Possible relationship between combined plasma concentrations of risperidone plus 9-hydroxyrisperidone and extrapyramidal symptoms. Preliminary study

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

BACKGROUND

Prior studies have noted great variability in the plasma levels of risperidone (RIS). Plasma concentrations of RIS and its active moiety are highly variable and depend on absorption, metabolism, and other predictors of metabolic dysregulation; however, these factors are poorly understood and the association between metabolic change and change in psychopathology is uncertain.

AIM

To ascertain the characteristics of chronic schizophrenic patients treated with RIS, and to assess their relationship with plasma RIS levels.

METHODS

This was a descriptive cross-sectional study of 50 patients with a diagnosis of schizophrenic psychosis treated with RIS in a psychiatric service. The plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone were determined by high performance liquid chromatography. The patients' demographic and clinical characteristics, and psychopathologies were assessed, and the associations between clinical variables and plasma levels of RIS were explored.

RESULTS

Male patients received higher doses of RIS than female ones, but plasma concentrations of RIS and risperidone + 9-hydroxyrisperidone (active moiety) were higher in female patients. Age and the mean scores of the general psychopathology subscale of the Positive and Negative Syndrome Scale (PANSS) were significantly positively correlated with plasma concentrations of risperidone + 9-hydroxyrisperidone adjusted for weight and dose in all 50 subjects. In male subjects, we found a statistically significant positive correlation between the concentrations of risperidone + 9-hydroxyrisperidone in plasma/(dose × kg) and age, mean PANSS negative subscale scores, mean PANSS general psychopathology subscale scores, and mean PANSS total scores.

CONCLUSION

Long-term use of RIS should be closely monitored in older patients and females to minimize the risk of high concentrations which could induce side effects.

Risperidone plasma level, and its correlation with CYP2D6 gene polymorphism, clinical response and side effects in chronic schizophrenia patients

BACKGROUND

To explore the influence of CYP2D6 genetic polymorphism on risperidone metabolism, thereby affecting risperidone's effects and safeties in patients with chronic schizophrenia.

METHODS

Sixty-nine subjects with chronic schizophrenia treated with risperidone were recruited. CYP2D6 genotypes was determined using targeted sequencing and translated into phenotype using activity system. Risperidone plasma concentrations were measured using HPLC. Positive and Negative Symptom Scale (PANSS) and Brief Psychiatric Rating Scale (BPRS) were used to evaluate the existence and severity of psychiatric symptoms, Barnes Akathisia Scale (BAS) and Extrapyramidal Symptom Rating Scale (ESRS) for neurological side effects. Metabolic and endocrine status assess were also included.

RESULTS

The plasma drug concentrations varied hugely among individuals. Intermediate metabolizer (IM) group had higher plasma levels of RIP and dose corrected RIP concentration, RIP/9-OH-RIP ratio and C/D ratio than normal metabolizer (NM) group (p < 0.01). There was no statistic difference between responders and non-responders in dose-adjusted plasma concentrations and ratios of RIP/9-OH-RIP and C/D. The occurrence of EPS was related to active moiety levels in 4th week (p < 0.05). The prolactin (PRL) levels in two follow-ups were both significantly higher than baseline (p < 0.01). PRL change from baseline to week 4 and week 8 were both positively associated with active moiety concentration detected in week 4 (p < 0.05).

CONCLUSIONS

The risperidone plasma levels have great inter- and intraindividual variations, and are associated with the CYP2D6 phenotypes, as well as the changes in serum prolactin in patients diagnosed with chronic schizophrenia.

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.

Differences in autonomic nervous system activity between long-acting injectable aripiprazole and oral aripiprazole in schizophrenia

BACKGROUND

Distinct oral atypical antipsychotics have different effects on autonomic nervous system (ANS) activity. Among them, oral aripiprazole has been linked to dysfunction of the ANS in schizophrenia. Long-acting injectable aripiprazole is a major treatment option for schizophrenia, but the effect of the aripiprazole formulation on ANS activity remains unclear. In this study, we compared ANS activity between oral aripiprazole and aripiprazole once-monthly (AOM) in schizophrenia.

METHODS

Of the 122 patients with schizophrenia who participated in this study, 72 received oral aripiprazole and 50 received AOM as monotherapy. We used power spectral analysis of heart rate variability to assess ANS activity.

RESULTS

Patients who received oral aripiprazole showed significantly diminished sympathetic nervous activity compared with those who received AOM. Multiple regression analysis revealed that the aripiprazole formulation significantly influenced sympathetic nervous activity.

CONCLUSION

Compared with oral aripiprazole, AOM appears to have fewer adverse effects, such as sympathetic nervous dysfunction.

Selective Spectrofluorimetric Approach for the Assessment of Two Antipsychotic Drugs through Derivatization with O-Phthalaldehyde

A facile and sensible spectrofluorimetric approach for the measurement of two antipsychotic medications, aripiperazole (ARP) and clozapine (CLZ), was devised and validated. The approach involves reacting the examined medicines with o-phthalaldehyde in the presence of β-mercaptoethanol in a borate buffer of pH 9.0 and pH 10 for ARP and CLZ, respectively, to produce a robustly fluorescent compound that is detected at 450 nm following excitation at 340 nm. The experimental variables influencing the performance and product stability were thoroughly investigated and optimized. Under optimal conditions, the intensity of the fluorescence was linear during a concentration range of 0.1–0.5 μg/mL, with a limit of detection (0.0391 and 0.0400 μg/mL) and limit of quantitation (0.1035 and 0.1332 μg/mL), respectively, for ARP and CLZ. The suggested approach was successful in analyzing commercialized tablets. A statistical investigation of the results produced by the suggested and standard methods showed no remarkable variation in the precision and accuracy of the two approaches. A chemical mechanism using o-phthalaldehyde was proposed.

