropriate drug and optimal dose adjustment. This approach makes it possible to avoid or minimize potentially serious dose-related ADRs and treatment ineffectiveness. However, due to the complexity of psychopathology and the polypharmacy used in this field, it is of great importance to conduct further pharmacokinetic and pharmacogenetic studies to better assess gene-drug and gene-gene-drug interactions.

Towards Precision Medicine in Clinical Practice: Alinity C vs. UHPLC-MS/MS in Plasma Aripiprazole Determination

Therapeutic drug monitoring improves the benefit-risk balance of antipsychotic therapy. Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) is considered the gold-standard method for measuring plasma drug concentrations; however, the Alinity C system has emerged as a promising alternative. This is the first study aimed at comparing UHPLC-MS/MS versus Alinity C in measuring plasma concentrations of aripiprazole and dehydroaripiprazole. A total of 86 plasma samples were analyzed. The active moiety of aripiprazole was measured in 60 samples using both systems and 26 samples were analyzed twice using Alinity C with an intermediate period of 6 months to assess its reproducibility. Spearman's correlation revealed a good association between the two assays (rs = 0.96) and no significance differences were found by McNemar's test when classifying samples between infra-, supra- and therapeutic ranges. Passing-Bablock regression showed a good correlation among methods (rs = 0.93) and a slope of 1.12 indicating a slight tendency of Alinity C to measure higher values than UHPLC-MS/MS. In addition, a good intra-method correlation across the two sequential analyses with Alinity C was obtained (rs = 0.99). Nonetheless, clinical decisions could be different in 15% of the cases depending on the chosen method. No differences were found in active moiety determination by Alinity C depending on the concentration of aripiprazole and dehydroaripiprazole of the samples.

Evidence for Therapeutic Drug Monitoring of Atypical Antipsychotics

Second-generation antipsychotics (SGAs), also known as atypical antipsychotics, are a newer class of antipsychotic drugs used to treat schizophrenia, bipolar disorder, and related psychiatric conditions. The plasma concentration of antipsychotic drugs is a valid measure of the drug at its primary target structure in the brain, and therefore determines the efficacy and safety of these drugs. However, despite the well-known high variability in pharmacokinetics of these substances, psychiatric medication is usually administered in uniform dosage schedules. Therapeutic drug monitoring (TDM), as the specific method that can help personalised medicine in dose adjustment according to the characteristics of the individual patient, minimizing the risk of toxicity, monitoring adherence, and increasing cost-effectiveness in the treatment, thus seems to be an elegant tool to solve this problem. Non-response to therapeutic doses, uncertain adherence to medication, suboptimal tolerability, or pharmacokinetic drug-drug interactions are typical indications for TDM of SGAs. This review aims to summarize an overview of the current knowledge and evidence of the possibilities to tailor the dosage of selected SGAs using TDM, including the necessary pharmacokinetic parameters for personalised pharmacotherapy.

CYP1A2*F Polymorphism Contributes at Least Partially to the Variability of Plasma Levels of Dehydroaripiprazole, an Active Metabolite of Aripiprazole, in Schizophrenic Patients

AIM

The relationship between CYP1A2 polymorphisms and the steady-state plasma levels of aripiprazole and its active metabolite, dehydroaripiprazole, were investigated in Japanese schizophrenic patients.

BACKGROUND

It has been implied that cytochrome P450 (CYP) 1A2 may play a role in the metabo-lism of aripiprazole. Genetic variations in the CYP1A2 gene have been reported.

OBJECTIVE

The authors investigated the relationship between 2 CYP1A2 polymorphisms, CYP1A2*C (-3860G>A) and CYP1A2*F (-163C>A), and the steady-state plasma levels/dose (C/D) ratios of aripiprazole and dehydroaripiprazole in Japanese schizophrenic patients.

METHODS

All 89 subjects (46 males and 43 females) had been receiving 2 fixed daily doses of aripiprazole (24 mg; n=56 and 12 mg: n=33) for more than 2 weeks. No other drugs were used except flunitrazepam and biperiden. The plasma drug levels were determined by LC/MS/MS. These CYP1A2 polymorphisms were detected using polymerase chain reaction analysis.

RESULTS

The mean C/D ratios of dehydroaripiprazole were significantly (P < 0.05) lower in patients with the A/A allele of CYP1A2*F than in those without the allele. No differences were found in the values of aripiprazole and the combination of aripiprazole and dehydroaripiprazole among the CYP1A2*F genotype. There were no differences in the values of aripiprazole, dehydroaripiprazole, or the combination of the 2 compounds among the CYP1A2*C genotype. The absence of the A allele of CYP1A2*F was correlated with the mean C/D ratios of dehydroaripiprazole (standardized partial correlation coefficient = 0.276, P < 0.01) by multiple regression analysis.

CONCLUSION

The findings of this study suggest that the CYP1A2*F polymorphism contributes at least partially to the variability in the steady-state plasma levels of dehydroaripiprazole.

Pharmacogenetics and Schizophrenia-Can Genomics Improve the Treatment with Second-Generation Antipsychotics?

Schizophrenia (SCZ) is a complex psychiatric disorder of multifactorial origin, in which both genetic and environmental factors have an impact on its onset, course, and outcome. Large variability in response and tolerability of medication among individuals makes it difficult to predict the efficacy of a chosen therapeutic method and create universal and precise guidelines for treatment. Pharmacogenetic research allows for the identification of genetic polymorphisms associated with response to a chosen antipsychotic, thus allowing for a more effective and personal approach to treatment. This review focuses on three frequently prescribed second-generation antipsychotics (SGAs), risperidone, olanzapine, and aripiprazole, and aims to analyze the current state and future perspectives in research dedicated to identifying genetic factors associated with antipsychotic response. Multiple alleles of genes involved in pharmacokinetics (particularly isoenzymes of cytochrome P450), as well as variants of genes involved in dopamine, serotonin, and glutamate neurotransmission, have already been identified as ones of significant impact on antipsychotic response. It must, however, be noted that although currently obtained results are promising, trials with bigger study groups and unified protocols are crucial for standardizing methods and determining objective antipsychotic response status.

