Dutch Pharmacogenetics Working Group (DPWG) guideline for the gene-drug interaction between CYP2D6, CYP3A4 and CYP1A2 and antipsychotics

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate pharmacogenetics implementation in clinical practice by developing evidence-based guidelines to optimize pharmacotherapy. A guideline describing the gene-drug interaction between the genes CYP2D6, CYP3A4 and CYP1A2 and antipsychotics is presented here. The DPWG identified gene-drug interactions that require therapy adjustments when respective genotype is known for CYP2D6 with aripiprazole, brexpiprazole, haloperidol, pimozide, risperidone and zuclopenthixol, and for CYP3A4 with quetiapine. Evidence-based dose recommendations were obtained based on a systematic review of published literature. Reduction of the normal dose is recommended for aripiprazole, brexpiprazole, haloperidol, pimozide, risperidone and zuclopenthixol for CYP2D6-predicted PMs, and for pimozide and zuclopenthixol also for CYP2D6 IMs. For CYP2D6 UMs, a dose increase or an alternative drug is recommended for haloperidol and an alternative drug or titration of the dose for risperidone. In addition, in case of no or limited clinical effect, a dose increase is recommended for zuclopenthixol for CYP2D6 UMs. Even though evidence is limited, the DPWG recommends choosing an alternative drug to treat symptoms of depression or a dose reduction for other indications for quetiapine and CYP3A4 PMs. No therapy adjustments are recommended for the other CYP2D6 and CYP3A4 predicted phenotypes. In addition, no action is required for the gene-drug combinations CYP2D6 and clozapine, flupentixol, olanzapine or quetiapine and also not for CYP1A2 and clozapine or olanzapine. For identified gene-drug interactions requiring therapy adjustments, genotyping of CYP2D6 or CYP3A4 prior to treatment should not be considered for all patients, but on an individual patient basis only.

Effect of CYP2D6 pharmacogenetic phenotype and phenoconversion on serum concentrations of antidepressants and antipsychotics: a retrospective cohort study

BACKGROUND

Pharmacogenetics (PGx), especially in regard to CYP2D6, is gaining more importance in routine clinical settings. Including phenoconversion effects (PC) in result interpretation could maximize its potential benefits. However, studies on genetics of pharmacokinetic genes including the functional enzyme status are lacking.

AIM

The retrospective analyses of clinical routine data aimed to investigating how the CYP2D6 functional enzyme status affects serum concentrations and metabolite-to-parent ratios of seven common psychotropic drugs and allows an evaluation of the relevance of this information for patient care.

METHOD

Two patient cohorts (total n = 316; 44.2 ± 15.4 years) were investigated for the CYP2D6 functional enzyme status and its associations with drug exposure and metabolism of venlafaxine, amitriptyline, mirtazapine, sertraline, escitalopram, risperidone and quetiapine.

RESULTS

We found an increase in intermediate and poor metabolizers, as well as a decrease in normal metabolizers of CYP2D6 when including PC. Moreover, we found associations between amitriptyline exposure with the phenoconversion-corrected activity score of CYP2D6 (Spearman correlation; p = 0.03), and risperidone exposure with CYP2D6 functional enzyme status (Kruskal-Wallis test; p = 0.01), as well as between metabolite-to-parent ratio of venlafaxine and risperidone with CYP2D6 functional enzyme status (Kruskal-Wallis test; p < 0.001; p = 0.05).

CONCLUSION

The data stress the relevance of PC-informed PGx in psychopharmacological treatment and suggest that PC should be included in PGx result interpretation when PGx is implemented in routine clinical care, especially before initiating amitriptyline- or risperidone-treatment, to start with a dose adequate to the respective CYP2D6 functional enzyme status. Moreover, PGx and therapeutic drug monitoring should be used complementary but not alternatively.

Effects of CYP2D6, CYP3A5, and ABCB1 gene polymorphisms on the pharmacokinetics of two risperidone long-acting injection microsphere formulations

BACKGROUND

LY03004, a novel investigational risperidone long-acting injection (LAI) microsphere formulation, can release risperidone more quickly after injection than Risperdal Consta®. This study aimed to investigate the effects of genetic polymorphisms on the pharmacokinetics of LY03004 compared with those on Risperdal Consta®.

