Prolactin release in children treated with risperidone: impact and role of CYP2D6 metabolism

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 ≤ 18 years old with at least 8 weeks 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.

Influence of CYP2C19 and CYP2D6 on side effects of aripiprazole and risperidone: A systematic review

Variability in hepatic cytochrome P450 (CYP) enzymes such as 2C19 and 2D6 may influence side-effect and efficacy outcomes for antipsychotics. Aripiprazole and risperidone are two commonly prescribed antipsychotics, metabolized primarily through CYP2D6. Here, we aimed to provide an overview of the effect of CYP2C19 and CYP2D6 on side-effects of aripiprazole and risperidone, and expand on existing literature by critically examining methodological issues associated with pharmacogenetic studies. A PRISMA compliant search of six electronic databases (Pubmed, PsychInfo, Embase, Central, Web of Science, and Google Scholar) identified pharmacogenetic studies on aripiprazole and risperidone. 2007 publications were first identified, of which 34 were included. Quality of literature was estimated using Newcastle-Ottowa Quality Assessment Scale (NOS) and revised Cochrane Risk of Bias tool. The average NOS score was 5.8 (range: 3-8) for risperidone literature and 5 for aripiprazole (range: 4-6). All RCTs on aripiprazole were rated as high risk of bias, and four out of six for risperidone literature. Study populations ranged from healthy volunteers to inpatient individuals in psychiatric units and included adult and pediatric samples. All n = 34 studies examined CYP2D6. Only one study genotyped for CYP2C19 and found a positive association with neurological side-effects of risperidone. Most studies did not report any relationship between CYP2D6 and any side-effect outcome. Heterogeneity between and within studies limited the ability to synthesize data and draw definitive conclusions. Studies lacked statistical power due to small sample size, selective genotyping methods, and study design. Large-scale randomized trials with multiple measurements, providing robust evidence on this topic, are suggested.

Exploratory focused pharmacogenetic testing reveals novel markers associated with risperidone pharmacokinetics in Saudi children with autism

Background: Autism spectrum disorders (ASDs) encompass a broad range of phenotypes characterized by diverse neurological alterations. Genomic studies have revealed considerable overlap between the molecular mechanisms implicated in the etiology of ASD and genes involved in the pharmacokinetic (PK) and pharmacodynamic (PD) pathways of antipsychotic drugs employed in ASD management. Given the conflicting data originating from candidate PK or PD gene association studies in diverse ethnogeographic ASD populations, dosage individualization based on "actionable" pharmacogenetic (PGx) markers has limited application in clinical practice. Additionally, off-label use of different antipsychotics is an ongoing practice, which is justified given the shortage of approved cures, despite the lack of satisfactory evidence for its safety according to precision medicine. This exploratory study aimed to identify PGx markers predictive of risperidone (RIS) exposure in autistic Saudi children. Methods: This prospective cohort study enrolled 89 Saudi children with ASD treated with RIS-based antipsychotic therapy. Plasma levels of RIS and 9-OH-RIS were measured using a liquid chromatography-tandem mass spectrometry system. To enable focused exploratory testing, genotyping was performed with the Axiom PharmacoFocus Array, which included a collection of probe sets targeting PK/PD genes. A total of 720 PGx markers were included in the association analysis. Results: A total of 27 PGx variants were found to have a prominent impact on various RIS PK parameters; most were not located within the genes involved in the classical RIS PK pathway. Specifically, 8 markers in 7 genes were identified as the PGx markers with the strongest impact on RIS levels (p < 0.01). Four PGx variants in 3 genes were strongly associated with 9-OH-RIS levels, while 5 markers in 5 different genes explained the interindividual variability in the total active moiety. Notably, 6 CYP2D6 variants exhibited strong linkage disequilibrium; however, they significantly influenced only the metabolic ratio and had no considerable effects on the individual estimates of RIS, 9-OH-RIS, or the total active moiety. After correction for multiple testing, rs78998153 in UGT2B17 (which is highly expressed in the brain) remained the most significant PGx marker positively adjusting the metabolic ratio. For the first time, certain human leukocyte antigen (HLA) markers were found to enhance various RIS exposure parameters, which reinforces the gut-brain axis theory of ASD etiology and its suggested inflammatory impacts on drug bioavailability through modulation of the brain, gastrointestinal tract and/or hepatic expression of metabolizing enzymes and transporters. Conclusion: Our hypothesis-generating approach identified a broad spectrum of PGx markers that interactively influence RIS exposure in ASD children, which indicated the need for further validation in population PK modeling studies to define polygenic scores for antipsychotic efficacy and safety, which could facilitate personalized therapeutic decision-making in this complex neurodevelopmental condition.

Influence of CYP2D6 Metabolizer Status on Risperidone and Paliperidone Tolerability in Children and Adolescents

Background: Risperidone and, to a lesser extent, paliperidone are metabolized by CYP2D6; however, there are limited data related to variation in CYP2D6 phenotypes and the tolerability of these medications in children and adolescents. Furthermore, the impact of CYP2D6 on the association of risperidone and paliperidone with hyperprolactinemia in youth is not well understood. Methods: A retrospective chart review was performed in psychiatrically hospitalized children and adolescents prescribed risperidone (n = 263, age = 3-18 years, mean age = 13 ± 3 years, 49% female) or paliperidone (n = 124, age = 5-18 years, mean age = 15 ± 2 years, 44% female) who had CYP2D6 genotyping performed as part of routine care. CYP2D6 phenotypes were determined based on Clinical Pharmacogenetics Implementation Consortium guidelines and CYP2D6 inhibitors causing phenoconversion. Adverse effects were obtained from a review of the electronic health record, and patients were selected, in part, to enrich non-normal metabolizers. Results: Among risperidone-treated patients, 45% experienced an adverse effect, whereas 36% of paliperidone-treated patients experienced adverse effects. Discontinuation of risperidone due to lack of efficacy was more frequent in the CYP2D6 normal metabolizers and ultrarapid metabolizers compared with intermediate metabolizers (IMs) and phenoconverted poor metabolizers (pPMs) (54.5% vs. 32.7%, p < 0.001). Discontinuation due to weight gain was more common among risperidone- than paliperidone-treated patients (17% vs. 7%, p = 0.011). Among those taking paliperidone, CYP2D6 was associated with discontinuation due to side effects (p = 0.008), and youth with slower CYP2D6 metabolism (i.e., pPMs and IMs) were more likely to discontinue. Hyperprolactinemia was found in 10% of paliperidone-treated patients and 5% of risperidone-treated patients, and slower CYP2D6 metabolizers required higher risperidone doses to cause hyperprolactinemia (p = 0.011). Conclusions: CYP2D6 phenotype is associated with discontinuation of risperidone due to lack of efficacy and the dose of risperidone that induced hyperprolactinemia, as well as discontinuation of paliperidone due to adverse effects. Future studies should evaluate exposure-response and toxicity relationships in risperidone- and paliperidone-treated youth.

Clinical pharmacokinetics of antipsychotics in pediatric populations: a scoping review focusing on dosing regimen

INTRODUCTION

Achieving optimal clinical responses and minimizing side effects through precision dosing of antipsychotics in children and adolescents with psychiatric disorders remains a challenge. Identifying patient characteristics (covariates) that affect pharmacokinetics can inform more effective dosing strategies and ultimately improve patient outcomes. This review aims to provide greater insight into the impact of covariates on the clinical pharmacokinetics of antipsychotics in pediatric populations.

AREAS COVERED

A comprehensive literature search was conducted, and the main findings regarding the effects of the covariates on the pharmacokinetics of antipsychotics in children and adolescents are presented.