Understanding inter-individual variability in pharmacokinetics/pharmacodynamics of aripiprazole in children with tic disorders: Individualized administration based on physiological development and CYP2D6 genotypes

Objective: This study aims to develop a combined population pharmacokinetic (PPK) model for aripiprazole (ARI) and its main active metabolite dehydroaripiprazole (DARI) in pediatric patients with tic disorders (TD), to investigate the inter-individual variability caused by physiological and genetic factors in pharmacokinetics of ARI and optimize the dosing regimens for pediatric patients. Methods: A prospective PPK research was performed in Chinese children with TD. Totally 84 patients aged 4.83-17.33 years were obtained for the pharmacokinetic analysis. 27 CYP2D6 and ABCB1 gene alleles were detected. Moreover, the clinical efficacy was evaluated according to reduction rate of Yale Global Tic Severity Scale (YGTSS) score at the 12th week comparing with the baseline. Monte Carlo simulations were used to evaluate and optimize dosing regimens. Results: The PPK model was established to predict the concentrations of ARI and DARI. Body weight and CYP2D6 genotype were the significant covariates affecting the clearance of ARI. The DARI/ARI metabolic ratios (MRs) of AUC24h, Cmin and Cmax at the steady state of results were ultra-rapid metabolizers (UMs) > normal metabolizers (NMs) > intermediated metabolizers (IMs). MRs could be used to distinguish UMs or IMs from other patients. The best predictor of clinical efficacy for TD was the trough concentration of ARI and the cut-off point was 101.636 ng/ml. Conclusion: The pharmacokinetics of ARI and DARI in pediatric TD were significantly influenced by body weight and CYP2D6 genotype. Individualized dosing regimens were recommended for pediatric patients with TD to ensure clinical efficacy.

CYP2D6 pharmacogenetics and phenoconversion in personalized medicine

INTRODUCTION

CYP2D6 contributes to the metabolism of approximately 20-25% of drugs. However, CYP2D6 is highly polymorphic and different alleles can lead to impacts ranging from null to increase in activity. Moreover, there are commonly used drugs that potently inhibit the CYP2D6, thus causing 'phenoconversion' which can convert the genotypic normal metabolizer into phenotypic poor metabolizer. Despite growing literature on the clinical implications of non-normal CYP2D6 genotype and phenoconversion on patient-related outcomes, implementation of CYP2D6 pharmacogenetics and phenoconversion to guide prescribing is rare. This review focuses on providing the clinical importance of CYP2D6 pharmacogenetics and phenoconversion in precision medicine and summarizes the challenges and approaches to implement these into clinical practice.

AREAS COVERED

A literature search was performed using PubMed and clinical studies documenting the effects of CYP2D6 genotypes and/or CYP2D6 inhibitors on pharmacokinetics, pharmacodynamics or treatment outcomes of CYP2D6-metabolized drugs, and studies on implementation challenges and approaches.

EXPERT OPINION

Considering the extent and impact of genetic polymorphisms of CYP2D6, phenoconversion by the comedications, and contribution of CYP2D6 in drug metabolism, CYP2D6 pharmacogenetics is essential to ensure drug safety and efficacy. Utilization of proper guidelines incorporating both CYP2D6 pharmacogenetics and phenoconversion in clinical care assists in optimizing drug therapy.

Effects of CYP2C19 and CYP2D6 gene variants on escitalopram and aripiprazole treatment outcome and serum levels: results from the CAN-BIND 1 study

Cytochrome P450 drug-metabolizing enzymes may contribute to interindividual differences in antidepressant outcomes. We investigated the effects of CYP2C19 and CYP2D6 gene variants on response, tolerability, and serum concentrations. Patients (N = 178) were treated with escitalopram (ESC) from weeks 0-8 (Phase I), and at week 8, either continued ESC if they were responders or were augmented with aripiprazole (ARI) if they were non-responders (<50% reduction in Montgomery-Åsberg Depression Rating Scale from baseline) for weeks 8-16 (Phase II). Our results showed that amongst patients on ESC-Only, CYP2C19 intermediate and poor metabolizers (IM + PMs), with reduced or null enzyme function, trended towards significantly lower symptom improvement during Phase II compared to normal metabolizers (NMs), which was not observed in ESC + ARI. We further showed that CYP2D6 NMs and IM + PMs had a higher likelihood of reporting a treatment-related central nervous system side effect in ESC-Only and ESC + ARI, respectively. The differences in the findings between ESC-Only and ESC + ARI may be due to the altered pharmacokinetics of ESC by ARI coadministration in ESC + ARI. We provided evidence for this postulation when we showed that in ESC-Only, CYP2C19 and CYP2D6 IM + PMs demonstrated significantly higher ESC concentrations at Weeks 10 and 16 compared to NMs. In contrast, ESC + ARI showed an association with CYP2C19 but not with CYP2D6 metabolizer group. Instead, ESC + ARI showed an association between CYP2D6 metabolizer group and ARI metabolite-to-drug ratio suggesting potential competition between ESC and ARI for CYP2D6. Our findings suggest that dosing based on CYP2C19 and CYP2D6 genotyping could improve safety and outcome in patients on ESC monotherapy.

CYP2D6 Genotyping and Antipsychotic-Associated Extrapyramidal Adverse Effects in a Randomized Trial of Aripiprazole Versus Quetiapine Extended Release in Children and Adolescents, Aged 12-17 Years, With First Episode Psychosis

PURPOSE/BACKGROUND

The aim of this study was to examine the association between genetically predicted CYP2D6 phenotypes and extrapyramidal symptoms (EPSs).

METHODS/PROCEDURES

Data from the Tolerability and Efficacy of Antipsychotics trial of adolescents with first-episode psychosis randomized to aripiprazole versus quetiapine extended release were studied. Extrapyramidal symptom assessments included the Simpson-Angus Scale and the Barnes Akathisia Rating Scale. Patients were CYP2D6 genotyped. Plasma concentrations of antipsychotics and antidepressants were analyzed.