METHODS

A total of 100 Chinese patients with stable schizophrenia were randomly assigned to the LY03004 or Risperdal Consta® treatment group. Each patient received five biweekly intramuscular injections of 25 mg risperidone long-acting injection microspheres. A total of 34 blood samples before and after injections from Day 1 to Day 113 were collected from each patient, and polymorphic alleles of cytochrome P450 enzymes CYP2D6 (*4, *10, *14), CYP3A5 (*3), and ABCB1 (C1236 > T, G2677T/A, and C3435T) were analyzed using Sanger sequencing and polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

The risperidone C_max,ss, C_min,ss, AUC_0-tau,ss, and the ratio of risperidone to 9-hydroxyrisperidone (9-OH-R) in CYP2D6 intermediate metabolizers (IMs) were significantly different compared with those in normal metabolizers (NMs) in both the LY03004 and Risperdal Consta® groups (P < 0.05). However, 9-OH-R was not significantly different between IMs and NMs (P > 0.05). The AUC_0-tau,ss of the active moiety (risperidone plus 9-OH-R) was 6.51 ± 3.34 in NMs and 7.00 ± 1.81 in IMs (P = 0.071) in the LY03004 group and 6.07 ± 2.31 and 7.95 ± 3.42 (P = 0.053) in NMs and IMs, respectively, in the Risperdal Consta® group. In the LY03004 group, the C_max,ss of risperidone in carriers of the ABCB1-C3435T TT variant was significantly lower than that in CC and CT carriers (TT 7.76 ± 4.23 ng/mL, CT 11.6 ± 8.27 ng/mL, CC 14.3 ± 7.66 ng/ml; P = 0.045), but no significant differences were found in the active moiety. In the Risperdal Consta® group, C3435T TT carriers had significantly lower C_min,ss of the active moiety (TT 5.09 ± 4.38 ng/mL, CT 11.4 ± 8.42 ng/mL, CC 14.3 ± 6.43 ng/mL; P = 0.007). Furthermore, C_min,ss of the active moiety was significantly different among all ABCB1-G2677T/A genotypes (P < 0.05).

CONCLUSION

The pharmacokinetics of risperidone and the ratio of risperidone to 9-OH-R were highly dependent on CYP2D6 activity. However, there was no significant effect in 9-OH-R. A future study involving a larger sample is required to verify whether CYP2D6 IMs have lower risperidone active moiety clearance than CYP2D6 NMs for LAI formulations. In addition, the risperidone active moiety was eliminated faster in ABCB1-G2677T/A and C3435T TT carriers receiving Risperdal Consta®.

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

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

Determining the release kinetics of risperidone controlled release matrices to treat schizophrenia

Risperidone is an atypical antipsychotic agent clinically used to treat schizophrenia, bipolar diseases, and autism. Usually, the frequency of doses is twice daily. In the present study, risperidone controlled release matrices formulated using hydrophilic and hydrophobic polymers. The tablets were prepared by direct compression. The pre-compression and post-compression properties were assessed, along with swelling studies. The morphology of particles observed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The stability study on the drug was performed using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The optimized formulation was prepared with the help of hydrophilic polymer K100M (40% ratio). Furthermore, release kinetics had investigated. The release pattern of optimized formulation FT5 fitted best to zero-order kinetics and showed excellent release characteristics. The model-independent approach had been used, formulations FT6 and FT8 showed resemblance with FT5 in all three media, respectively. The once daily formulation of risperidone could be beneficial for schizophrenia patients and their caregivers and will improve patient compliance.

Anticholinergic Load and Nutritional Status in Older Individuals

OBJECTIVES

The association between anticholinergic load-based Anticholinergic Risk Scale scores and nutritional status is unclear in Japanese patients. The aim of this study was to establish whether anticholinergic load affects the nutritional status of geriatric patients in convalescent stages.

DESIGN

Retrospective longitudinal cohort study.

SETTING

Convalescent rehabilitation wards.

PARTICIPANTS

Of the 1490 patients aged ≥65 years who were discharged from convalescent rehabilitation wards between July 2010 and October 2018, 908 patients met the eligibility criteria. They were categorized according to the presence or absence of increased anticholinergic load from admission to discharge.

MEASUREMENTS

Demographic data, laboratory data, the Functional Independence Measure were analyzed between the groups. The primary outcome was Geriatric Nutritional Risk Index (GNRI) at discharge. Multiple linear regression analysis was performed to analyze the relationship between anticholinergic load and GNRI at discharge.

RESULTS

Multiple linear regression analysis after adjusting for confounding factors revealed that anticholinergic load was independently and negatively correlated with GNRI at discharge. Particularly, the use of chlorpromazine, hydroxyzine, haloperidol, metoclopramide, risperidone, etc. increased significantly from admission to discharge.

CONCLUSION

Increased anticholinergic load during hospitalization may be a predictor of nutritional status in geriatric patients.

Clinical Pharmacokinetics of a Lipid-Based Formulation of Risperidone, VAL401: Analysis of a Single Dose in an Open-Label Trial of Late-Stage Cancer Patients

BACKGROUND AND OBJECTIVES

A clinical trial was conducted to measure and analyse the pharmacokinetic parameters of a lipid formulation of risperidone, VAL401. The VAL401 formulation is designed to repurpose risperidone from an antipsychotic to an adenocarcinoma treatment, with the lipid formulation altering the cellular uptake of risperidone, thus enabling anticancer biology to be exhibited in preclinical testing.