EXPERT OPINION

Our study highlights significant covariates, including age, sex, weight, CYP2D6 phenotype, co-medication, and smoking habits, which affect the pharmacokinetics of antipsychotics. However, the findings were generally limited by the small sample sizes of naturalistic, open-label, observational studies, and the homogeneous subgroups. Dosing based on weight and preemptive genotyping could prove beneficial for optimizing the dosing regimen in pediatric populations. Future research is needed to refine dosing recommendations and establish therapeutic reference ranges critical for precision dosing and Therapeutic Drug Monitoring (TDM). The integration of individual patient characteristics with TDM can further optimize the efficacy and safety of antipsychotics for each patient.

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.

Therapeutic drug monitoring in children and adolescents with schizophrenia and other psychotic disorders using risperidone

Risperidone is commonly used to treat different psychiatric disorders worldwide. Knowledge on dose–concentration relationships of risperidone treatment in children and adolescents with schizophrenia or other psychotic disorders is, however, scarce and no age-specific therapeutic ranges have been established yet. Multicenter data of a therapeutic drug monitoring service were analyzed to evaluate the relationship between risperidone dose and serum concentration of the active moiety (risperidone (RIS) plus its main metabolite 9-hydroxyrisperidone (9-OH-RIS)) in children and adolescents with psychotic disorders. Patient characteristics, doses, serum concentrations and therapeutic outcomes were assessed by standardized measures. The study also aimed to evaluate whether the therapeutic reference range for adults (20–60 ng/ml) is applicable for minors. In the 64 patients (aged 11–18 years) included, a positive correlation between daily dose and the active moiety (RIS_am) concentration was found (r_s = 0.49, p = 0.001) with variation in dose explaining 24% (r_s² = 0.240) of the variability in serum concentrations. While the RIS_am concentration showed no difference, RIS as well 9-OH-RIS concentrations and the parent to metabolite ratio varied significantly in patients with co-medication of a CYP2D6 inhibitor. Patients with extrapyramidal symptoms (EPS) had on average higher RISam concentrations than patients without (p = 0.05). Considering EPS, the upper threshold of the therapeutic range of RIS_am was determined to be 33 ng/ml. A rough estimation method also indicated a possibly decreased lower limit of the preliminary therapeutic range in minors compared to adults. These preliminary data may contribute to the definition of a therapeutic window in children and adolescents with schizophrenic disorders treated with risperidone. TDM is recommended in this vulnerable population to prevent concentration-related adverse drug reactions.

Pharmacogenomic Studies in Intellectual Disabilities and Autism Spectrum Disorder: A Systematic Review

BACKGROUND

Individuals with intellectual disability (ID) and autism spectrum disorder (ASD) often receive psychotropic medications such as antipsychotics and antidepressants to treat aberrant behaviors and mood symptoms, frequently resulting in polypharmacy and drug-related adverse effects. Pharmacogenomic (PGx) studies with ASD and/or ID (ASD/ID) have been scarce despite the promise of optimizing treatment outcomes. We reviewed the literature on PGx studies with antipsychotics and antidepressants (e.g., treatment response and adverse effects) in ASD/ID.

METHODS

We performed a systematic review using MEDLINE, Embase, and PsycINFO, including peer-reviewed original articles in English referring to PGx in the treatment of ASD/ID in any age groups (e.g., treatment response and adverse effects).

RESULTS

A total of 28 PGx studies using mostly candidate gene approaches were identified across age groups. Notably, only 3 studies included adults with ASD/ID while the other 25 studies focused specifically on children/adolescents with ASD/ID. Twelve studies primarily investigated treatment response, of which 5 and 6 studies included patients treated with antipsychotics and antidepressants, respectively. Most interesting results for response were reported for 2 sets of candidate gene studies, namely: (1) The DRD3 Ser9Gly (rs6280) polymorphism was examined in patients treated with risperidone in 3 studies, 2 of which reported an association with risperidone treatment response and (2) the SLC6A4 5-HTTLPR polymorphism and treatment response to antidepressants which was investigated in 4 studies, 3 of which reported significant associations. In regard to side effects, 9 of 15 studies focused on hyperprolactinemia in patients treated with risperidone. Among them, 7 and 5 studies examined the impact of CYP2D6 and DRD2 Taq1A polymorphisms, respectively, yielding mostly negative study findings.

CONCLUSIONS

There is limited data available on PGx in individuals with ASD/ID and in particular in adults. Given the potential for PGx testing in improving treatment outcomes, additional PGx studies for psychotropic treatment in ASD/ID across age groups are warranted.

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.

CYP2D6 and Antipsychotic Treatment Outcomes in Children and Youth: A Systematic Review

Objective: To systematically review the impact of CYP2D6 genetic variation on antipsychotic pharmacokinetics, efficacy, and adverse drug reactions among children and youth. Method: The published literature was systematically searched in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations and critically evaluated using standardized tools and consensus criteria. Results: A total of 20 eligible studies comprising 1078 children and youth were evaluated. The included studies were of fair to moderate quality and included mostly males, individuals of European ancestry, and those treated with risperidone. CYP2D6 poor metabolizers (PMs) were consistently shown to have increased concentrations of risperidone relative to normal metabolizers (NMs). PMs were also consistently shown to have a greater propensity to experience antipsychotic (primarily risperidone) associated adverse drug reactions relative to NMs. However, robust evidence for an association between CYP2D6 and efficacy was less apparent. Conclusion and Clinical Significance: The current knowledge base suggests that CYP2D6 genetic variation has an appreciable impact on antipsychotic pharmacokinetics and the propensity for adverse drug reactions, particularly among children receiving risperidone treatment. However, several limitations with the current literature (e.g., sample sizes, study design, sample heterogeneity) should be addressed in future studies. Assuming that future studies support the link between CYP2D6 genetic variation and antipsychotic outcomes, we would anticipate an increase in the implementation of CYP2D6-guided antipsychotic drug selection and dose optimization in child and adolescent psychiatric services.

Pharmacogenetic Testing of Cytochrome P450 Drug Metabolizing Enzymes in a Case Series of Patients with Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is associated with co-morbid psychiatric symptoms (disruptive behavior, anxiety, mood disorders, and psychosis) often requiring psychotropic medications. In this clinical case series of 35 patients with PWS, pharmacogenetic testing was obtained to determine allele frequencies predicting variations in activity of cytochrome (CYP) P450 drug metabolizing enzymes 2D6, 2B6, 2C19, 2C9, 3A4, and 1A2. Results were deidentified, collated, and analyzed by PWS genetic subtype: 14 deletion (DEL), 16 maternal uniparental disomy (UPD) and 5 DNA-methylation positive unspecified molecular subtype (PWS Unspec). Literature review informed comparative population frequencies of CYP polymorphisms, phenotypes, and substrate specificity. Among the total PWS cohort, extensive metabolizer (EM) activity prevailed across all cytochromes except CYP1A2, which showed greater ultra-rapid metabolizer (UM) status (p < 0.05), especially among UPD. Among PWS genetic subtypes, there were statistically significant differences in metabolizing status for cytochromes 2D6, 2C19, 2C9, 3A4 and 1A2 acting on substrates such as fluoxetine, risperidone, sertraline, modafinil, aripiprazole, citalopram, and escitalopram. Gonadal steroid therapy may further impact metabolism of 2C19, 2C9, 3A4 and 1A2 substrates. The status of growth hormone treatment may affect CYP3A4 activity with gender specificity. Pharmacogenetic testing together with PWS genetic subtyping may inform psychotropic medication dosing parameters and risk for adverse events.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Risperidone plasma concentrations are associated with side effects and effectiveness in children and adolescents with autism spectrum disorder

AIM

Risperidone is the most commonly prescribed antipsychotic drug to children and adolescents worldwide, but it is associated with serious side effects, including weight gain. This study assessed the relationship of risperidone and 9-hydroxyrisperidone trough concentrations, maximum concentrations and 24-hour area under the curves (AUCs) with body mass index (BMI) z-scores in children and adolescents with autism spectrum disorder (ASD) and behavioural problems. Secondary outcomes were metabolic, endocrine, extrapyramidal and cardiac side effects and effectiveness.