FINDINGS/RESULTS

One hundred thirteen youths (age, 12-17 years; males, 30%; antipsychotic naive, 51%) were enrolled. Poor metabolizers had a significantly higher dose-adjusted aripiprazole plasma concentration (±SD) compared with normal metabolizers at week 4 (24.30 ± 6.40 ng/mL per milligram vs 14.85 ± 6.15 ng/mL per milligram; P = 0.019), but not at week 12 (22.15 ± 11.04 ng/mL per milligram vs 14.32 ± 4.52 ng/mL per milligram; P = 0.067). This association was not found in the quetiapine extended release group. No association between CYP2D6 genotype groups and global Barnes Akathisia Rating Scale score or Simpson-Angus Scale score was found in any of the treatment arms.

IMPLICATIONS/CONCLUSIONS

Our results do not support routine use of CYP2D6 testing as a predictor of drug-induced parkinsonism or akathisia risk in clinical settings. Further studies with larger samples of CYP2D6 poor metabolizers are needed.

Genetic Polymorphisms Associated With the Pharmacokinetics, Pharmacodynamics and Adverse Effects of Olanzapine, Aripiprazole and Risperidone

Olanzapine, aripiprazole and risperidone are atypical antipsychotics or neuroleptics widely used for schizophrenia treatment. They induce various adverse drug reactions depending on their mechanisms of action: metabolic effects, such as weight gain and alterations of glucose and lipid metabolism; hyperprolactinemia and extrapyramidal effects, such as tremor, akathisia, dystonia, anxiety and distress. In this review, we listed polymorphisms associated with individual response variability to olanzapine, aripiprazole and risperidone. Olanzapine is mainly metabolized by cytochrome P450 enzymes, CYP1A2 and CYP2D6, whereas aripiprazole and risperidone metabolism is mainly mediated by CYP2D6 and CYP3A4. Polymorphisms in these genes and other enzymes and transporters, such as enzymes from the uridine 5'-diphospho-glucuronosyltransferase (UGT) family and ATP-binding cassette sub-family B member 1 (ABCB1), are associated to differences in pharmacokinetics. The three antipsychotics act on dopamine and serotonin receptors, among others, and several studies found associations between polymorphisms in these genes and variations in the incidence of adverse effects and in the response to the drug. Since olanzapine is metabolized by CYP1A2, a lower starting dose should be considered in patients treated with fluvoxamine or other CYP1A2 inhibitors. Regarding aripiprazole, a reduced dose should be administered in CYP2D6 poor metabolizers (PMs). Additionally, a reduction to a quarter of the normal dose is recommended if the patient is treated with concomitant CYP3A4 inhibitors. Risperidone dosage should be reduced for CYP2D6 PMs and titrated for CYPD6 ultrarapid metabolizers (UMs). Moreover, risperidone dose should be evaluated when a CYP2D6, CYP3A4 or ABCB1 inhibitor is administered concomitantly.

Review of Pharmacokinetics and Pharmacogenetics in Atypical Long-Acting Injectable Antipsychotics

Over the last two decades, pharmacogenetics and pharmacokinetics have been increasingly used in clinical practice in Psychiatry due to the high variability regarding response and side effects of antipsychotic drugs. Specifically, long-acting injectable (LAI) antipsychotics have different pharmacokinetic profile than oral formulations due to their sustained release characteristics. In addition, most of these drugs are metabolized by CYP2D6, whose interindividual genetic variability results in different metabolizer status and, consequently, into different plasma concentrations of the drugs. In this context, there is consistent evidence which supports the use of therapeutic drug monitoring (TDM) along with pharmacogenetic tests to improve safety and efficacy of antipsychotic pharmacotherapy. This comprehensive review aims to compile all the available pharmacokinetic and pharmacogenetic data regarding the three major LAI atypical antipsychotics: risperidone, paliperidone and aripiprazole. On the one hand, CYP2D6 metabolizer status influences the pharmacokinetics of LAI aripiprazole, but this relation remains a matter of debate for LAI risperidone and LAI paliperidone. On the other hand, developed population pharmacokinetic (popPK) models showed the influence of body weight or administration site on the pharmacokinetics of these LAI antipsychotics. The combination of pharmacogenetics and pharmacokinetics (including popPK models) leads to a personalized antipsychotic therapy. In this sense, the optimization of these treatments improves the benefit–risk balance and, consequently, patients’ quality of life.

Effects of the combination of second-generation antipsychotics on serum concentrations of aripiprazole and dehydroaripiprazole in Chinese patients with schizophrenia

Background

Aripiprazole (ARI) is often prescribed alone or in combination with other second-generation antipsychotics (SGAs) to treat patients with schizophrenia. However, this may increase the potential clinical significance of drug–drug interactions. Therapeutic drug monitoring (TDM) is an important and fundamental tool both when administering ARI alone and in combination with other SGAs to monitor ARI pharmacokinetics, adjust the dosage and thereby achieve more effective and safer treatment.

Aims

This study retrospectively investigated the effects of four SGA comedications (clozapine, risperidone, quetiapine (QTP) and olanzapine) and other potential factors (sex, age and ARI dose) on the serum concentrations of ARI and dehydroaripiprazole (DARI) in Chinese patients with schizophrenia using TDM data.

Methods

High-performance liquid chromatography was used to test the serum concentrations of ARI, DARI and ARI+DARI. In addition, steady-state dose-adjusted serum concentrations (ie, concentration-to-dose ratios, C:D ratios) of ARI, DARI and ARI+DARI; sex; age; ARI dose and SGA comedication dose between 299 inpatients with schizophrenia who received ARI or SGA comedication were all collected and analysed. Spearman’s correlation and multiple linear regression analysis were used to evaluate bivariate associations between ARI dose and serum ARI and DARI concentrations and describe the effect of independent variables on serum ARI and DARI concentrations, respectively.