Optimization of maintenance therapy of Risperidone with CYP2D6 genetic polymorphisms through an extended translational framework-based prediction of target occupancies/clinical outcomes

Risperidone, one of the second-generation antipsychotics, can efficiently target dopamine D₂ and serotonin 5-HT_2A receptors. There actually exists significant implication of CYP2D6 genetic polymorphisms on the metabolic kinetics of risperidone, little is known about the extent of CYP2D6 impacting human D2 and 5-HT2A receptor occupancies as well as the clinical efficacy and efficacy in schizophrenia treatment. Here we assessed the influences of CYP2D6 gene polymorphisms on human target occupancies/clinical outcomes and optimized the maintenance therapy of risperidone. A translational framework, previously developed using in vitro and in vivo information in rats, was used as the basis for integrating the effects of CYP2D6 genetic polymorphisms on target occupancies and clinical outcomes. D₂ occupancy as a biomarker was related to Positive and Negative Syndrome Scale (PANSS) response and Simpson-Angus Scale (SAS). The population approach was applied to characterize pharmacokinetic and pharmacodynamic (PK/PD) profiles of risperidone. Non-compartment analysis method was performed to calculate the steady state PK/PD parameters of both risperidone and 9-hydroxyrisperidone. The predictive power of this extended translational framework was determined by comparing the predictions of target occupancies and clinical outcomes with the reported human values of risperidone at clinically suggested dosage of 4.0 mg/day. This extended translational framework was adequately used to predict human target occupancies and clinical outcomes. At the steady state, D₂ ROs were 75.8%, 79.3% and 86.0% for CYP2D6 poor metabolizer (PM), intermediate metabolizer (IM) and extensive metabolizer (EM), respectively; 5-HT_2A ROs were 96.4%, 97.2% and 98.4% for CYP2D6 PM, IM and EM, respectively; PANSS changes from placebo were -5.3, -7.7 and -11.3 for CYP2D6 PM, IM and EM, respectively; SAS changes from placebo were 0.13, 0.15 and 0.18 for CYP2D6 PM, IM and EM, respectively. The predictions of human D₂, 5-HT_2A RO, PANSS and SAS changes for risperidone with CYP2D6 genetic polymorphisms were well in line with the reported values in clinic. 5.0, 4.0 and 2.5 mg/day were the equivalent dosages of risperidone for CYP2D6 PM, IM and EM, respectively. The optimized maintenance therapy of risperidone was provided through the Three-Step method and the dosage range was 2.5-5.0 mg/day for three CYP2D6 gene groups in the present study. Taken together, our findings demonstrate that this extended translational framework not only differentiates the effects of CYP2D6 genetic polymorphisms on target occupancies and clinical outcomes, but also constitutes a scientific basis to optimize the maintenance therapy of neuropsychiatric patients in clinic.

Effects of long-acting injectable antipsychotics versus oral antipsychotics on autonomic nervous system activity in schizophrenic patients

OBJECTIVE

Long-acting injections (LAIs) of antipsychotics show distinct pharmacokinetic profiles from oral antipsychotics (OAPs). Although there may be differences in adverse event frequency, any differences in their effects on autonomic nervous system (ANS) remain unclear.

PATIENTS AND METHODS

In total, 270 schizophrenic patients were recruited in this study: 241 received OAPs (risperidone, olanzapine, quetiapine, or aripiprazole) and 29 received LAIs (risperidone LAI, aripiprazole LAI, or paliperidone palmitate) as monotherapy. Heart rate variability was measured as an index of ANS activity, and the low-frequency (0.03-0.15 Hz) component, high-frequency (0.15-0.40 Hz) component, and total power (0.03-0.40 Hz) were calculated. Components were compared between the groups using t-tests.

RESULTS

A significant difference was detected in the low-frequency component between the OAP and LAI groups (P=0.046). No significant difference was found in total power or the high-frequency component between the two groups.

CONCLUSION

Compared with OAPs, LAIs have fewer adverse effects on ANS activity, particularly the low-frequency component, as determined using a spectral analysis of heart rate variability.

Dried Blood Spots Combined With Ultra-High-Performance Liquid Chromatography-Mass Spectrometry for the Quantification of the Antipsychotics Risperidone, Aripiprazole, Pipamperone, and Their Major Metabolites

BACKGROUND

Risperidone, aripiprazole, and pipamperone are antipsychotic drugs frequently prescribed for the treatment of comorbid behavioral problems in children with autism spectrum disorders. Therapeutic drug monitoring (TDM) could be useful to decrease side effects and to improve patient outcome. Dried blood spot (DBS) sample collection seems to be an attractive technique to develop TDM of these drugs in a pediatric population. The aim of this work was to develop and validate a DBS assay suitable for TDM and home sampling.

METHODS

Risperidone, 9-OH risperidone, aripiprazole, dehydroaripiprazole, and pipamperone were extracted from DBS and analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry using a C18 reversed-phase column with a mobile phase consisting of ammonium acetate/formic acid in water or methanol. The suitability of DBS for TDM was assessed by studying the influence of specific parameters: extraction solution, EDTA carryover, hematocrit, punching location, spot volume, and hemolysis. The assay was validated with respect to conventional guidelines for bioanalytical methods.

RESULTS

The method was linear, specific without any critical matrix effect, and with a mean recovery around 90%. Accuracy and imprecision were within the acceptance criteria in samples with hematocrit values from 30% to 45%. EDTA or hemolysis did not skew the results, and no punching carryover was observed. No significant influence of the spot volume or the punch location was observed. The antipsychotics were all stable in DBS stored 10 days at room temperature and 1 month at 4 or -80°C. The method was successfully applied to quantify the 3 antipsychotics and their metabolites in patient samples.

CONCLUSIONS

A UHPLC-MS/MS method has been successfully validated for the simultaneous quantification of risperidone, 9-OH risperidone, aripiprazole, dehydroaripiprazole, and pipamperone in DBS. The assay provided good analytical performances for TDM and clinical research applications.

Risperidone-induced extrapyramidal side effects: is the need for anticholinergics the consequence of high plasma concentrations?

Antipsychotic drugs can induce various undesirable adverse motor reactions, such as extrapyramidal side effects (EPS). A widely accepted pharmacodynamic mechanism underlying EPS includes an increase in striatal D2-receptor occupancy. However, less is known about the pharmacokinetic background of EPS. The aim of this study was to analyze in-vivo possible pharmacokinetic patterns underlying biperiden-treated EPS in risperidone (RIS)-medicated patients. A large therapeutic drug monitoring database containing plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone (9-OH-RIS) of 2293 adult inpatients and outpatients was analyzed. Two groups were compared: a group receiving RIS (n=772) and a group comedicated with biperiden (n=68). Plasma concentrations, dose-adjusted plasma concentrations (C/D) of RIS, 9-OH-RIS, and active moiety (AM) (RIS+9-OH-RIS) as well as ratios of concentrations for metabolite to parent drug (9-OH-RIS/RIS) were computed. We compared the plasma concentrations of the different compounds between the two groups considering the prescription of biperiden as an indirect report of EPS. The daily dosage of RIS did not differ between groups. No differences were detected in case of plasma concentrations and C/D of RIS and active metabolite between the groups. However, plasma concentrations of the AM were significantly higher in the comedicated group (P=0.032) and showed a trend in terms of the active metabolite 9-OH-RIS (P=0.053). Data indicate enhanced AM plasma concentrations of RIS in patients comedicated with biperiden as an EPS treatment. This might underscore an association between higher plasma concentrations of the AM and treatment-requiring EPS.