METHODS

Forty-two children and adolescents (32 males) aged 6-18 years were included in a 24-week prospective observational trial. Drug plasma concentrations, side effects and effectiveness were measured at several time points during follow-up. Relevant pharmacokinetic covariates, including medication adherence and CYP2D6, CYP3A4, CYP3A5 and P-glycoprotein (ABCB1) genotypes, were measured. Nonlinear mixed-effects modelling (NONMEM®) was used for a population pharmacokinetic analysis with 205 risperidone and 205 9-hydroxyrisperidone concentrations. Subsequently, model-based trough concentrations, maximum concentrations and 24-hour AUCs were analysed to predict outcomes using generalized and linear mixed-effects models.

RESULTS

A risperidone two-compartment model combined with a 9-hydroxyrisperidone one-compartment model best described the measured concentrations. Of all the pharmacokinetic parameters, higher risperidone sum trough concentrations best predicted higher BMI z-scores during follow-up (P < .001). Higher sum trough concentrations also predicted more sedation (P < .05), higher prolactin levels (P < .001) and more effectiveness measured with Aberrant Behavior Checklist irritability score (P < .01).

CONCLUSION

Our results indicate a therapeutic window exists, which suggests that therapeutic drug monitoring of risperidone might increase safety and effectiveness in children and adolescents with ASD and behavioural problems.

CYP2D6 Genetic Polymorphisms and Risperidone Pharmacokinetics: A Systematic Review and Meta-analysis

BACKGROUND

Risperidone is a second-generation antipsychotic drug metabolized to an active metabolite, 9-hydroxyrisperidone, primarily by cytochrome P450 (CYP) 2D6 and to a lesser extent by CYP3A4. The extent to which drug metabolism genetics impacts risperidone and 9-hydroxyrisperidone exposure has not been clarified.

OBJECTIVE

A systematic review and meta-analysis evaluated the impact of genetically defined CYP2D6 function on risperidone pharmacokinetics applying a standardized genotype-phenotype translation system.

METHODS

A comprehensive electronic database search identified studies reporting relationships between genetically determined CYP2D6 metabolism and risperidone pharmacokinetic properties. The exposure of risperidone or active moiety (risperidone + 9-hydroxyrisperidone) was measured by dose-adjusted steady-state serum or plasma concentration or area under the concentration-time curve as primary outcomes. Subjects were assigned to CYP2D6 poor metabolizer, intermediate metabolizer, normal metabolizer, or ultrarapid metabolizer groups using a standardized genotype-phenotype translation method. Effect sizes between groups were pooled and stratified by single or multiple dosing regimens.

RESULTS

A total of 15 studies involving 2125 adult subjects were included in the meta-analysis. Following multiple-dose oral administration, compared with CYP2D6 normal metabolizers, the risperidone dose-adjusted steady-state serum/plasma concentration was 2.35-fold higher in intermediate metabolizers (95% confidence interval [CI] 1.77-3.13, p<0.0001) and 6.20-fold higher in poor metabolizers (95% CI 5.05-7.62, p<0.0001); the active moiety dose-adjusted steady-state concentration was 1.18-fold higher in intermediate metabolizers (95% CI 1.11-1.25, p<0.0001) and 1.44-fold higher in poor metabolizers (95% CI 1.23-1.69, p<0.0001). Higher area under the concentration-time curve of risperidone and active moiety was also found in single-dose studies.

CONCLUSION

Genetically defined impaired CYP2D6 activity is associated with increased exposure of both risperidone and risperidone + 9-hydroxyrisperidone in adults receiving oral formulations. Additional studies are needed to quantify the clinical impact of these relationships.

Psychotropic drug concentrations and clinical outcomes in children and adolescents: a systematic review

INTRODUCTION

The use of psychotropic drugs in children and adolescents is widespread but associated with suboptimal treatment effects. Therapeutic drug monitoring (TDM) can improve safety of psychotropic drugs in children and adolescents but is not routinely performed. A major reason is that the relationship between drug concentrations and effects is not well known.

AREAS COVERED

This systematic review evaluated studies assessing the relationship between psychotropic drug concentrations and clinical outcomes in children and adolescents, including antipsychotics, psychostimulants, alpha-agonists, antidepressants, and mood-stabilizers. PRISMA guidelines were used and a quality assessment of the retrieved studies was performed. Sixty-seven eligible studies involving 24 psychotropic drugs were identified from 9,298 records. The findings were generally heterogeneous and the majority of all retrieved studies were not of sufficient quality. For 11 psychotropic drugs, a relationship between drug concentrations and side-effects and/or effectiveness was evidenced in reasonably reported and executed studies, but these findings were barely replicated.

EXPERT OPINION

In order to better support routine TDM in child- and adolescent psychiatry, future work must improve in aspects of study design, execution and reporting to demonstrate drug concentration-effect relationships. The quality criteria proposed in this work can guide future TDM research. Systematic review protocol and registration PROSPERO CRD42018084159.

The effect of CYP2D6 variation on antipsychotic-induced hyperprolactinaemia: a systematic review and meta-analysis

Hyperprolactinemia is a known adverse drug reaction to antipsychotic treatment. Antipsychotic blood levels are influenced by cytochrome P450 enzymes, primarily CYP2D6. Variation in CYP450 genes may affect the risk of antipsychotic-induced hyperprolactinemia. We undertook a systematic review and meta-analysis to assess whether CYP2D6 functional genetic variants are associated with antipsychotic-induced hyperprolactinemia. The systematic review identified 16 relevant papers, seven of which were suitable for the meta-analysis (n = 303 participants including 134 extreme metabolisers). Participants were classified into four phenotype groups as poor, intermediate, extensive, and ultra-rapid metabolisers. A random effects meta-analysis was used and Cohen's d calculated as the effect size for each primary study. We found no significant differences in prolactin levels between CYP2D6 metabolic groups. Current evidence does not support using CYP2D6 genotyping to reduce risk of antipsychotic-induced hyperprolactinemia. However, statistical power is limited. Future studies with larger samples and including a range of prolactin-elevating drugs are needed.

Safety and Tolerability of Antipsychotic Medication in Individuals with Autism Spectrum Disorder: A Systematic Review and Meta-Analysis

BACKGROUND

Antipsychotic medication is a commonly prescribed drug class in individuals with autism spectrum disorder (ASD). However, the safety of these agents has not been fully assessed.

OBJECTIVE

Our objective was to investigate the safety and tolerability profile of antipsychotics in individuals with ASD.

METHODS

The Cochrane Library, MEDLINE, Embase and PsycINFO databases were searched up to January 2018. We included studies that reported adverse events (AEs) in participants with ASD taking first- or second-generation antipsychotic medication. The studies included in the analysis were randomized controlled trials (RCTs) and observational studies that were comparative or noncomparative and published as full text in the English language. The primary outcome of this review was AEs of any severity reported with antipsychotic use at any dose. Meta-analysis was performed on studies with child and adolescent participants to estimate the pooled prevalence of the overall AEs and the relative risk (RR) of AEs associated with antipsychotic use using a random-effects model. The Cochrane Collaboration tool and the modified Newcastle-Ottawa Scale (NOS) were used to assess the risk of bias of the included RCTs and observational studies, respectively.