Results

There were significant differences in the C:D ratios of ARI (χ²=−3.21, p=0.001) and ARI+DARI (χ²=−2.50, p=0.01) between the ARI and SGA groups, as well as in the C:D ratios of ARI (χ²=−3.59, p<0.001) and ARI+DARI (χ²=−3.10, p=0.002) between the female patients in the two groups. Of the four SGAs, only QTP had significant effects on the C:D ratios of ARI (Z=−4.12, p<0.001) and ARI+DARI (Z=−3.62, p<0.001) when compared with the ARI group in the whole sample and on the C:D ratios of ARI, DARI and ARI+DARI (Z=−3.96, p<0.001; Z=−2.22, p=0.03; Z=−3.75, p<0.001, respectively) in women when compared with their counterparts in the ARI group.

Conclusion

Comedication with SGAs resulted in lower C:D ratios of ARI and ARI+DARI compared with ARI monotherapy, and comedication with QTP resulted in lower C:D ratios of ARI and ARI+DARI than ARI monotherapy. Despite this statistical significance of our findings, whether the presently observed effect has clinical significance requires exploration by further research. TDM and dosage regulation of ARI should be performed in Chinese inpatients with schizophrenia who are receiving SGA comedication (especially QTP) to maintain a safe and effective dose-adjusted serum concentration of ARI and DARI.

Association of CYP2C19 and CYP2D6 Poor and Intermediate Metabolizer Status With Antidepressant and Antipsychotic Exposure: A Systematic Review and Meta-analysis

IMPORTANCE

Precise estimation of the drug metabolism capacity for individual patients is crucial for adequate dose personalization.

OBJECTIVE

To quantify the difference in the antipsychotic and antidepressant exposure among patients with genetically associated CYP2C19 and CYP2D6 poor (PM), intermediate (IM), and normal (NM) metabolizers.

DATA SOURCES

PubMed, Clinicaltrialsregister.eu, ClinicalTrials.gov, International Clinical Trials Registry Platform, and CENTRAL databases were screened for studies from January 1, 1990, to June 30, 2020, with no language restrictions.

STUDY SELECTION

Two independent reviewers performed study screening and assessed the following inclusion criteria: (1) appropriate CYP2C19 or CYP2D6 genotyping was performed, (2) genotype-based classification into CYP2C19 or CYP2D6 NM, IM, and PM categories was possible, and (3) 3 patients per metabolizer category were available.

DATA EXTRACTION AND SYNTHESIS

The Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines were followed for extracting data and quality, validity, and risk of bias assessments. A fixed-effects model was used for pooling the effect sizes of the included studies.

MAIN OUTCOMES AND MEASURES

Drug exposure was measured as (1) dose-normalized area under the plasma level (time) curve, (2) dose-normalized steady-state plasma level, or (3) reciprocal apparent total drug clearance. The ratio of means (RoM) was calculated by dividing the mean drug exposure for PM, IM, or pooled PM plus IM categories by the mean drug exposure for the NM category.

RESULTS

Based on the data derived from 94 unique studies and 8379 unique individuals, the most profound differences were observed in the patients treated with aripiprazole (CYP2D6 PM plus IM vs NM RoM, 1.48; 95% CI, 1.41-1.57; 12 studies; 1038 patients), haloperidol lactate (CYP2D6 PM vs NM RoM, 1.68; 95% CI, 1.40-2.02; 9 studies; 423 patients), risperidone (CYP2D6 PM plus IM vs NM RoM, 1.36; 95% CI, 1.28-1.44; 23 studies; 1492 patients), escitalopram oxalate (CYP2C19 PM vs NM, RoM, 2.63; 95% CI, 2.40-2.89; 4 studies; 1262 patients), and sertraline hydrochloride (CYP2C19 IM vs NM RoM, 1.38; 95% CI, 1.27-1.51; 3 studies; 917 patients). Exposure differences were also observed for clozapine, quetiapine fumarate, amitriptyline hydrochloride, mirtazapine, nortriptyline hydrochloride, fluoxetine hydrochloride, fluvoxamine maleate, paroxetine hydrochloride, and venlafaxine hydrochloride; however, these differences were marginal, ambiguous, or based on less than 3 independent studies.

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis, the association between CYP2C19/CYP2D6 genotype and drug levels of several psychiatric drugs was quantified with sufficient precision as to be useful as a scientific foundation for CYP2D6/CYP2C19 genotype-based dosing recommendations.

Variations and expression features of CYP2D6 contribute to schizophrenia risk

Genome-wide association studies (GWAS) have successfully identified 145 loci implicated in schizophrenia (SCZ). However, the underlying mechanisms remain largely unknown. Here, we analyze 1497 RNA-seq data in combination with their genotype data and identify SNPs that are associated with expression throughout the genome by dissecting expression features to genes (eGene) and exon-exon junctions (eJunction). Then, we colocalize eGene and eJunction with SCZ GWAS using SMR and fine mapping. Multiple ChIP-seq data and DNA methylation data generated from brain were used for identifying the causal variants. Finally, we used a hypothesis-free (no SCZ risk loci considered) enrichment analysis to determine implicated pathways. We identified 171 genes and eight splicing junctions located within four genes (SNX19, ARL6IP4, APOPT1, and CYP2D6) that potentially contribute to SCZ susceptibility. Among the genes, CYP2D6 is significantly associated with SCZ SNPs in eGene and eJunction. In-depth examination of the CYP2D6 region revealed that a nonsynonymous single nucleotide variant rs16947 is strongly associated with a higher abundance of CYP2D6 exon 3 skipping junctions. While we found rs133377 and other functional SNPs in high linkage disequilibrium with rs16947 (r² = 0.9539), histone acetylation analysis showed they are located within active transcription start sites. Furthermore, our data-driven enrichment analysis showed that CYP2D6 is significantly involved in drug metabolism of codeine, tamoxifen, and citalopram. Our study facilitates an understanding of the genetic architecture of SCZ and provides new drug targets.