An analysis of potentially prolactin-related adverse events and abnormal prolactin values in randomized clinical trials with paliperidone palmitate

BACKGROUND

Paliperidone palmitate has been associated with serum prolactin elevations in some patients. However, few individuals with elevated prolactin levels (hyperprolactinemia) have symptomatic potentially prolactin-related adverse events (PPR-AEs).

OBJECTIVE

To quantify rates of hyperprolactinemia in subjects treated with the newly marketed paliperidone palmitate long-acting injection (PP-LAI) in randomized clinical trials, summarize rates of PPR-AEs in those trials by sex and dose, and determine how many PPR-AEs required treatment.

METHODS

Numbers and rates of investigator-reported hyperprolactinemia and PPR-AEs were obtained from the sponsor's clinical trial database and have been included in regulatory filings. Results were tabulated for males, females, and overall, and by dose administered, using descriptive statistics. Those requiring treatment were described as well.

RESULTS

There were 3173 subjects (61.4% males) exposed to PP-LAI in 10 clinical trials; 2831 (89.2%) patients had recorded prolactin levels, including 1759 males (90.3% of exposed males) and 1072 females (87.5% of exposed females). Overall, at any time, prolactin levels were elevated for 38.8% of the subjects (39.5% for males and 37.7% for females; p = 0.354 between sexes). However, there was no significant correlation between monthly dose and proportion of subjects with elevated prolactin levels (p = 0.109). There were 115 PPR-AEs in 107 patients (3.4%); 51 (44.3% of PPR-AEs) cases represented asymptomatic hyperprolactinemia. The remaining 64 symptomatic PPR-AEs affected 2.0% of the total number of subjects. Fifteen events in 13 participants (0.41% of patients or 4.7 events/1000 patients) required treatment.

CONCLUSIONS

Clinicians should periodically assess patients on paliperidone palmitate for any PPR-AEs and carefully assess the benefits and risks when managing these effects.

Comparing the influence of dopamine D₂ polymorphisms and plasma drug concentrations on the clinical response to risperidone

Although several studies have reported that dopamine D₂ receptor (DRD2) polymorphisms affect the therapeutic efficacy of antipsychotics, other studies have suggested that the plasma drug concentration is related to the clinical response. Currently, there are no definitive data regarding which factor has greater clinical significance. Sixty patients with acute exacerbations of schizophrenia received 6 mg/d of risperidone for 4 weeks. Clinical evaluations using the Brief Psychiatric Rating Scale and the Udvalg for Klinicke Undersøgelser Side Effect Rating Scale were performed before and after administration of risperidone. TaqI A and -141C Ins/Del polymorphisms were determined, and the plasma concentrations of risperidone and 9-hydroxyrisperidone were measured. The TaqI A polymorphism had no effect on therapeutic efficacy, but the -141C Ins/Del polymorphism was associated with an improvement in positive symptoms. In addition, the plasma concentration of the active moiety (risperidone plus 9-hydroxyrisperidone) correlated with the improvement in the total Brief Psychiatric Rating Scale score as well as with positive symptoms. Although there were no associations between DRD2 polymorphisms and psychic adverse effects, the plasma drug concentration was associated with psychic adverse effects. These findings suggest that DRD2 polymorphisms are associated with the therapeutic effects of risperidone as they relate to positive symptoms and that plasma drug concentrations are associated with overall symptoms as well as excitement and cognitive symptoms. Both the genotyping of DRD2 and the monitoring of plasma drug concentrations may be useful for improving clinically dominant symptoms. Further work involving replication in a larger sample is required to support our findings.

A population pharmacokinetic evaluation of the influence of CYP2D6 genotype on risperidone metabolism in patients with acute episode of schizophrenia

The objective of this prospective study was to characterize the metabolism of risperidone to (+)- and (-)-9-hydroxyrisperidone in vivo and to evaluate the influence of CYP2D6 genotype. A population pharmacokinetic modeling approach was used to estimate the interindividual variability of the pharmacokinetic parameters in 50 hospitalized patients with acute episode of schizophrenia. CYP2D6 genotype remarkably influenced the formation clearances of the risperidone metabolites, while creatinine clearance was related to the plasma clearance of 9-hydroxyrisperidone. CYP2D6 genotype was also associated with the average plasma concentration of risperidone active moiety (a sum of all three active compounds). In comparison to the patients with CYP2D6*1/*1 genotype, average steady-state plasma concentration of risperidone active moiety was 3.3- and 1.6-fold higher in poor metabolizers (both alleles nonfunctional; CYP2D6*3 or *4) and intermediate metabolizers (one nonfunctional allele and one allele for diminished enzyme activity; CYP2D6*10 or *41), respectively. Additionally, average plasma concentration of risperidone active moiety was higher in the patients with dystonia (p=0.0066) and parkinsonism (p=0.046). The results of this study imply the potential role of CYP2D6 genotyping in personalizing risperidone therapy in patients with schizophrenia to reduce the incidence of adverse extrapyramidal symptoms.

Clinical response to risperidone in relation to plasma drug concentrations in acutely exacerbated schizophrenic patients

There are no data indicating a clear relationship between the clinical effect of risperidone and plasma drug concentration. In this study, 51 patients with acutely exacerbated schizophrenia received 6 mg risperidone/day for 4 weeks. A clinical evaluation using the Brief Psychiatric Rating Scale (BPRS) and Udvalg for Klinicke Undersøgelser (UKU) side effect rating scale were performed at baseline and each week. Significant (P < 0.05) correlations were found between plasma concentrations of risperidone and improved total BPRS scores, positive and cognitive symptoms. Plasma concentrations of the active moiety were significantly (P < 0.05) correlated with improved total BPRS scores. Improved score and percent improvement in anxiety-depression subscale were significantly (P < 0.01) correlated with plasma concentrations of the active moiety. The sum of total UKU side effect scores from 1 to 4 weeks was significantly correlated with plasma concentration of both risperidone (rs = 0.319, P < 0.05) and active moiety (rs = 0.373, P < 0.01). The sum of the psychic subgroup scores was significantly correlated with plasma concentrations of active moiety (rs = 0.318, P < 0.05). Results suggest that plasma drug concentrations are, to some extent, associated with improved scores in some psychopathological schizophrenic symptoms and sedative side effects. These findings should be replicated with a larger patient sample.