RESULTS

In total, 54 citations fulfilled the inclusion criteria, of which 40 were RCTs and 14 were observational studies; eight RCTs were included in the meta-analysis to estimate the RR of AEs associated with antipsychotic use and seven observational studies were included to estimate the pooled prevalence of AEs. The RR of AEs with antipsychotic treatment was 22% higher than with placebo (RR 1.22; 95% confidence interval [CI] 1.11-1.34; I² = 30.6%; p = 0.184). The estimated pooled prevalence of AEs was 50.5% (95% CI 33-67). The most commonly reported AEs were increased appetite and weight gain, which were associated with discontinuation in many participants.

CONCLUSION

Antipsychotic-related AEs were common among patients with ASD. Further studies to investigate the implications of antipsychotic-related AEs on health and medication adherence are warranted. PROSPERO registration number: (CRD42018083632).

Association of dopamine D2 receptor gene polymorphisms with prolactin levels related to risperidone treatment: A systematic review and meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Dopamine D₂ receptor (DRD2) polymorphisms are inconsistently associated with elevated prolactin levels related to risperidone treatment. The aim of this systematic review and meta-analysis was to investigate whether DRD2 polymorphisms could modulate prolactin levels in patients treated with risperidone.

METHODS

Three electronic databases (PubMed, EMBASE and the Cochrane Library) were searched for studies investigating the effect of DRD2 polymorphisms on prolactin levels in patients treated with risperidone until May 2018. Summary standard mean differences (SMDs) and 95% confidence intervals (CIs) were calculated with Hedges' g tests for effect estimates using random effects models. The heterogeneity, sensitivity, univariable meta-regression, subgroup analyses and publication biases were calculated.

RESULTS AND DISCUSSION

After initially identifying 886 studies, 772 patients from eight studies were included. Summary SMDs indicated that compared with A1 non-carriers, Taq1A A1 carriers did not have different risperidone-related prolactin levels (SMD: 0.13; 95% CI: -0.18 to 0.43; P = 0.423) among patients with schizophrenia (SCZ; SMD: 0.07; 95% CI: -0.14 to 0.29; P = 0.505) or among those without SCZ (SMD: 0.16; 95% CI: -0.39 to 0.71; P = 0.562). There was no significant difference between Del carriers and Del non-carriers with regard to risperidone-related prolactin levels (SMD: -0.00; 95% CI: -0.59 to 0.58; P = 0.996). In an Asian subgroup analysis, we also noted that compared with Taq1A A1A2 carriers, Taq1A A1A1 carriers had lower prolactin levels (SMD: -0.34; 95% CI: -0.66 to -0.02; P = 0.040). However, there was no significant difference in prolactin levels between A1A1 carriers and A2A2 carriers (SMD: -0.27; 95% CI: -0.60 to 0.05; P = 0.098), or between A2 carriers and A2 non-carriers (SMD: 0.29; 95% CI: -0.01 to 0.59; P = 0.059). Based on univariable meta-regression analyses, the effects of publication year, study design, ethnicity, comparison groups and study quality could bias the identified association of DRD2 Taq1A with risperidone-related prolactin levels.

WHAT IS NEW AND CONCLUSION

The findings of this study suggest that there is no significant difference between Taq1A A1 carriers and non-A1 carriers with regard to risperidone-related prolactin levels. As there were few A1 homozygotes, large prospective studies with robust designs are still needed to investigate whether A1A1 could affect risperidone-related prolactin levels in the Asian population.

CYP2D6 genotype and adverse events to risperidone in children and adolescents

BACKGROUND

There are few and conflicting data on the role of cytochrome P450 2D6 (CYP2D6) polymorphisms in relation to risperidone adverse events (AEs) in children. This study assessed the association between CYP2D6 metabolizer status and risk for risperidone AEs in children.

METHODS

Children ≤18 years with at least 4 weeks of risperidone exposure were identified using BioVU, a de-identified DNA biobank linked to electronic health record data. The primary outcome of this study was AEs. After DNA sequencing, individuals were classified as CYP2D6 poor, intermediate, normal, or ultrarapid CYP2D6 metabolizers.

RESULTS

For analysis, the 257 individuals were grouped as poor/intermediate metabolizers (n = 33, 13%) and normal/ultrarapid metabolizers (n = 224, 87%). AEs were more common in poor/intermediate vs. normal/ultrarapid metabolizers (15/33, 46% vs. 61/224, 27%, P = 0.04). In multivariate analysis adjusting for age, sex, race, and initial dose, poor/intermediate metabolizers had increased AE risk (adjusted odds ratio 2.4, 95% confidence interval 1.1-5.1, P = 0.03).

CONCLUSION

Children with CYP2D6 poor or intermediate metabolizer phenotypes are at greater risk for risperidone AEs. Pre-prescription genotyping could identify this high-risk subset for an alternate therapy, risperidone dose reduction, and/or increased monitoring for AEs.

A systematic review of the effects of CYP2D6 phenotypes on risperidone treatment in children and adolescents

The second generation antipsychotic drug risperidone is widely used in the field of child and adolescent psychiatry to treat conditions associated with disruptive behavior, aggression and irritability, such as autism spectrum disorders. While risperidone can provide symptomatic relief for many patients, there is considerable individual variability in the therapeutic response and side-effect profile of the medication. One well established biological factor that contributes to these individual differences is genetic variation in the cytochrome P450 enzyme 2D6. The 2D6 enzyme metabolizes risperidone and therefore affects drug levels and dosing. In the present review, we summarize the current literature on 2D6 variants and their effects on risperidone responses, specifically in children and adolescents. Relevant articles were identified through systematic review, and after irrelevant articles were discarded, ten studies were included in the review. Most prospective studies were well controlled, but often did not have a large enough sample size to make robust statements about rarer variants, including those categorized as ultra-rapid and poor metabolizers. Individual studies demonstrated a role for different genetic variants in risperidone drug efficacy, pharmacokinetics, hyperprolactinemia, weight gain, extrapyramidal symptoms and drug-drug interactions. Where studies overlapped in measurements, there was typically a consensus between results. These findings indicate that the value of 2D6 genotyping in the youth population treated with risperidone requires further study, in particular with the less common variants.

Evaluation of the Role of ABCB1gene Polymorphic Variants on Psychiatric Disorders Predisposition in Macedonian Population

The psychiatric and other CNS disorders are characterized with unregulated neuro-inflammatory processes and chronic microglia cell activation resulting with detrimental effect. ABCB1gene polymorphismsC1236T, G2677T/Aand C3435T are associated with P-glycoprotein expression and function andare linked with predisposition to psychiatric disorders such as schizophrenia and bipolar disorders. The relationship between mood disorders and glucocorticoids has been confirmed and ABCB1 SNPs influence the glucocorticoids access to the brain. The aim of the study is evaluation of the influence of the three most common ABCB1SNPs on predisposition to psychiatric disorders in Macedonian population. In the study 107 unrelated healthy Macedonians of both sexes were enrolled as a control group and patient population of 54 patients (22 to 65 years old) diagnosed with schizophrenia or bipolar disorder. ABCB1 for three polymorphisms were analyzed by Real-Time PCR in both groups. The results have confirmed the role of the ABCB1 gene in predisposition to psychiatric disorders and increased risk of developing bipolar disorder in carriers of the heterozygotes and mutant homozygotes for polymorphic variations in 1236 and 2677 in comparison to the normal genotype carriers. Three-fold higher risk was estimated for psychiatric illness in women that are 1236 and 2677 heterozygous carrier (heterozygous and mutant homozygous) compared to healthy control (men and women) population and four-fold higher risk in comparison only to healthy women population. Mutant allele carriers for 1236 and 2677 polymorphisms that are 35 years and below in patients population have almost three-fold higher risk for development of psychiatric illness.