Therapeutic drug monitoring of children and adolescents treated with aripiprazole: observational results from routine patient care

Although aripiprazole is one of the most used antipsychotics, knowledge about serum concentrations in children and adolescents is scarce and age-specific therapeutic ranges have not been established yet. Data of a routine therapeutic drug monitoring service were analyzed in order to evaluate the relationship between dose and serum concentration of aripiprazole in children and adolescents. The study also aimed to evaluate whether the therapeutic reference range defined for adults with schizophrenia (100-350 ng/ml) is applicable for minors. Data from 130 patients (aged 7-19 years) treated with aripiprazole for different indications in doses of 2-30 mg/day were evaluated. Patient characteristics, doses, serum concentrations and therapeutic outcome were assessed by standardized measures. A positive mean correlation between body weight-corrected daily dose and aripiprazole concentration was found (r_p = 0.59, p < 0.001) with variation in dose explaining 35% of the variability in serum concentrations. Girls had on average 41% higher dose-corrected concentrations than boys (244.9 versus 173.4 mg/l; p = 0.006). Aripiprazole concentrations did not vary with co-medication (p = 0.22). About 70% of all measured serum concentrations were within the recommended therapeutic range for adults. Using a calculation method in all responding patients with an ICD-10 F2 diagnosis for a rough estimation of a preliminary therapeutic window also demonstrated a similar therapeutic range of aripiprazole in minors (105.9-375.3 ng/ml) than for adults. If confirmed in larger samples and more controlled study designs, these data may contribute to the definition of a therapeutic range of aripiprazole concentrations in children and adolescents.

The effects of aripiprazole and olanzapine on pupillary light reflex and its relationship with pharmacogenetics in a randomized multiple-dose trial

Aims

Pupillography is a noninvasive and cost‐effective method to determine autonomic nerve activity. Genetic variants in cytochrome P450 (CYP), dopamine receptor (DRD2, DRD3), serotonin receptor (HTR2A, HTR2C) and ATP‐binding cassette subfamily B (ABCB1) genes, among others, were previously associated with the pharmacokinetics and pharmacodynamics of antipsychotic drugs. Our aim was to evaluate the effects of aripiprazole and olanzapine on pupillary light reflex related to pharmacogenetics.

Methods

Twenty‐four healthy volunteers receiving 5 oral doses of 10 mg aripiprazole and 5 mg olanzapine tablets were genotyped for 46 polymorphisms by quantitative polymerase chain reaction. Pupil examination was performed by automated pupillometry. Aripiprazole, dehydro‐aripiprazole and olanzapine plasma concentrations were measured by high‐performance liquid chromatography–tandem mass spectrometry.

Results

Aripiprazole affected pupil contraction: it caused dilatation after the administration of the first dose, then caused constriction after each dosing. It induced changes in all pupillometric parameters (P < .05). Olanzapine only altered minimum pupil size (P = .046). Polymorphisms in CYP3A, HTR2A, UGT1A1, DRD2 and ABCB1 affected pupil size, the time of onset of constriction, pupil recovery and constriction velocity. Aripiprazole, dehydro‐aripiprazole and olanzapine pharmacokinetics were significantly affected by polymorphisms in CYP2D6, CYP3A, CYP1A2, ABCB1 and UGT1A1 genes.

Conclusions

In conclusion, aripiprazole and its main metabolite, dehydro‐aripiprazole altered pupil contraction, but olanzapine did not have such an effect. Many polymorphisms may influence pupillometric parameters and several polymorphisms had an effect on aripiprazole, dehydro‐aripiprazole and olanzapine pharmacokinetics. Pupillography could be a useful tool for the determination of autonomic nerve activity during antipsychotic treatment.

Dopamine Receptor Partial Agonists for the Treatment of Bipolar Disorder

Bipolar disorder is a chronic, disabling, and costly illness with frequent relapses and recurrences, high rates of co-morbid conditions, and poor adherence to treatment. Mood stabilizers and antipsychotics are the cornerstones of treatment. Dopamine receptor partial agonists are a novel class of antipsychotic agents with original pharmacodynamic properties. Among them, two have been approved by the US Food and Drug Administration for the treatment of bipolar disorder. Aripiprazole (oral formulation) has been approved as monotherapy for the treatment of manic/mixed episodes in adult and pediatric populations and for maintenance treatment in adults, and as adjunctive treatment to mood stabilizers, for the acute treatment of manic/mixed episodes and for maintenance in adults. An intramuscular formulation of aripiprazole has been approved for the treatment of agitation in mania and a long-acting injectable formulation has been approved as maintenance treatment. In the USA, cariprazine has been approved as monotherapy for the acute treatment of manic/mixed as well as bipolar depressive episodes. Brexpiprazole is not yet approved to treat bipolar disorder. The evidence supporting these indications is reviewed via an analysis of clinical registration trials as well as additional studies, on the basis of a systematic literature search. Further studies dealing with other aspects of bipolar illness are also presented. Aripiprazole and cariprazine are efficacious and generally well tolerated agents that have shown cost effectiveness, and may therefore enrich our therapeutic armamentarium for bipolar illness. Brexpiprazole, which displays an overall promising tolerability profile, deserves further efficacy studies.

Phenoconversion of CYP2D6 by inhibitors modifies aripiprazole exposure

The efficacy of aripiprazole therapy and the risk of adverse reactions are influenced by substantial inter-individual variability in aripiprazole metabolizing capacity. In vitro studies assigned the potential role in aripiprazole metabolism to CYP2D6 and CYP3A enzymes; therefore, the association between the steady-state aripiprazole plasma concentrations and patients' CYP2D6 and CYP3A statuses (CYP2D6, CYP3A4, and CYP3A5 genotypes, and CYP3A4 expression) and/or co-medication with CYP function modifying medications has been investigated in 93 psychiatric patients on stable aripiprazole therapy. The patients' CYP2D6 genotype had a major effect on aripiprazole plasma concentrations, whereas contribution of CYP3A genotypes and CYP3A4 expression to aripiprazole clearance were considered to be minor or negligible. The role of CYP3A4 expression in aripiprazole metabolism did not predominate even in the patients with nonfunctional CYP2D6 alleles. Furthermore, dehydroaripiprazole exposure was also CYP2D6 genotype-dependent. Dehydroaripiprazole concentrations were comparable with aripiprazole levels in patients with functional CYP2D6 alleles, and 35% or 22% of aripiprazole concentrations in patients with one or two non-functional CYP2D6 alleles, respectively. The concomitant intake of CYP2D6 inhibitors, risperidone, metoprolol, or propranolol was found to increase aripiprazole concentrations in patients with at least one wild-type CYP2D6*1 allele. Risperidone and 9-hydroxy-risperidone inhibited both dehydrogenation and hydroxylation of aripiprazole, whereas metoprolol and propranolol blocked merely the formation of the active dehydroaripiprazole metabolite, switching towards the inactivation pathways. Patients' CYP2D6 genotype and co-medication with CYP2D6 inhibitors can be considered to be the major determinants of aripiprazole pharmacokinetics. Taking into account CYP2D6 genotype and co-medication with CYP2D6 inhibitors may improve the outcomes of aripiprazole therapy.