The role of CYP2D6 and ABCB1 pharmacogenetics in drug-naïve patients with first-episode schizophrenia treated with risperidone

PURPOSE

To evaluate the role of cytochrome 450 2D6 (CYP2D6) and ABCB1 variants on plasma risperidone concentrations and treatment response in 83 drug-naive patients experiencing a first episode of psychosis.

METHODS

All patients were treated with risperidone for 8 weeks. The CYP2D6 genotyping was performed by allele-specific PCR-restriction fragment length polymorphism analysis (for alleles *3,*4,*6) and long-distance PCR (for duplications and allele *5), while real-time PCR analysis was used for the ABCB1 G2677T/A and C3435T variants. Plasma concentrations of risperidone and 9-OH risperidone were measured by high-performance liquid chromatography.

RESULTS

The number of patients with the CYP2D6 wild type (wt)/wt, wt/mutation (mut) and mut/mut genotype was 43, 32 and 8, respectively. The number of patients with the ABCB1 2677G/G, G/T and T/T variants was 29, 42 and 12, respectively; those with the 3435CC, C/T and T/T variants was 25, 37 and 21, respectively. The CYP2D6 genotype had a strong effect on the steady-state dose-corrected plasma levels (C/D) of risperidone, its 9-OH metabolite and the active moiety, while the ABCB1 2677 T/T and 3435 T/T genotypes has similarly strong effects on the active moiety C/D. The CYP2D6 poor metabolizers had a significantly higher risperidone C/D and active moiety C/D and lower 9-OH risperidone C/D. The ABCB1 3435 T allele and the ABCB1 2667 T-3435 T haplotype carriers were more frequent among subjects without extrapyramidal syndromes. Patients showed significant improvements in positive and general symptoms, but not in negative symptoms. These changes were not related to variations in genetic and drug concentration data.

CONCLUSION

Our findings suggest that CYP2D6 and ABCB1 G2677T and C3435T may be useful determinants of risperidone plasma concentrations, but the clinical implications of these associations in relation to treatment response and side-effects remain unclear.

MDR1 gene polymorphisms and response to acute risperidone treatment

Polymorphic multidrug resistant protein 1 (MDR1) transports drugs against a concentration gradient across the blood-brain barrier and reduces their accumulation in the brain. MDR1 may therefore influence antipsychotic brain availability contributing to inter-individual differences in treatment response and adverse effects, regardless of plasma concentrations. In the present study we investigated the influence of two common MDR1 polymorphisms on the improvement of psychopathological symptoms and occurrence of extrapyramidal side effects (EPS) in Slovenian schizophrenia patients acutely treated with risperidone. A total of 59 clinically well defined patients with first episode schizophrenia spectrum disorders or after tapering their maintenance treatment were genotyped for MDR1 C3435T and G2677T/A. Steady-state plasma concentrations of risperidone active moiety (sum of risperidone and the 9-hydroxyrisperidone) were determined. G2677T/A and C3435T genotypes were not associated to psychopathological symptoms, efficacy of treatment and risk for parkinsonism. Marginal associations with akathisia (p=0.039 and p=0.042, respectively) and dystonia (p=0.013 and p=0.034, respectively) were observed for both G2677T/A and C3435T genotypes. However, higher AIMS and BARS scores were observed only in heterozygous carriers of G2677T/A and C3435T polymorphisms and there was no tendency of gene-dose effect. The present study does not suggest a major influence of MDR1 G2677T/A and C3435T polymorphisms on treatment response during short-term risperidone therapy in patients with schizophrenia or schizoaffective disorder.

Comparison of plasma levels between oral solution and fine granule dosage forms of risperidone

Objective. In Japan, there are several clinical reports that risperidone (RIS) oral solution (OS) requires shorter time for tranquilization and induces fewer extrapyramidal symptoms (EPS) than other dosage forms; i.e. fine granules (FG). Our aim is to compare plasma levels of RIS, its active metabolite (9-OH-RIS), and their sum (active moiety; AM) between RIS-OS and RIS-FG in a multiple-dose regimen. Method. A 12-week cross-over study was conducted in nine patients with schizophrenia treated with 3 mg of RIS twice daily. The study period was divided into four terms, each term being 3 weeks. RIS-FG and RIS-OS were given in two alternate terms each. Blood samples were collected on the last day of each term just before and at 1 h after RIS treatment to measure plasma levels of RIS, 9-OH-RIS, and prolactin. Result. Plasma levels of RIS, 9-OH-RIS, AM, and prolactin before treatment were significantly lower for RIS-OS than for RIS-FG, while no significant difference was observed between the two forms at 1 h after administration. Conclusion. In a multiple-dose regimen, RIS-OS treatment caused a larger diurnal fluctuation in plasma level of AM than RIS-FG. These variations may explain the differences in severity of EPS between the 2 forms.

Addition of risperidone to sertraline improves sertraline-resistant refractory depression without influencing plasma concentrations of sertraline and desmethylsertraline

In the present study, we examined the efficacy of risperidone addition on sertraline-resistant depressed patients and the effects of risperidone on the metabolism of sertraline. Ten patients (M/F: 4/6, age: 54 +/- 10 years) met the DSM-IV criteria for major depressive disorder enrolled the study. Hamilton Dating Scale for Depression (HAM-D) scores (mean +/- SD) in all 10 patients significantly decreased from 19 +/- 4 (before risperidone addition) to 11 +/- 3 (4 weeks after risperidone addition). Plasma levels of sertraline and desmethylsertraline did not change after risperidone addition. Serum BDNF levels in responders to risperidone addition were changed from 8.1 +/- 2.7 ng/ml (before risperidone addition) to 11.5 +/- 0.9 ng/ml (4 weeks after risperidone addition); in contrast, those in nonresponders changed from 7.8 +/- 2.2 ng/ml (before risperidone addition) to 7.9 +/- 2.4 ng/ml (4 weeks after risperidone addition). These results suggest that the addition of risperidone to sertraline is effective and well tolerated for sertraline-resistant depressive patients, which is accompanied with the increase in serum BDNF levels in responders to the risperidone addition, and the addition of risperidone to sertraline does not seem to influence sertraline metabolism.

Iloperidone: a new benzisoxazole atypical antipsychotic drug. Is it novel enough to impact the crowded atypical antipsychotic market?