Clinical Pharmacogenetics of Cytochrome P450-Associated Drugs in Children

Cytochrome P450 (CYP) enzymes are commonly involved in drug metabolism, and genetic variation in the genes encoding CYPs are associated with variable drug response. While genotype-guided therapy has been clinically implemented in adults, these associations are less well established for pediatric patients. In order to understand the frequency of pediatric exposures to drugs with known CYP interactions, we compiled all actionable drug-CYP interactions with a high level of evidence using Clinical Pharmacogenomic Implementation Consortium (CPIC) data and surveyed 10 years of electronic health records (EHR) data for the number of children exposed to CYP-associated drugs. Subsequently, we performed a focused literature review for drugs commonly used in pediatrics, defined as more than 5000 pediatric patients exposed in the decade-long EHR cohort. There were 48 drug-CYP interactions with a high level of evidence in the CPIC database. Of those, only 10 drugs were commonly used in children (ondansetron, oxycodone, codeine, omeprazole, lansoprazole, sertraline, amitriptyline, citalopram, escitalopram, and risperidone). For these drugs, reports of the drug-CYP interaction in cohorts including children were sparse. There are adequate data for implementation of genotype-guided therapy for children for three of the 10 commonly used drugs (codeine, omeprazole and lansoprazole). For the majority of commonly used drugs with known CYP interactions, more data are required to support pharmacogenomic implementation in children.

Pharmacogenetics of Risperidone: A Systematic Review of the Clinical Effects of CYP2D6 Polymorphisms

OBJECTIVE

To summarize and evaluate the pharmacogenetic literature pertaining to the effects of CYP2D6 polymorphism on clinical outcomes of risperidone therapy.

DATA SOURCES

A systematic literature search was performed using the search terms risperidone, pharmacogenetics, cytochrome P-450 enzyme system, cytochrome P-450 CYP2D6, and polymorphism (genetic) in MEDLINE (1946-October 2012), EMBASE (1980-October 2012), PubMed (1947-October 2012), International Pharmaceutical Abstracts (1970-October 2012), and Google Scholar.

STUDY SELECTION AND DATA EXTRACTION

Identified articles were included if they measured the association between CYP2D6 genetic polymorphisms and clinical outcomes in at least 2 patients taking risperidone. The data elements extracted from these articles consisted of study design, number of subjects, indication for risperidone therapy, CYP2D6 phenotype status, mean daily dose of risperidone, and effects on clinical outcomes.

DATA SYNTHESIS

The identified citations consisted of 10 prospective nonrandomized, uncontrolled cohort studies, 1 retrospective cohort study, 1 prospective case-control study, and 1 retrospective case series. Studies were of variable quality and none provided high-quality evidence; they included heterogeneous patient populations with varying clinical diagnoses and drug therapy regimens. Most studies reported nonsignificant trends but were limited by power to detect statistical significance and short trial duration. However, increased risk of adverse effects (including QT interval prolongation) was observed in patients with inactive alleles.

CONCLUSIONS

While there were trends toward increased adverse effects in poor metabolizers, most outcomes were not significant. As such, routine genotyping should not be used for screening. Future usefulness cannot be ruled out, as many studies had significant limitations that preclude determination of clinical relevance. Adequately powered clinical and epidemiologic studies are warranted to clarify the role of CYP2D6 genotyping in practice.

CYP2D6 polymorphisms and their influence on risperidone treatment

Cytochrome P450 enzyme especially CYP2D6 plays a major role in biotransformation. The interindividual variations of treatment response and toxicity are influenced by the polymorphisms of this enzyme. This review emphasizes the effect of CYP2D6 polymorphisms in risperidone treatment in terms of basic knowledge, pharmacogenetics, effectiveness, adverse events, and clinical practice. Although the previous studies showed different results, the effective responses in risperidone treatment depend on the CYP2D6 polymorphisms. Several studies suggested that CYP2D6 polymorphisms were associated with plasma concentration of risperidone, 9-hydroxyrisperidone, and active moiety but did not impact on clinical outcomes. In addition, CYP2D6 poor metabolizer showed more serious adverse events such as weight gain and prolactin than other predicted phenotype groups. The knowledge of pharmacogenomics of CYP2D6 in risperidone treatment is increasing, and it can be used for the development of personalized medication in term of genetic-based dose recommendation. Moreover, the effects of many factors in risperidone treatment are still being investigated. Both the CYP2D6 genotyping and therapeutic drug monitoring are the important steps to complement the genetic-based risperidone treatment.

Hyperprolactinemia in Children and Adolescents with Use of Risperidone: Clinical and Molecular Genetics Aspects

OBJECTIVE

In children and adolescents treated with risperidone, hyperprolactinemia is a frequent complication that may have clinical repercussions. Several genes have been associated with this occurrence. The aim of this study was to evaluate the frequency of hyperprolactinemia in children and adolescents treated with risperidone, and its associations with clinical and pharmacological data and certain polymorphisms of the following genes: Dopamine receptor D2 (DRD2), 5-hydroxytryptamine (serotonin) receptor 2C (HTR2C), cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6), leptin (LEP), leptin receptor (LEPR), melanocortin 4 receptor (MC4R), and scavenger receptor class B, member 2 (SCARB2).

METHODS

The study included patients using risperidone (8-20 years old) and healthy subjects not exposed to the medication. Psychopathological symptoms, doses, and duration of treatment with risperidone, sex, skin color, body mass index (BMI), use of other psychotropic drugs, and polymorphisms of DRD2, HTR2C, CYP2D6, LEP, LEPR, MC4R, and SCARB2 genes were evaluated.

RESULTS

There were 120 patients and 197 individuals not exposed to risperidone who were evaluated. Among patients, hyperprolactinemia was found in 79 (65.8%) cases, with no differences regarding sex, skin color, or being in monotherapy with risperidone (26.7% of total patients) or not. The level of prolactin was not correlated, either in case or control groups, with chronological age, bone age, prescribed dose of risperidone, weight-adjusted dose of risperidone, or BMI (p > 0.05), but was negatively correlated with the treatment duration (r = -0.352, p = 0.001 among cases; and r = -0.324, p = 0.039 among controls). There were significant differences in use of risperidone between patients and healthy subjects without the medication in the frequency of the polymorphisms of the DRD2, HTR2C, and LEP genes. Considering both sexes together and also specifically among females, the occurrence of hyperprolactinemia was higher in the presence of the C allele of the rs6318 single nucleotide polymorphisms (SNP) of the HTR2C gene.

CONCLUSIONS

This group of children and adolescents with or without isolated use of risperidone presented with a high frequency of hyperprolactinemia, although asymptomatic, and associated, when considering only females or both sexes together, with being a carrier of the C allele of the rs6318 SNP of the HTR2C gene.