METHODS

This first human trial of VAL401 measured the concentrations of risperidone and its primary metabolite, 9-hydroxyrisperidone, in the blood of patients after treatment with a single 2-mg dose of VAL401.

RESULTS

The trial provided information on differences in the pharmacokinetic profile of risperidone in VAL401 that may be caused by the formulation and/or the nature of the cancer patient population. VAL401 provided the following key pharmacokinetic parameters for the risperidone plasma concentration after a single 2-mg dose of VAL401, with results normalised to a dosage of 1 mg for comparison with literature values: Tmax, 2 h; Cmax, 8 ng/ml; half-life, 3.5 h; area under the plasma concentration-time curve from time zero to infinity (AUC0-∞), 58.2 ng h2/mL.

CONCLUSIONS

Further comparisons of the pharmacokinetic parameters of risperidone and 9-hydroxyrisperidone in plasma of patients administered VAL401 and the corresponding parameters obtained from published data for conventionally formulated risperidone provide evidence for altered biological processing of VAL401 as compared to risperidone. The absolute values obtained provide support for future studies of VAL401 as a cancer treatment, as the Cmax demonstrates sufficient exposure to reach the concentrations seen during preclinical anticancer testing, yet the overall exposure to the active moiety supports the use of the safety and tolerability data from conventional risperidone during future clinical trials.

Maintenance dose conversion between oral risperidone and paliperidone palmitate 1 month: Practical guidance based on pharmacokinetic simulations

AIM

We assessed the dosage strengths of paliperidone palmitate 1-month (PP1M) long-acting injectable resulting in similar steady-state (SS) exposures to the dosage strengths of oral risperidone using pharmacokinetic (PK) simulations.

METHODS

Population PK simulations of SS PK were performed using the PK models of oral risperidone and PP1M. The concentrations of active moiety (risperidone + paliperidone) from risperidone were compared to paliperidone concentrations resulting from PP1M administration. Similarity was assessed via graphical evaluation of median and 90% prediction intervals of SS PK profiles over 28 days.

RESULTS

Oral risperidone doses of 1, 2, 3, 4, and 6 mg/d are expected to result in similar SS PK as PP1M doses of 25, 50, 75, 100, and 150 mg eq. (which correspond to 39, 78, 117, 156, and 234 mg of paliperidone palmitate) respectively (ie 25-fold dose conversion factor from oral risperidone to PP1M).

CONCLUSIONS

This study provides clinicians with a practical guidance to establish suitable maintenance dose levels of PP1M and oral risperidone when transitioning patients from one formulation to another.

Pharmacokinetics of risperidone in different application forms - Comparing long-acting injectable and oral formulations

We aimed to explore the differences in the pharmacokinetics of risperidone between oral and long-acting injectable (LAI) formulations using a large database of therapeutic drug monitoring (TDM). Plasma concentrations of risperidone (RIS), its active metabolite (9-OH-RIS) and the active moiety (AM) (RIS+9-OH-RIS), their concentration-to-dose (C/D) ratios and ratio of RIS/9-OH-RIS (an index of CYP2D6 metabolic activity) were used to compare patients receiving risperidone orally (n = 851) and those treated with LAI RIS (n = 63). Patients taking CYP inducers or inhibitors or with liver/renal impairment were eliminated. Our study demonstrated that patients on LAI RIS, despite slightly higher RIS doses in the oral group, showed no significant differences in total AM or 9-OH-RIS. Conversely, RIS concentration, RIS C/D ratio and total C/D ratio were slightly higher in the LAI RIS group, reaching significance due to the large sample size. More importantly, the median ratio of RIS/9-OH-RIS was 0.52 in LAI RIS vs. 0.25 in the oral group, providing a significant difference (p < 0.001). After controlling for confounding factors, we replicated the RIS/9-OH-RIS ratio increases in patients with LAI RIS, probably reflecting a decrease in first-pass metabolism. More studies are required to establish the clinical use of TDM for patients on LAI RIS.

Response surface optimization, Ex vivo and In vivo investigation of nasal spanlastics for bioavailability enhancement and brain targeting of risperidone

Transnasal brain drug targeting could ensure better drug delivery to the brain through the olfactory pathway. Risperidone bioavailability is 66% in extensive metabolizers and 82% in slow metabolizers. The aim of this study is to investigate the ability of the nanovesicular spanlastics to effectively deliver risperidone through the nasal route to the brain and increase its bioavailability. Spanlastics formulae, composed of span and polyvinyl alcohol, were designed based on central composite statistical design. The planned formulae were prepared using ethanol injection method. The prepared formulae were characterized by testing their particle size, polydispersity index, zeta potential and encapsulation efficiency. The optimized formula having the lowest particle size, polydispersity index, the highest zeta potential and encapsulation efficiency was subjected to further investigations including characterization of its rheological properties, elasticity, transmission electron microscopy, in vitro diffusion, ex vivo permeation, histopathology and in vivo biodistribution. The optimized formula was composed of 5mg/mL span and 30mg/mL polyvinyl alcohol. It showed significantly higher transnasal permeation and better distribution to the brain, when compared to the used control regarding the brain targeting efficiency and the drug transport percentage (2.16 and 1.43 folds increase, respectively). The study introduced a successful and promising formula to directly and effectively carry the drug from nose to brain.