Iloperidone is a new-generation atypical antipsychotic agent, acting as a serotonin/dopamine (5-HT(2A)/D(2)) antagonist, under development by Vanda Pharmaceuticals for the treatment of schizophrenia, bipolar disorder and other psychiatric conditions. Chemically, iloperidone is a benzisoxazole, like risperidone, and shows a multiple receptor binding profile, sharing this feature with the other atypical antipsychotic agents. Administered orally, the drug is highly bound to plasma proteins and extensively metabolised. Several clinical trials have been carried out, to check efficacy, safety and side effects. In order to introduce iloperidone as an agent for the treatment of schizophrenia, a short overview of the disease and of the most important antipsychotic drugs available or under development will be reported. Iloperidone pharmacokinetics and pharmacodynamics are presented herein, together with an evaluation of clinical safety and efficacy results.

Plasma pharmacokinetic characteristics of risperidone and their relationship to saliva concentrations in children with psychiatric or neurodevelopmental disorders

BACKGROUND

Risperidone is a second-generation antipsychotic agent widely used in the treatment of schizophrenia and other psychotic disorders in adults. Risperidone is probably the most frequently used atypical antipsychotic in the pediatric population.

OBJECTIVES

The goals of this study were to estimate the pharmacokinetic parameters of risperidone and its enantiomers in a pediatric population and explore relationships between saliva and plasma concentrations.

METHODS

Eligible patients, between 4 and 15 years of age, included those taking a stable dose of oral risperidone ranging from 0.01 to 0.07 mg/kg BID for > or =4 weeks to treat psychiatric or neurodevelopmental conditions. A trough blood level and predose saliva sample were collected at study initiation; the regular risperidone dose was administered; and paired samples of blood and saliva were collected at 1, 2, 4, and 7 hours postdose. Plasma/saliva concentrations of risperidone and enantiomers of its principal active metabolite, 9-hydroxyrisperidone (9-OH-risperidone), were measured using a chiral liquid chromatography-tandem mass spectrometry assay. Standard pharmacokinetic parameters were calculated. Cytochrome P450 2D6 genotypes of *3,*4,*5 deletion and duplication were determined.

RESULTS

The study included 19 patients (age range, 4 years 2 months to 15 years 11 months). Mean (SD) values for C(max), t(1/2), and AUC 0 to 12 hours for risperidone in plasma were 15.9 (22.2) ng/mL, 3.0 (2.3) h, and 92.1 (200.6) ng x h/mL, respectively. Corresponding values in saliva were 12.0 (21.0) ng/mL, 3.4 (3.2) h, and 27.8 (38.7) ng x h/mL, respectively. Mean (SD) plasma enantiomer values for C(max) and AUC calculated up to the last observation were: (+)-9-OH-risperidone, 13.6 (10.0) ng/mL and 73.6 (52.3) ng x h/mL; (-)-9-OH-risperidone, 4.9 (3.1) ng/mL and 29.3 (19.1) ng x h/mL. Corresponding enantiomer values in saliva were: (+)-9-OH-risperidone, 5.2 (8.8) ng/mL and 15.6 (8.9) ng x h/mL; (-)-9-OH-risperidone, 5.0 (7.9) ng/mL and 15.6 (9.1) ng x h/mL, respectively. Large interindividual variability in risperidone and enantiomer concentrations was noted. A highly significant relationship between predose plasma and predose saliva risperidone concentrations was observed. The logarithmic regression model indicated that the log risperidone saliva concentration = -0.100 + 0.594 x log plasma concentration (R(2) = 0.93 [Spearman]).

CONCLUSIONS

In this preliminary pharmacokinetic study of parameters for risperidone and the enantiomers of 9-OH-risperidone in a pediatric population, mean C(max) and t(1/2) of risperidone were generally similar to those previously described in adults. The highly significant relationship between predose plasma and predose saliva risperidone concentrations suggests that saliva measurements may be a viable alternative to plasma sampling in children.

Clinical Pharmacokinetics of Atypical Antipsychotics

In the past, the information about the dose-clinical effectiveness of typical antipsychotics was not complete and this led to the risk of extrapyramidal adverse effects. This, together with the intention of improving patients' quality of life and therapeutic compliance, resulted in the development of atypical or second-generation antipsychotics (SGAs). This review will concentrate on the pharmacokinetics and metabolism of clozapine, risperidone, olanzapine, quetiapine, amisulpride, ziprasidone, aripiprazole and sertindole, and will discuss the main aspects of their pharmacodynamics. In psychopharmacology, therapeutic drug monitoring studies have generally concentrated on controlling compliance and avoiding adverse effects by keeping long-term exposure to the minimal effective blood concentration. The rationale for using therapeutic drug monitoring in relation to SGAs is still a matter of debate, but there is growing evidence that it can improve efficacy, especially when patients do not respond to therapeutic doses or when they develop adverse effects. Here, we review the literature concerning the relationships between plasma concentrations of SGAs and clinical responses by dividing the studies on the basis of the length of their observation periods. Studies with clozapine evidenced a positive relationship between plasma concentrations and clinical response, with a threshold of 350-420 ng/mL associated with good clinical response. The usefulness of therapeutic drug monitoring is well established because high plasma concentrations of clozapine can increase the risk of epileptic seizures. Plasma clozapine concentrations seem to be influenced by many factors such as altered cytochrome P450 1A4 activity, age, sex and smoking. The pharmacological effects of risperidone depend on the sum of the plasma concentrations of risperidone and its 9-hydroxyrisperidone metabolite, so monitoring the plasma concentrations of the parent compound alone can lead to erroneous interpretations. Despite a large variability in plasma drug concentrations, the lack of studies using fixed dosages, and discrepancies in the results, it seems that monitoring the plasma concentrations of the active moiety may be useful. However, no therapeutic plasma concentration range for risperidone has yet been clearly established. A plasma threshold concentration for parkinsonian side effects has been found to be 74 ng/mL. Moreover, therapeutic drug monitoring may be particularly useful in the switch between the oral and the long-acting injectable form. The reviewed studies on olanzapine strongly indicate a relationship between clinical outcomes and plasma concentrations. Olanzapine therapeutic drug monitoring can be considered very useful in assessing therapeutic efficacy and controlling adverse events. A therapeutic range of 20-50 ng/mL has been found. There is little evidence in favour of the existence of a relationship between plasma quetiapine concentrations and clinical responses, and an optimal therapeutic range has not been identified. Positron emission tomography studies of receptor blockade indicated a discrepancy between the time course of receptor occupancy and plasma quetiapine concentrations. The value of quetiapine plasma concentration monitoring in clinical practice is still controversial. Preliminary data suggested that a therapeutic plasma amisulpride concentration of 367 ng/mL was associated with clinical improvement. A therapeutic range of 100-400 ng/mL is proposed from non-systematic clinical experience. There is no direct evidence concerning optimal plasma concentration ranges of ziprasidone, aripiprazole or sertindole.