Prolactin variations during risperidone therapy in a sample of drug-naive children and adolescents

The aim of this prospective observational study was to investigate the variations of serum prolactin hormone (PRL) in a sample of 34 drug-naive patients (mean age 13 years) who started risperidone therapy assuming that several factors may favor the increase in serum PRL. Serum PRL and hyperprolactinemia clinical signs were examined at baseline (T0) and after almost 3 months of treatment (T1). We considered sex, pubertal status, risperidone dosage, psychiatric diagnosis, and any personal/family history of autoimmune diseases. The mean serum PRL value increased between T0 and T1 (P=0.004). The mean serum PRL was higher in females in the pubertal/postpubertal stage and for risperidone dosage up 1 mg/day. Hyperprolactinemia was found in 20% of patients at T0 and in 38% of patients at T1 (P=0.03). The mean serum PRL increase was greater in early-onset schizophrenia spectrum psychosis patients compared with no-early-onset schizophrenia spectrum psychosis patients (P=0.04). The increase in PRL was higher in patients with a personal and a family history of autoimmune diseases. This study suggests that the increase in serum PRL in patients treated with risperidone may be linked not only to the drug and its dosage but also to several risk factors such as sex, pubertal stage, psychiatric disease, and autoimmune disorders.

Clinical and pharmacokinetic evaluation of risperidone for the management of autism spectrum disorder

INTRODUCTION

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is often accompanied by psychiatric comorbidity. Although there is no medication currently available to treat the core symptoms of ASD, risperidone was the first drug to be approved for use in ASD and is still the best established psychopharmacological option for the treatment of irritability and behavioral problems in ASD.

AREAS COVERED

This article gives an overview of the pharmacokinetic profile of risperidone and a comprehensive review of treatment studies regarding the use of risperidone in ASD.

EXPERT OPINION

Ample evidence supports the short-term use of risperidone for treating irritability and behavioral problems in ASD. Risperidone also shows promise in treating symptoms often associated with ASD, such as stereotypical behavior, social difficulties, hyperactivity and cognitive problems. However, several adverse effects have been identified; most are mild or moderate and well manageable, but weight gain and metabolic changes are a considerable concern. Therefore, risperidone should in our view be seen as 'a last resort', only justified for the short-term treatment of serious behavioral problems, which have failed to respond sufficiently to behavioral interventions. Future studies should investigate long-term effects of risperidone and factors that facilitate individual risk-benefit analyses before treatment.

Effect of CYP2D6 on risperidone pharmacokinetics and extrapyramidal symptoms in healthy volunteers: results from a pharmacogenetic clinical trial

AIM

To elucidate the relationship between CYP2D6 genotype and risperidone pharmacokinetics and extrapyramidal symptoms we propose the APSEP pharmacogenetic clinical trial.

MATERIALS & METHODS

Twenty-five healthy subjects were included in this randomized, placebo-controlled, single dose (risperidone 2.5 mg) crossover and double-blind clinical trial. Subjects were selected according to their CYP2D6 genotype and classified as: poor metabolizers (n = 8), extensive metabolizers (n = 10) and ultrarapid metabolizers (n = 7).

RESULTS & CONCLUSION

Our study demonstrates that CYP2D6 predicted 65% of the risperidone metabolism variability. Moreover, its ability to predict actigraphy records is similar to the predictive power of pharmacokinetic parameters (24%). Our results also highlight the need for the development of pharmacogenetic predictors that take into account the complexity of pharmacokinetic and pharmacodynamic relationships.

Safety and pharmacokinetics of atypical antipsychotics in children and adolescents

Pediatric behavioral and affective disorders often require antipsychotic therapy, in combination with psychotherapeutic interventions, for their treatment and stabilization. Although pharmacotherapy can include either typical or atypical antipsychotics, the latter are generally preferred because of their apparently lower risk of adverse effects. Recent controlled trials have demonstrated the efficacy of some of these agents (including aripiprazole, clozapine, olanzapine, paliperidone, quetiapine, risperidone, ziprasidone) in adolescent schizophrenia and children or adolescent bipolar mania, or to treat severe aggression and self-injury in the context of autism in children and adolescents. Although few studies have systematically monitored their short- and, more importantly, long-term safety, current evidence indicates that sedation, hyperprolactinemia, and metabolic abnormalities such as excess weight gain, diabetes, and related cardiovascular effects were clinically relevant adverse effects in young patients, with the individual agents differing in their propensity to induce these effects. When prescribing antipsychotics for children and adolescents, physicians should therefore be aware of the specific adverse effect profiles and patients should be closely monitored for the short- and long-term development of adverse events. In pediatric patients, the starting dose, titration plan, and maintenance dose of antipsychotics must be based on their pharmacokinetics and metabolism, as in adults. Because there are significant individual differences in drug and active metabolite(s) pharmacokinetics and metabolism, which may be further affected by a number of confounding factors (including demographic variables, phenotype and drug interactions), therapeutic drug monitoring may be a valid tool for individualizing dosage, but its interpretation should also take account of changes in pharmacodynamic sensitivity with the development during childhood and adolescence.

DRD2 Taq1A polymorphism modulates prolactin secretion induced by atypical antipsychotics in healthy volunteers

Hyperprolactinemia mediated by antagonism of dopaminergic neurotransmission in the pituitary gland is a common adverse effect of antipsychotics. Recent studies have suggested that polymorphisms of dopamine receptors can affect the therapeutic response to antipsychotics. Thus, our aim was to evaluate whether 2 such polymorphisms (DRD2 Taq1A and DRD3 Ser9Gly) modulate prolactin release in healthy volunteers (n = 119) receiving a single dose of quetiapine (25 mg, n = 26), olanzapine (5 mg, n = 57), or risperidone (1 mg, n = 36). The increases in maximum concentration and in area under the curve were calculated from plasma prolactin levels after subtraction of pretreatment levels. Multiple regression analyses revealed that prolactin increases in maximum concentration and in area under the curve depended on drug (quetiapine < olanzapine < risperidone; P < 0.001), sex (women > men; P < 0.001), and Taq1A polymorphism (A1⁺ > A2/A2; P < 0.05). Analysis of the individual drugs revealed that prolactin secretion was modulated by sex and Taq1A polymorphism in olanzapine and risperidone (P < 0.05); however, these factors were not linked to prolactin secretion in quetiapine.

Second generation antipsychotics (SGAs) for non-psychotic disorders in children and adolescents: a review of the randomized controlled studies

In children and adolescents the Second Generation Antipsychotics (SGAs) represent the class of psychotropic drugs whose use has grown more significantly in recent years: they are primarily used for treatment of patients with disruptive behavior disorders, mood disorders and pervasive developmental disorders or mental retardation. In order to compare the efficacy and tolerability of antipsychotics against placebo or each other, a systematic Medline/PubMed search for randomized, double blind studies on SGA in patients younger than 18 years of age at enrollment, was conducted. Papers on schizophrenia, discussed in another article of this specific issue, were excluded by the efficacy analysis. A set of standard efficacy and safety indices, such as treatment effect sizes (ES), the Numbers Needed to Treat (NNT) and Numbers Needed to Harm (NNH), was used to compare medications. 32 studies analyzing efficacy and/or tolerability of SGAs in children and adolescents with bipolar, autistic or disruptive behavior disorders, and Tourette syndrome were identified. SGAs efficacy on mania, extreme mood variability, irritability, aggression and disruptive behavior appears to be greater than for psychotic symptoms in schizophrenia: average NNT was 2-5, whereas for schizophrenia it varies between 3 for risperidone and 10 for olanzapine, quetiapine, and aripiprazole. As for schizophrenia, different SGAs show a similar efficacy for specific non-psychotic disorders, but they significantly differ in their safety profile. In randomized studies, adverse effects were usually relatively minor, easily predictable and manageable, whereas long-term open-label studies have indicated that some adverse event, such as the metabolic effects, may be severe and potentially life threatening on the long-term. Taken together, these findings suggest that the choice of a specific treatment should be guided primarily by the safety profile of specific antipsychotics, considering specific risk factors (i.e. obesity and BMI, family history of diabetes or cardiovascular disorder, etc) for the single patient.