Effect of CYP2D6 genotype on exposure and efficacy of risperidone and aripiprazole: a retrospective, cohort study

BACKGROUND

The polymorphic CYP2D6 enzyme metabolises the antipsychotic drugs risperidone and aripiprazole to their active metabolites, 9OH-risperidone and dehydroaripiprazole. The aim of this study was to quantify the effect of CYP2D6 genetic variability on risperidone and aripiprazole exposure and treatment in a large patient population.

METHODS

We retrospectively obtained patient data from a routine therapeutic drug monitoring database at the Center for Psychopharmacology, Diakonhjemmet Hospital, Oslo, Norway, between Jan 1, 2005, and Oct 15, 2018. Individuals included in our analyses were CYP2D6-genotyped patients treated with risperidone or aripiprazole. Inclusion criteria for measurement of pharmacokinetic parameters (drug and metabolite serum concentrations) were oral administration of risperidone or aripiprazole, information known about prescribed daily dose and comedications, and aged older than 18 years. Exclusion criteria included polypharmacy with drugs known to be CYP2D6 inhibitors or CYP3A4 inducers or inhibitors. Treatment failure was analysed in all patients treated with risperidone or aripiprazole without these criteria. The first endpoint in our analysis was the metabolism of risperidone to 9OH-risperidone and aripiprazole to dehydroaripiprazole, estimated by the log-transformed ratio between the concentrations of metabolite and parent drug (ie, the metabolic ratio for risperidone [9OH-risperidone]/[risperidone] and the metabolic ratio for aripiprazole [dehydroaripiprazole]/[aripiprazole]). Endpoint two was measurement of drug exposure, quantified by the dose-normalised sum of parent drug and active metabolite serum concentrations (ie, active moiety). The third endpoint of treatment failure was measured as the number of patients switched from risperidone or aripiprazole to another antipsychotic drug within 1 year after the last therapeutic drug monitoring analysis of risperidone or aripiprazole. Patient subgroups were defined by CYP2D6 genotype-determined metaboliser status: poor metabolisers, intermediate metabolisers, normal metabolisers, and ultrarapid metabolisers. ANOVA was used to assess the differences in metabolic ratios, active moieties, and daily doses between individual metaboliser categories, and risperidone and aripiprazole therapeutic failures were compared by logistic regression using the normal metaboliser subgroup as a reference.

FINDINGS

1288 risperidone-treated patients and 1334 aripiprazole-treated patients were included in the study, of whom 725 (56%) risperidone-treated and 890 (67%) aripiprazole-treated patients were eligible for the pharmacokinetic analyses. CYP2D6 genotype significantly changed risperidone and aripiprazole metabolism resulting in an approximately 1·6-times and 1·4-times increase in risperidone and aripiprazole active moiety exposure in poor and intermediate metabolisers compared with normal metabolisers, respectively (odds ratios [OR] for the risperidone dose-normalised active moiety concentration 1·568, 95% CI 1·401-1·736, and 1·373, 1·213-1·532; and for the aripiprazole dose-normalised active moiety concentration 1·585, 1·447-1·724, and 1·476, 1·263-1·688, respectively; p<0·0001 for all). Compared with doses for normal metabolisers, clinicians reduced daily doses of risperidone and aripiprazole administered to poor metabolisers by 19% (95% CI 5-35, p=0·010) and 15% (95% CI 1-28, p=0·033) respectively. The incidence of switching from risperidone to another antipsychotic was increased in ultrarapid metabolisers (OR 2·934, 95% CI 1·437-5·989, p=0·003) and poor metabolisers (1·874, 1·128-3·112, p=0·015); by contrast, the incidence of switching from aripiprazole to another antipsychotic was not significantly related to CYP2D6 metaboliser status.

INTERPRETATION

CYP2D6 genotype had a substantial clinical effect on risperidone and aripiprazole exposure and on the therapeutic failure of risperidone. Pre-emptive CYP2D6 genotyping would be valuable for individualising risperidone and aripiprazole dosing and treatment optimisation.

FUNDING

H2020 program U-PGx, The Swedish Research Council, the Swedish Brain foundation, and the South-Eastern Norway Regional Health Authority.

Effects of aripiprazole on pupillometric parameters related to pharmacokinetics and pharmacogenetics after single oral administration to healthy subjects

BACKGROUND

Pupillometry is used for the detection of autonomic dysfunction related to numerous diseases and drug administration. Genetic variants in cytochrome P450 ( CYP2D6, CYP3A4), dopamine receptor ( DRD2, DRD3), serotonin receptor ( HTR2A, HTR2C) and ATP-binding cassette subfamily B ( ABCB1) genes were previously associated with aripiprazole response.

AIMS

Our aim was to evaluate if aripiprazole affects pupil contraction and its relationship with pharmacokinetics and pharmacogenetics.

METHODS

Thirty-two healthy volunteers receiving a 10 mg single oral dose of aripiprazole were genotyped for 15 polymorphisms in ABCB1, CYP2D6, DRD2, DRD3, HTR2A and HTR2C genes by reverse transcription polymerase chain reaction. Aripiprazole and dehydro-aripiprazole plasma concentrations were measured by high-performance liquid chromatography tandem mass spectrometry. Pupil examination was performed by automated pupillometry.