Effects of chronic risperidone treatment on the striatal protein profiles in rats

Extrapyramidal symptoms (EPS) commonly occur as side effects of antipsychotic drugs (APDs) and are most likely to arise when the occupancy of dopamine D(2) receptors in the striatum by these drugs exceeds 80%. We aimed to characterize changes in the protein expression profile in the striatum of rats after chronic (4 week) supra-therapeutic (EPS-inducing) treatment with risperidone (RIS), an atypical antipsychotic drug. Administration of RIS (2.1 mg/kg/day, via subcutaneous osmotic minipumps) induced significant vacuous chewing movements and catalepsy in male Sprague-Dawley rats over a 28-day treatment period compared with a vehicle (VEH) control group (n=12) (Karl et al., unpublished observation). Using two-dimensional gel electrophoresis (2DE), total protein extracts from the rat brain striatum were separated and protein expression was analyzed by Phoretix 2D Expression and Image Beta V4.02 software followed by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). 2DE gels resolved up to 450 protein spots, presumably different proteins and/or their isoforms. There were 30 protein spots showing statistically significant different densities between the RIS- and VEH-treated groups. All 30 proteins were successfully identified by MALDI-TOF MS, 28 of these were divided into groups based on their known functions. These included metabolic, signaling, transport, protein metabolism, chaperone, DNA binding and cell cycle categories. We conclude that chronic risperidone treatment accompanied by an EPS-like behavioral phenotype results in alterations in the striatal protein profile possibly subsequent to blockade of dopaminergic systems. These results suggest that possible mechanisms involved in APD-induced EPS include metabolic dysfunction and oxidative stress.

Risperidone in the treatment of psychotic depression

In the preset study, the authors investigated that effects of the antipsychotic drug risperidone on psychotic depression and examined the mechanism of risperidone to ameliorate psychotic depression. Fifteen patients met the DSM-IV criteria for major depressive disorder with psychotic features and the remaining five patients met those for bipolar I disorder (most recent episode depressed) with psychotic features (M/F: 8/12, age: 54+/-18). All patients were evaluated regarding their clinical improvement using the Hamilton Rating Scale for Depression (Ham-D), and Positive and Negative Syndrome Scale (PANSS). In addition, plasma concentrations of HVA and MHPG were analyzed by HPLC. Patients with a 50% or more improvement in Ham-D score were defined as responders. Three were prescribed risperidone alone, and the other 17 were administered risperidone as an addition to preexisting antidepressants or mood stabilizers. The preexisting antidepressants or mood stabilizers were as follows: paroxetine (6), lithium (3), valproic acid (3), clomipramine (2), fluvoxamine (1), amitriptyline (1), amoxapine (1). The average dose of risperidone was 1.8+/-0.5 mg/day. Eleven of twenty patients (55%) turned out to be responders 4 weeks after initiation of risperidone administration. No differences were observed between responders and nonresponders with respect to age, sex, Ham-D score before risperidone treatment, dose and plasma level of risperidone or its active metabolite, 9-hydroxyrisperidone. Plasma HVA levels before risperidone administration in responders were significantly higher than those in nonresponders. In addition, a significant correlation was observed between changes in plasma HVA level and the percentage improvement on Ham-D score. These results indicate that treatment with risperidone is effective to ameliorate psychotic depression, and the influence of risperidone on dopaminergic activity is associated with its efficacy.

Risperidone plasma levels, clinical response and side-effects

INTRODUCTION

Assessment of the relation between oral risperidone dose, serum drug levels and clinical response may provide important information for rational treatment decisions. Inter-individual differences in the liver cytochrome P450 system, especially in the CYP2D6 subsystem, which account for a significant portion of risperidone metabolism, may also influence plasma drug levels and alter clinical response parameters. We thus prospectively investigated risperidone serum concentrations in relation to clinical efficacy and side-effects and genotyped major CYP2D6 polymorphisms to determine their effect upon these parameters.

METHODS

Neuroleptic monotherapy with risperidone was administered to schizophrenia patients in a 6-week open dose clinical trial. Weekly assessments including CGI and PANSS ratings to assess psychopathology; SAS to assess medication side effects; and blood draws to quantify steady state plasma levels of risperidone and 9-OH-risperidone were carried out. In addition, major CYP2D6 polymorphisms including alleles *4, *6 and *14 were genotyped.

RESULTS

Eighty-two patients were recruited. Mean oral dose of risperidone was 4.3 +/- 0.9 mg. Mean plasma level of both risperidone and 9-OH-risperidone together ("active moiety") was 41.6 +/- 26.6 ng/ml. Significant improvements in PANSS scales and the various subscales ensued. There was a positive linear correlation between active moiety plasma levels and dose (r = 0.291, p = 0.015) and between risperidone and 9-OH-risperidone levels (r = 0.262; p = 0.016). Nonresponders to pharmacotherapy (PANSS-Improvement < 30%) showed significantly higher active moiety plasma levels (49.9 +/- 30.7 ng/ml) than responders (38.2 +/- 17.0 ng/ml; p = 0.045) without significantly higher oral doses (p = 0.601). Patients with longer illness duration (> or = 3 years) had significantly higher plasma drug levels than those with a shorter course (< 3 years; p = 0.039). Extrapyramidal side effects (EPS) and plasma levels were not correlated (r = 0.028; p = 0.843), but higher plasma levels at week 2 predicted an incidence for EPS (p < 0.050). Accordingly, patients initially receiving higher oral doses of risperidone were significantly more likely to respond with EPS in the trial course. Eight patients (9.8%) were heterozygous carriers of the CYP2D6 allele *4. CYP2D6 polymorphisms did not predict clinical response, but predicted a tendential increase in the plasma risperidone to 9-OH-risperidone ratio (0.5 +/- 0.6 vs. 1.9 +/- 1.8; p = 0.120).