Effects of CYP2D6 genotype on the pharmacokinetics, pharmacodynamics, and safety of risperidone in healthy volunteers

The objective of this study was to analyze the relationship between CYP2D6 genotype and pharmacokinetics and pharmacodynamics of risperidone. Seventy-one healthy volunteers (36 women and 35 men) received a 1-mg single oral dose of risperidone. Six major CYP2D6 polymorphisms (CYP2D6*3, *4, *5, *6, *7, and *9) and the duplication were detected. Subjects were classified into 4 phenotypic groups: 6 ultrarapid (UMs), 34 extensive (EMs), 25 intermediate (IMs), and 6 poor metabolizers (PMs). There was a clear relationship between the number of active alleles and the pharmacokinetic parameters for risperidone and 9-hydroxyrisperidone, but there were no differences for total active moiety. Area under the curve and half-life of risperidone were significantly higher in PMs and IMs compared with EMs and UMs, which showed higher area under the curve of 9-hydroxyrisperidone. Risperidone produced a small decrease in blood pressure, a mild increase in QTc and a quick increase in prolactin, without significant differences between groups. Surprisingly, the incidence of adverse reactions was lower in PMs (50%) than in other subjects (78%). In conclusion, metabolism of risperidone depends on the number of active CYP2D6 alleles. So, PM subjects show higher concentrations of risperidone and very low concentrations of 9-hydroxyrisperidone. On the contrary, EM and UM subjects show low concentrations of risperidone and high concentrations of 9-hydroxyrisperidone. However, no major pharmacodynamic differences are observed between CYP2D6 genotypes, presumably because of the similar pharmacological activity of parent drug and metabolite.

Hyperprolactinemia with antipsychotic drugs in children and adolescents

There is increasing use of antipsychotic drugs in pediatric and psychiatry practice for a wide range of behavioral and affective disorders. These drugs have prominent side effects of interest to pediatric endocrinologists, including weight gain and associated metabolic risk factors and hyperprolactinemia. The drugs block dopamine action, thus disinhibiting prolactin secretion. Hyperprolactinemia is especially prominent with first-generation antipsychotics such as haloperidol and the second-generation drugs, most commonly risperidone, with some patients developing gynecomastia or galactorrhea or, as a result of prolactin inhibition of gonadotropin releasing hormone from the hypothalamus, amenorrhea. With concern about the long-term effects of antipsychotics on bone mass and pituitary tumor formation, it is prudent to monitor serum prolactin levels in antipsychotic drug-treated pediatric patients and consider treatment with an agent less likely to induce hyperprolactinemia.

A comparison of serum prolactin concentrations after administration of paliperidone extended-release and risperidone tablets in patients with schizophrenia

Increases in serum prolactin concentrations after administration of risperidone have been attributed, by some, to the availability of paliperidone in plasma. This double-blind, randomized, parallel-group study in patients with schizophrenia compared serum prolactin concentrations following the administration of paliperidone extended-release and risperidone immediate-release tablets. At steady state, the doses administered resulted in a similar exposure to paliperidone and the pharmacologically active fraction of risperidone (i.e. risperidone + paliperidone), respectively. Eligible patients were randomized to either paliperidone extended-release 12 mg on days 1-6 or risperidone immediate-release 2 mg on day 1 and 4 mg on days 2-6. Mean serum prolactin concentrations increased on day 1 (C(max): 71.8 ng/ml and 89.7 ng/ml reached at 6.5 hours and 2.6 hours for paliperidone extended-release and risperidone immediate-release, respectively). On day 6, serum prolactin concentration-time profiles were similar for both treatments, with overall higher serum prolactin concentrations than on day 1 (AUC(0-24 h): 1389 and 842 ng h/ml, and 1306 and 741 ng.h/ml on day 6 and day 1 for paliperidone extended-release and risperidone immediate-release, respectively). These results indicate that paliperidone extended-release 12 mg and risperidone immediate-release 4 mg, administered over a period of 6 days, lead to similar elevations in serum prolactin concentrations.

Short- and long-term effects on prolactin of risperidone and olanzapine treatments in children and adolescents

This study investigated prolactin levels in two groups of children and adolescents receiving risperidone (N=29) or olanzapine (N=13). It focused not only on significant differences but also on effect sizes; took into account dose effects and gender differences; used a longitudinal design (months 1, 3, 6 and 12) that helped control for individual differences; and took into account response differences due to the duration of antipsychotic treatment. Additionally, this study investigated tolerance development using statistical tests, and explored the effect of antipsychotic plasma concentrations at months 1 and 3. After adjusting for gender, treatment duration and individual effects, mean prolactin levels on risperidone were 4.9 ng/mL higher than on olanzapine (10.3 times higher after controlling for dosing potency). On risperidone treatment, the adjusted mean prolactin level at the 3rd month of treatment was significantly higher than at the 1st month; at the 12th month it was significantly lower than at the 1st month; the 1st and 6th months were not significantly different. On olanzapine treatment, adjusted mean prolactin levels at the 3rd and 6th months of treatment were significantly higher than at the 1st month; at the 12th month it was lower than at the 1st month, but the difference was not significant. In males, at the 3rd month, an increase of 1 ng/mL in plasma 9-hydroxyrisperidone concentrations raised prolactin levels significantly by 0.44 ng/mL. In females, independently of duration (1 or 3 months), an increase of 1 ng/mL in plasma olanzapine concentrations raised prolactin levels significantly by 2.1 ng/mL. After adjusting for dose and the greater potency of risperidone, the increase in prolactin levels during risperidone treatment appeared to be 10.3 times higher than that during olanzapine treatment. Our study showed a pattern consistent with the development of prolactin tolerance over time. Future prolactin studies in children and adolescents taking antipsychotics need to include larger samples with more frequent prolactin measures and long-term plasma concentrations.

Antipsychotic medication in children and adolescents: a descriptive review of the effects on prolactin level and associated side effects

OBJECTIVE

This review reports the incidence of hyperprolactinemia, its relationship with genotype, and prolactin-related side effects in children and adolescents treated with antipsychotics.

METHOD

Data on prolactin levels were available for haloperidol, pimozide, risperidone, olanzapine, clozapine, ziprasidone, and quetiapine. Twenty-nine studies were selected after a literature search in the English Medline/Embase/Psychinfo/EBM databases (1965 to August, 2008).

RESULTS

All antipsychotics, except clozapine, ziprasidone, and quetiapine, increase the mean prolactin level from baseline values of 8.0 ng/mL to 25-28 ng/mL after 4 weeks of treatment (reference range 0-15 ng/mL). The most and best data are available for risperidone. Five risperidone studies (n = 577) show an increase of prolactin level from 7.8 ng/mL to 17.7 ng/mL after 1 year of treatment, and two risperidone studies (n = 60) show an increase from 7.4 ng/mL to 24.9 ng/mL after 2 years of treatment. Aggregated over all antipsychotics, prolactin-related side effects, such as gynecomastia, galactorrhea, irregular menses, and sexual dysfunction, were reported by 4.8% of the children and adolescents. No data are available on bone mineral density in relation to antipsychotic-induced hyperprolactinemia in children and adolescents. Prolactin levels may be influenced by the genetic differences that influence prolactin metabolism and D2 dopamine receptor density.