RESULTS

Aripiprazole caused pupil constriction and reached the peak value at C_max. HTR2A rs6313 T allele carriers and HTR2C rs3813929 C/T subjects showed higher maximum constriction velocity and maximum pupil diameter. Besides, Gly/Gly homozygotes for DRD3 rs6280 showed significantly lower maximum constriction velocity values. A/G heterozygotes for DRD2 rs6277 showed higher total time taken by the pupil to recover 75% of the initial resting size values. CYP2D6 intermediate metabolisers showed higher area under the curve, C_max and T_1/2 than extensive metabolisers. ABCB1 G2677T/A A/A homozygotes had greater T_1/2 in comparison with C/C homozygotes. ABCB1 C3435T T allele carriers and C1236T C/T subjects showed greater area under the curve than C/C homozygotes.

CONCLUSIONS

Aripiprazole affects pupil contraction, which could be a secondary effect through dopamine and serotonin receptors. Pupillometry could be a useful tool to assess autonomic nervous system activity during antipsychotic treatment.

Usefulness of Pharmacogenetic Analysis in Psychiatric Clinical Practice: A Case Report

There are many factors involved in the effectiveness and efficiency of psychiatric drug treatment. One of them is psychotropic drug metabolism, which takes place mostly in the liver through the P450 enzyme system. However, there are genotypic variants of this system’s enzymes that can directly affect both the efficacy and the onset of side effects of a given therapeutic regimen. These genotypic changes could partly explain the lack of efficacy of treatment in certain patients. We report the case of a patient diagnosed with bipolar type I disorder that presented multiple and frequent manic episodes in which the efficacy and tolerability of several pharmacological regimens with mood stabilizers and antipsychotics was scarce. The choice of medical treatment should be based on its efficacy and side effect profile. This decision can be made more accurately using the information provided by pharmacogenetic analysis. This case illustrates the importance of pharmacogenetic studies in clinical practice. The results of pharmacogenetic analysis helped to decide on a better treatment plan to achieve clinical improvement and reduce drug-induced adverse effects.

Effects of ABCB1 gene polymorphisms on autonomic nervous system activity during atypical antipsychotic treatment in schizophrenia

BACKGROUND

There are interindividual differences in the adverse effects of atypical antipsychotics, which include autonomic nervous system (ANS) dysfunction. Accordingly, to clarify the interindividual differences in the adverse effects of specific atypical antipsychotics in schizophrenia, we investigated the association between ANS dysfunction and ATP-binding cassette transport sub-family B member 1 (ABCB1) gene polymorphisms in patients with schizophrenia.

METHODS

In total, 233 Japanese patients with schizophrenia participated in this study. All of the participants received an atypical antipsychotic as monotherapy: 89 participants received risperidone, 69 olanzapine, 48 aripiprazole, and 27 quetiapine. ANS activity was assessed by means of a power spectral analysis of heart rate variability. Four single nucleotide polymorphisms (SNPs) in ABCB1 (rs1045642, rs1128503, rs2032582, and rs2235048) were genotyped using the TaqMan method.

RESULTS

For aripiprazole, sympathetic and total autonomic nervous activities were significantly lower in the rs1045642 T allele carrier-rs2235048 C allele carrier group than in the rs1045642 non-T allele carrier-rs2235048 non-C allele carrier group. In addition, in the aripiprazole group, the T-C-T-A haplotype (rs1045642-rs2235048-rs1128503-rs2032582) was associated with decreased ANS activity. However, there were no significant associations between ANS activity and ABCB1 gene polymorphisms in the risperidone, olanzapine, and quetiapine groups. Multiple regression analysis revealed that sympathetic and total nervous activities were significantly associated with the ABCB1 rs1045642-rs2235048 genotype and the T-C-T-A haplotype (rs1045642-rs2235048-rs1128503-rs2032582).

CONCLUSION

We suggest that ABCB1 genetic polymorphisms affect aripiprazole-related ANS dysfunction but do not affect risperidone-, olanzapine-, or quetiapine-related ANS dysfunction.

Effect of ABCB1 C3435T Polymorphism on Pharmacokinetics of Antipsychotics and Antidepressants

P-glycoprotein, encoded by ABCB1, is an ATP-dependent drug efflux pump which exports substances outside the cell. Some studies described connections between C3435T polymorphism T allele and lower P-glycoprotein expression; therefore, homozygous T/T could show higher plasma levels. Our aim was to evaluate the effect of C3435T on pharmacokinetics of 4 antipsychotics (olanzapine, quetiapine, risperidone and aripiprazole) and 4 antidepressants (trazodone, sertraline, agomelatine and citalopram). The study included 473 healthy volunteers receiving a single oral dose of one of these drugs, genotyped by real-time PCR. Multivariate analysis was performed to adjust the effect of sex and genotype of the main cytochrome P450 enzymes. C3435T polymorphism had an effect on olanzapine pharmacokinetics, as T/T individuals showed lower clearance and volume of distribution. T/T individuals showed lower T_1/2 of 9-OH-risperidone, but this difference disappeared after multivariate correction. T/T homozygous individuals showed lower dehydro-aripiprazole and trazodone area under the concentration-time curve, along with lower half-life and higher clearance of trazodone. C/T genotype was associated to higher citalopram maximum concentration. C3435T had no effect on quetiapine, sertraline or agomelatine pharmacokinetics. C3435T can affect the elimination of some drugs in different ways. Regarding risperidone, trazodone and dehydro-aripiprazole, we observed enhanced elimination while it was reduced in olanzapine and citalopram. However, in quetiapine, aripiprazole, sertraline and agomelatine, no changes were detected. These results suggest that P-glycoprotein polymorphisms could affect CNS drugs disposition, but the genetic factor that alters its activity is still unknown. This fact leads to consider the analysis of ABCB1 haplotypes instead of individual variants.

ABCB1 and CYP2D6 polymorphisms and treatment response of psychotic patients in a naturalistic setting

OBJECTIVES

The aim of our study was to examine the association between ABCB1 polymorphisms G2677T/A (rs2032582) and C3435T (rs1045642) and common CYP2D6 variants, with the response to antipsychotic treatment of psychotic patients, in a naturalistic setting, in Greece.