DISCUSSION

The major finding was that responders to risperidone treatment had significantly lower blood levels of risperidone and 9-OH risperidone than patients who did not respond to the treatment despite administration of similar oral doses. The observed CYP2D6 polymorphisms did not contribute to altered clinical efficacy, but affected risperidone to 9-OH-risperidone ratios. Increased plasma levels of the active moiety in patients with longer illness may represent general aging effects. Conversely, the observed higher plasma levels in nonresponders may derive from unaccounted genetic metabolism abnormalities or Phase II metabolism disturbances. Patients initially receiving higher oral risperidone doses were more likely to respond with extrapyramidal side effects which reaffirms the need for careful titration. The high inter-individual variability in risperidone and 9-OH-risperidone metabolization and the relationship between clinical outcome and plasma levels warrants regular plasma level monitoring of both compounds to assess for the clinically relevant active moiety.

Influence of age and gender on risperidone plasma concentrations

There is limited information on gender- and age-specific effects on plasma concentrations of risperidone and its active metabolite, 9-hydroxyrisperidone. The present study investigated dose- and weight-adjusted plasma concentrations of risperidone and its metabolite in three age groups (45 years, 45-60 years, over 60 years). Gender-specific differences were examined in the whole sample and for the premenopausal subgroup. One hundred and twenty-nine patients (18-93 years) were included in the study, 52 (40%) male and 77 (60%) female. Concentrations of risperidone and 9-hydroxyrisperidone were measured at steady-state by high-performance liquid chromatography with electrochemical detection (HPLC-ED). When total plasma concentrations (risperidone plus 9-hydroxyrisperidone) were adjusted for daily maintenance dose (ng/mL/mg C/D ratio), significant differences between all age groups were found. We found a mean increase of the C/D ratio by 34.8% per decade in patients older than 42 years. No significant sex-related differences in the average plasma concentrations were observed for the whole sample and for the premenopausal subgroup. This study shows clear evidence of higher risperidone total plasma concentrations for patients over 40 years of age. This linear increase (over 30% per decade) may then lead to an increased incidence of adverse effects in elderly patients.

An open study of risperidone liquid in the acute phase of schizophrenia

An open-label study was performed to investigate the clinical efficacy and mechanisms of risperidone liquid in ameliorating positive symptoms in the acute phase of schizophrenia. Eighty-eight patients (M/F: 50/38; age: 18-74 years;, mean +/- SD =32 +/- 16 years) meeting DSM-IV criteria for schizophrenia and treated with risperidone liquid (14 patients also used lorazepam) were evaluated with regard to their clinical improvement and extrapyramidal side effects using the positive and negative syndrome scale (PANSS) and the Simpson and Angus scale (SAS), while plasma concentrations of HVA and MHPG were analysed by HPLC-ECD before and 4 weeks after risperidone liquid administration. Patients showing a 50% or greater improvement in PANSS scores were defined as responders. An improvement in the PANSS scores related to excitement, hostility and poor impulse control was seen within 7 days after administration of risperidone liquid, and an improvement with regard to hallucinatory behaviour and uncooperativeness was seen within 14 days after its administration. Finally, 68% of patients were classified as responders 4 weeks after risperidone liquid administration. The scores of SAS were not changed after risperidone liquid administration. Pretreatment plasma homovanillic acid (HVA) levels in the responders (8.1 +/- 2.9 ng/ml) were higher than those in nonresponders (5.9 +/- 1.9 ng/ml). In addition, a negative correlation was seen between the changes in plasma HVA levels and the percentage of improvement in PANSS scores. On the other hand, there were no differences between pretreatment plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) levels and those of nonresponders. These results suggest that risperidone liquid is effective and well tolerated for the treatment of acute phase schizophrenic patients, and that efficacy is related to its affects on dopaminergic activity, not noradrenergic activity.

Prediction of response to risperidone treatment with respect to plasma concencentrations of risperidone, catecholamine metabolites, and polymorphism of cytochrome P450 2D6

In the present study, we examined the relationships between plasma concentrations of risperidone and clinical responses, extrapyramidal symptoms, plasma levels of cotinine and caffeine, or cytochrome (cyp)2D6 genotypes. In addition, we also investigated the relationships between plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) or homovanillic (HVA) acid and clinical responses to risperidone. One hundred and 36 patients (male/female: 58/78, age 37+/-13 years) who met DSM-IV criteria for schizophrenia, schizoaffective disorder, delusional disorder and brief psychotic disorder, and who were being treated with risperidone alone, were evaluated regarding their clinical improvement and extrapyramidal symptoms using the Positive and Negative Syndrome Scale (PANSS) and Simpson and Angus (SAS), respectively, and plasma levels of cotinine, caffeine, MHPG and HVA were analysed by high-performance liquid chromatography. The cyp2D6*5 and *10 alleles were identified using the polymerase chain reaction. There was a positive correlation between plasma levels of risperidone plus 9-hydroxyrisperidone (active moiety) and SAS scores, but not the PANSS. Pretreatment HVA levels in responders were higher than those in nonresponders. In addition, there was a negative correlation between changes in HVA levels and improvement in PANSS scores. There was no association between plasma levels of risperidone and plasma levels of cotinine or caffeine. Furthermore, there were no differences in the risperidone/9-hydroxyrisperidone ratio, clinical improvements and extrapyramidal symptoms among cyp2D6 genotypes. These results indicate that pretreatment HVA levels and plasma concentrations of active moiety might play a part in predicting the clinical response and occurrence of extrapyramidal symptoms, respectively, when treating patients with risperidone.

Simultaneous determination of clozapine, olanzapine, risperidone and quetiapine in plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry

Clozapine (CLZ), olanzapine (OLZ), risperidone (RIP) and quetiapine (QTP) have been widely used in the treatment of schizophrenia. However, no study (or little study) has been conducted to determine the four drugs simultaneously by the use of high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-MS/ESI).

OBJECTIVE

To develop a sensitive method for simultaneous determination of CLZ, OLZ, RIP and QTP in human plasma by HPLC-MS/ESI.

METHODS

The analytes were extracted twice by ether after samples had been alkalinized. The HPLC separation of the analytes was performed on a MACHEREY-NAGEL C(18) (2.0 mm x 125 mm, 3 microm, Germany) column, using water (formic acid: 2.70 mmol/l, ammonium acetate: 10 mmol/l)-acetonitrile (53:47) as mobile phase, with a flow-rate of 0.16 ml/min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer and were detected in the selected ion recording (SIR) mode.