CONCLUSION

Persistent elevation of prolactin for periods up to 2 years has been documented in maintenance treatment with risperidone. Very limited long-term data of pimozide, olanzapine, and quetiapine prohibit drawing conclusions for these antipsychotics. Systematic long-term observational studies, including specific questionnaires as well as physical examination, are needed to investigate prolactin-related side effects of antipsychotic treatment in children and adolescents.

Cytochrome P450 2D6 genotyping: potential role in improving treatment outcomes in psychiatric disorders

The specific reaction toward a given drug varies a lot between individuals and, for many drugs, pharmacogenetic polymorphisms are known to affect biotransformation and clinical outcome. Estimation of the individual's drug-metabolizing capacity can be undertaken by genotyping drug-metabolizing enzymes involved in the respective drug metabolism. Consequences that arise from genotyping may be the adjustment of dose according to genotype, choice of therapeutic strategy, or even choice of drug. One of the first fields where the clinical application of pharmacogenetics may be used is in that of antipsychotic and antidepressant drug treatment because there is a special need for individualized therapy in psychiatry. The pharmacokinetics of many TCAs, some SSRIs and other antidepressant drugs is significantly altered by polymorphisms; however, some controversy still exists as to whether therapeutic efficacy may be improved and/or adverse events can be prevented by genetically driven adjustment of drug dosage. Pharmacogenetic diagnostics may be an important factor in individualizing drug treatment according to the genetic make-up of the patients. However, routine application of pharmacogenetic dose adjustment in clinical practice requires prospective validation.

Variants of the dopamine D2 receptor gene and risperidone-induced hyperprolactinemia in children and adolescents

OBJECTIVE

To investigate the association between hyperprolactinemia and variants of the dopamine D2 receptor (DRD2) gene in children and adolescents in long-term treatment with risperidone.

METHODS

Medically healthy 7 to 17-year-old patients chronically treated with risperidone but receiving no other antipsychotics were recruited in a cross-sectional study. Four DRD2 variants were genotyped and prolactin concentration was measured. Medication history was obtained from the medical records. The effect of the TaqIA variants of the DRD2 on the risk of risperidone-induced hyperprolactinemia was the primary outcome measure.

RESULTS

Hyperprolactinemia was present in 50% of 107 patients (87% males) treated with risperidone for an average of 2.9 years. Age, stage of sexual development, and the dose of risperidone independently predicted a higher prolactin concentration, whereas the dose of psychostimulants was negatively correlated with it. However, these four predictors became nonsignificant when risperidone serum concentration was entered into the model. Adverse events potentially related to hyperprolactinemia were more common in participants with elevated prolactin concentration and in girls (45%) compared with boys (10%). After controlling for risperidone concentration and the dose of psychostimulants, the TaqIA A1 and the A-241G alleles were associated with higher prolactin concentration, whereas the -141C Ins/Del and C957T variants had no significant effect. In addition, adverse events potentially related to hyperprolactinemia were four times more common in TaqIA A1 allele carriers.

CONCLUSION

Prolactin concentration is closely related to central DRD2 blockade, as reflected by risperidone serum concentration. Furthermore, the TaqIA and A-241G variants of the DRD2 gene could be useful in predicting the emergence of hyperprolactinemia and its potential adverse events.

CYP2D6 genotyping for psychiatric patients treated with risperidone: considerations for cost–effectiveness studies

In order to ascertain data availability and feasibility for conducting cost–effectiveness studies in pharmacogenetics, and as part of a European Commission Joint Research Center, Institute for Prospective Technological Studies (JRC-IPTS) study, data concerning risperidone use and cytochrome P450 (CYP2D6) genotyping in medical care was collected in Germany, Spain and the USA, and are summarized in this perspective. The gene coding for CYP2D6 is highly polymorphic, resulting in a significant part of the population being poor metabolizers and ultrarapid metabolizers. Individuals who are CYP2D6 poor metabolizers, have an increased risk of adverse drug reactions (ADRs) when treated with CYP2D6-metabolized drugs, suggesting that CYP2D6 genotyping might be beneficial for patient care. This might be especially important in psychiatry, where approximately 50% of the patients use at least one drug primarily metabolized by CYP2D6. In particular, ADRs and poor response to treatment are major problems for some antipsychotics, including risperidone. However, there are no published cost–effectiveness studies on CYP2D6 genotyping, and the benefit that pharmacogenetic testing might represent by identifying problematic patients is still unclear. The present European Commission study found that current clinical and economical data concerning the frequency and direct healthcare costs of risperidone-related ADRs, the relation of such ADRs with the patients CYP2D6 genotypes, and costs for CYP2D6 genotyping, are not sufficient for determining if routine CYP2D6 genotyping might be cost beneficial for patients treated with risperidone. Therefore, efforts should be put on performing prospective cost–benefit studies with randomized treatment according to the CYP2D6 genotype to establish the utility of CYP2D6 genotyping for personalizing antipsychotic treatment.

[Risperidone use in child and adolescent psychiatric patients]

In a plural and multidisciplinary process of care, it would be fruitful to ally complementary, pharmacologic and psychodynamic approaches. We have done a review of the literature on the effectiveness and the cautions for prescription of risperidone, a second generation antipsychotic drug. Risperidone has proved helpful in treating children and adolescents with autism spectrum, conduct and bipolar disorders, Tourette's syndrome, and schizophrenia. The principal side effects are sedation, weight gain, and metabolic disturbances. Extrapyramidal symptoms, QTc prolongation, and hyperprolactemia with clinical signs are infrequent and not clinically significant. The benefit/risk is clearly in favor of the prescription when it is accompanied with the precautions and with the adequate monitoring.

Relationship between prolactin secretion, and plasma risperidone and 9-hydroxyrisperidone concentrations in adolescents with schizophreniform disorder

BACKGROUND

Treatment with the atypical antipsychotic risperidone can result in elevated prolactin levels. To date, the relationships between plasma concentrations of prolactin, risperidone and its active 9-hydroxy-metabolite have been little investigated in adolescents with psychosis.

METHODS

Prolactin levels were determined at baseline in 16 hospitalized drug-naïve adolescents meeting DSM-IV criteria for schizophreniform disorder. Prolactin, risperidone, 9-hydroxyrisperidone levels were subsequently determined after 3 weeks of oral risperidone treatment.

RESULTS

Compared with pretreatment values, prolactin levels at endpoint were significantly increased (p<0.00001) and correlated with risperidone doses (r=0.58, N=16, p<0.02), and plasma levels of risperidone (r=0.60, N=16, p<0.02) and 9-hydroxyrisperidone (r=0.54, N=16, p=0.03).

CONCLUSIONS

These data suggest that risperidone's effect on prolactin release is dose-dependent in adolescents and is linked to both plasma risperidone and 9-hydroxyrisperidone concentrations.

Pharmacogenetics of risperidone response and induced side effects

Risperidone is an atypical antipsychotic that has been effectively used to treat several psychiatric diseases. Atypical antipsychotics present some advantages over conventional antipsychotics, primarily because they offer effective treatment alternatives that are relatively free of extrapyramidal symptoms. However, as with all antipsychotics, there are wide individual differences in response to risperidone, both regarding therapeutic effects and adverse effects, imposing some limitations with respect to the therapeutic use of the drug. Genetic factors are thought to play an important role in determining the variability to drug response. A growing number of studies are investigating how genetic polymorphisms of enzymes involved in drug metabolism or of receptors targeted by antipsychotic agents influence drug treatment of several neuropsychiatric diseases. In this article we will review the genetic variability in both the pharmacokinetics of risperidone action and in pharmacodynamic structures mediating risperidone effects, as well as the pharmacogenetic studies performed for these genes.