METHODS

One hundred patients suffering from schizophrenia and other psychotic disorders were included in the study. Dosages were normalized to chlorpromazine equivalents. Response following 1 month of treatment was assessed as either a continuous variable, using the distribution of the corrected Positive and Negative Syndrome Scale percent change, or as a dichotomous variable defined as the number of patients scoring ≥30% from the corrected baseline Positive and Negative Syndrome Scale score. Genotyping was achieved with established polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

With response treated as a continuous variable, the homozygous recessive rs2032582 genotypes (TT) who were simultaneously carriers of a loss-of-function CYP2D6 allele (*4 or *5) responded significantly worse than the rest of the patients. Comparison of genotype frequencies revealed a statistically significant association of the above combination. No significant association between chlorpromazine equivalents and the tested genotypes was detected.

CONCLUSION

We have detected a possible interaction between ABCB1 and CYP2D6 in affecting response of psychotic patients to drug treatment, in a naturalistic setting.

The predictive value of ABCB1, ABCG2, CYP3A4/5 and CYP2D6 polymorphisms for risperidone and aripiprazole plasma concentrations and the occurrence of adverse drug reactions

We investigated in ninety Caucasian pediatric patients the impact of the main polymorphisms occurring in CYP3A, CYP2D6, ABCB1 and ABCG2 genes on second-generation antipsychotics plasma concentrations, and their association with the occurrence of adverse drug reactions. Patients with the CA/AA ABCG2 genotype had a statistically significant lower risperidone plasma concentration/dose ratio (Ct/ds) (P-value: 0.007) and an higher estimated marginal probability of developing metabolism and nutrition disorders as compared to the ABCG2 c.421 non-CA/AA genotypes (P-value: 0.008). Multivariate analysis revealed that the ABCG2 c.421 CA/AA genotype was found associated to a higher hazard (P-value: 0.004) of developing adverse drug reactions classified as metabolism and nutrition disorders. The ABCB1 2677TT/3435TT genotype had a statistically significant lower aripiprazole Ct/ds if compared with patients with others ABCB1 genotypes (P-value: 0.026). Information obtained on ABCB1 and ABCG2 gene variants may result useful to tailor treatments with these drugs in Caucasian pediatric patients.

Pharmacogenomics of autism spectrum disorder

Autism spectrum disorder (ASD) is characterized by persistent deficits in social communication and interactions as well as restricted, repetitive behaviors and interests. Pharmacologic interventions are often needed to manage irritability, aggressive behaviors and hyperactivity. Pharmacogenomic studies have investigated genetic associations with treatment response and side effects in an attempt to better understand drug mechanisms in hopes of optimizing the balance of symptom improvement versus side effects. The majority of pharmacogenomic studies to date have focused on antipsychotics, antidepressants and stimulants that are the most commonly utilized medication classes for ASD. This review is a comprehensive examination of the existing pharmacogenomic studies in ASD highlighting the current state of knowledge regarding genetic variation influencing pharmacokinetics and pharmacodynamics, and associated clinical outcomes.

Prediction of an Optimal Dose of Aripiprazole in the Treatment of Schizophrenia From Plasma Concentrations of Aripiprazole Plus Its Active Metabolite Dehydroaripiprazole at Week 1

BACKGROUND

It has been suggested that a plasma trough concentration of aripiprazole plus its active metabolite, dehydroaripiprazole of 225 ng/mL is a threshold for a good therapeutic response in the treatment of acutely exacerbated patients with schizophrenia. The present study investigated whether or not an optimal dose of aripiprazole could be predicted from these concentrations at week 1.

METHODS

The subjects were 26 inpatients with schizophrenia, who received aripiprazole once a day for 3 weeks. The daily doses were 12 mg for the first week and 24 mg for the next 2 weeks. No other drugs except biperiden and flunitrazepam were coadministered. Blood samples were taken at weeks 1 and 3 after the treatment. Plasma concentrations of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass-spectrometric detection.

RESULTS

There was a significant linear relationship between the plasma concentrations of aripiprazole plus dehydroaripiprazole at weeks 1 (x) and 3 (y) (P < 0.001). Regression equation was y = 2.580x + 34.86 (R = 0.698). Based on the equation, a nomogram to estimate an optimal dose of aripiprazole could be constructed.

CONCLUSIONS

The present study suggests that an optimal dose of aripiprazole for the treatment of patients with schizophrenia can be predicted from the plasma concentrations of the sum of the 2 compounds at week 1.

The Treatment of Adult Bipolar Disorder with Aripiprazole: A Systematic Review

Bipolar disorder is characterized by exacerbations of opposite mood polarity, ranging from manic to major depressive episodes. In the current nosological system of the Diagnostic and Statistical Manual – 5^th edition (DSM-5), it is conceptualized as a spectrum disorder consisting of bipolar disorder type I, bipolar disorder type II, cyclothymic disorder, and bipolar disorder not otherwise specified. Treatment of all phases of this disorder is primarily with mood stabilizers, but many patients either show resistance to the conventional mood stabilizing medications or are intolerant to their side-effects. In this setting, second-generation antipsychotics have gained prominence as many bipolar subjects who are otherwise treatment refractory show response to these agents. Aripiprazole is a novel antipsychotic initially approved for the treatment of schizophrenia but soon found to be effective in bipolar disorder. This drug is well studied, as randomized controlled trials have been conducted in various phases of bipolar disorders. Aripiprazole exhibits the pharmacodynamic properties of partial agonism, functional selectivity, and serotonin-dopamine activity modulation – the new exemplars in the treatment of major psychiatric disorders. It is the first among a new series of psychotropic medications, which now also include brexpiprazole and cariprazine. The current review summarizes the data from controlled trials regarding the efficacy and safety of aripiprazole in adult bipolar patients. On the basis of this evidence, aripiprazole is found to be efficacious in the treatment and prophylaxis of manic and mixed episodes but has no effectiveness in acute and recurrent bipolar depression.