RESULTS

The calibration curves were linear in the ranges of 20-1000 ng/ml for CLZ and QTP, 1-50 ng/ml for OLZ and RIP, respectively. The average extraction recoveries for all the four analysts were at least above 80%. The methodology recoveries were higher than 91% for the analysts. The intra- and inter-day R.S.D. were less than 15%.

CONCLUSION

The method is accurate, sensitive and simple for routine therapeutic drug monitoring (TDM) and for the study of the pharmacokinetics of the four drugs.

Effects of various factors on steady-state plasma concentrations of risperidone and 9-hydroxyrisperidone: lack of impact of MDR-1 genotypes

AIMS

An in vitro study has suggested that risperidone is a substrate of P-glycoprotein, which is coded by MDR-1 gene. Thus, we studied the effects of major polymorphisms of the MDR-1 gene on plasma drug concentrations.

METHODS

Subjects were 85 schizophrenic patients receiving 3 mg twice daily of risperidone. Sample collections were conducted 12 h after the bedtime dosing. Plasma concentrations of risperidone and 9-hydroxyrisperidone were quantified using LC/MS/MS. MDR-1 genotypes (C3435T and G2677T/A) and CYP2D6 genotypes were identified using PCR-RFLP methods.

RESULTS

There was no difference in geometric mean (95% CI) of steady-state plasma concentration of risperidone between C3435T genotypes [C/C, C/T, T/T; 2.06 (1.63, 6.47), 2.96 (3.10, 7.91), 2.28 (1.81, 8.04) ng ml(-1), P = 0.759] or G2677T/A genotypes [G/G, G/T or A, T or A/T or A; 1.62 (0.08, 6.07), 2.64 (3.25, 7.10), 2.71 (2.77, 8.72) ng ml(-1), P = 0.625] or 9-hydroxyrisperidone between C3435T genotypes [38.3 (33.7, 50.1), 34.9 (32.9, 42.0), 35.7 (31.7, 42.3) ng ml(-1), P = 0.715] or G2677T/A genotypes [40.6 (33.0, 51.8), 35.0 (33.3, 42.4), 36.1 (32.8, 47.2) ng ml(-1), P = 0.601]. Multiple regression analyses including CYP2D6 genotypes, sex, and age revealed that steady-state plasma concentration of risperidone correlated with the number of mutated alleles for CYP2D6 (standardized partial correlation coefficients (beta) = 0.540, P < 0.001) and those of 9-hydroxyrisperidone (standardized beta = 0.244, P = 0.038) and active moiety (standardized beta = 0.257, P = 0.027) correlated with age.

CONCLUSIONS

These findings suggest that the MDR-1 variants are not associated with steady-state plasma concentration of risperidone or 9-hydroxyrisperidone, but CYP2D6 genotypes and age are determinants of these concentrations.

Correlation between scores on Continuous Performance Test and plasma concentration for schizophrenic patients on risperidone

The purpose of the present paper was to evaluate the relationship between plasma antipsychotics concentration and cognitive task performance. This may provide valuable information for rational dosage titration. Literature on the relationship between plasma risperidone (RIS) concentration and performance on the Continuous Performance Test (CPT) remains scarce. Ten patients (four male, six female) were given RIS for more than 1 year. Steady-state plasma concentrations of the parent drug RIS and its active metabolite, 9-hydroxy-risperidone (9-OH-RIS), were measured using specific liquid chromatography-tandem mass spectrometry assay. Psychopathology, side-effects of extrapyramidal symptoms (EPS) and CPT were also assessed. A negative correlation was found between CPT performance and the plasma RIS, 9-OH-RIS and its active moiety (RIS + 9-OH-RIS) concentrations. Both RIS and 9-OH-RIS have an impact on the CPT performance of schizophrenic patients. Optimal active moiety plasma concentration for best cognitive performance needs further study.

Analysis of eighteen antidepressants, four atypical antipsychotics and active metabolites in serum by liquid chromatography: a simple tool for therapeutic drug monitoring

Therapeutic drug monitoring necessitates efficient, fast and reliable analytical methods validated by external quality control. We therefore devised an isocratic reversed-phase HPLC method with ultraviolet detection and optimised this to quantify mirtazapine, reboxetine, moclobemide, venlafaxine, O-desmethylvenlafaxine, paroxetine, fluvoxamine, fluoxetine, norfluoxetine, sertraline, citalopram, amitriptyline, nortriptyline, imipramine, desipramine, doxepin, nordoxepin, clomipramine, norclomipramine, trimipramine, mianserine, maprotiline, normaprotiline, amisulpride, clozapine, norclozapine, quetiapine, risperidone and 9-OH-risperidone in human serum. After solid-phase extraction of the drugs and metabolites, the chromatographic separation was achieved on a Nucleosil 100-Protect 1 column with acetonitrile-potassium dihydrogenphosphate buffer as mobile phase. The method was validated for therapeutic and toxic serum ranges. A linear relationship (r>0.998) was obtained between the concentration and the detector signal. Recoveries were between 75 and 99% for the drugs and metabolites. The accuracy of the quality control samples, expressed as percent recovery, ranged from 91 to 118%; intra- and inter-assay-relative standard deviations were 0.9-10.2% and 0.9-9.7%, respectively. Additional external quality control is carried out since 3 years. This method is applicable to rapidly and effectively analyze serum or plasma samples for therapeutic drug monitoring of about 30 antidepressants and atypical antipsychotics.

Plasma levels of homovanillic acid and the response to risperidone in first episode untreated acute schizophrenia

We have previously reported that risperidone might improve negative symptoms in schizophrenia by influencing noradrenergic neurons. In the present study, we focused on the clinical efficacy and mechanisms of risperidone towards positive symptoms in the acute phase of schizophrenia. Thirty-four patients meeting DSM-IV criteria for schizophrenia and treated with risperidone alone were evaluated regarding their clinical improvement using the Positive and Negative Syndrome Scale (PANSS) before and 2 weeks after risperidone administration, and blood samples were also drawn at the same times. Plasma concentrations of homovanillic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol were analysed by high-performance liquid chromatography with electrochemical detection. Plasma HVA levels in the responders to the risperidone treatment (more than 50% improvement in scores of positive symptoms in PANSS) were higher than those of non-responders before risperidone administration. Furthermore, there was a negative trend between changes in plasma HVA levels and improvement of total scores for positive symptoms in PANSS. These results suggest that higher levels of plasma HVA before risperidone administration might be a predictor of a good response to risperidone treatment, and the influence of risperidone on dopaminergic activity might be associated with its efficacy in treating symptoms of schizophrenia in the acute phase.