Clinical response in a risperidone-medicated naturalistic sample: patients' characteristics and dose-dependent pharmacokinetic patterns

The purpose of this study was to disentangle an association between plasma concentrations of risperidone (RIS), its active metabolite 9-hydroxyrisperidone (9-OH-RIS) and the active moiety, AM (RIS + 9-OH-RIS), and clinical response in a naturalistic sample. Plasma concentrations of RIS, 9-OH-RIS and AM in patients out of a therapeutic drug monitoring (TDM) database were compared between responders (n = 64) and non-responders (n = 526) using the Clinical Global Impressions (CGI) Scale. Daily dosage of risperidone did not differ between responders and non-responders. Differences for active moiety plasma levels between the two groups did not reach statistical significance. However, responders showed lower plasma concentrations of the parent compound RIS as well as lower metabolic ratios RIS/9-OH-RIS than non-responders (p = 0.017 and p = 0.034). These differences did not remain after controlling for age and baseline symptoms. Furthermore, the cohort was split into two subgroups based on the daily dosage: patients under high (≥6 mg/day) (R _H, n = 187) and patients under lower dosages (<6 mg) (R _L, n = 403) of risperidone. Differences between responders and non-responders after controlling for demographic and clinical characteristics remained only for plasma concentrations of active moiety in the lower-dose medicated groups; non-responders showed higher active moiety plasma concentrations than responders. Understanding the mechanisms involved and factors associated with the clinical response in patients medicated with antipsychotics is of great interest. Our data imply that clinical response to an antipsychotic treatment cannot be attributed to a single pharmacokinetic pattern. It seems to be rather a complex patchwork of influencing factors such as demographic and clinical characteristics as well as the metabolizer status as surrogate of CYP activity. It seems that the ratio between RIS and 9-OH-RIS may play a crucial role in mediating the clinical effect.

A Uniform Ultra-Small Microsphere/SAIB Hybrid Depot with Low Burst Release for Long-Term Continuous Drug Release

PURPOSE

In the present study, a uniform ultra-small microsphere/sucrose acetate isobutyrate (SAIB) hybrid depot (m-SAIB depot) was designed to provide a long-term sustained release drug delivery system which not only reduced the burst release of an SAIB depot, but also eliminated the lag-time of PLGA microspheres.

METHODS

Risperidone loaded m-SAIB depot (Ris-m-SAIB depot) was characterized by in vitro drug release, pharmacokinetics, in vivo degradation and biocompatibility, in comparison with risperidone loaded SAIB depot (Ris-SAIB depot).

RESULTS

Ris-m-SAIB depot showed a low burst release (0.64%) and a reduced in vitro drug release rate due to the encapsulation of most drug in microspheres. After intramuscular administration, the in vivo burst release of Ris-m-SAIB was significantly decreased, as reflected by the low Cmax/Cs(4-td) (approximately 30-fold reduction), in comparison with Ris-SAIB depot. From 4 to 78 days, Ris-m-SAIB depot showed a higher plasma drug level (1.55 ~ 16.30 ng/ml) with a steadier drug release profile compared with Ris-SAIB depot. Ris-m-SAIB depot degraded gradually with a degradation t1/2 of 54.6 days and exhibited good biocompatibility in vivo.

CONCLUSION

These results demonstrate the potential application of a uniform ultra-small microsphere/SAIB hybrid depot for continuously delivering small drug molecules for long periods of time without burst release.

Liver enzyme abnormalities during antipsychotic treatment: a case report of risperidone-associated hepatotoxicity

BACKGROUND

Drug-induced liver enzyme abnormalities may indicate hepatic injury. Antipsychotic drugs also may cause increase in the liver enzymes and serum bilirubin levels. The present report evaluates the case of a patient with risperidone-associated hepatocellular damage.

CASE SUMMARY

A 19-year-old Caucasian man was admitted to the Department of Psychiatry with paranoid schizophrenia and risperidone was administered in a gradually increasing dose up to 8 mg/day. After 3 weeks of treatment, he experienced asthenia and weight loss. The level of aspartate aminotransferase was 283 IU/L (normal: <30 IU/L), and the alanine aminotransferase level was 778 IU/L (normal: <36 IU/L). Treatment with risperidone was immediately discontinued. Six days after drug withdrawal, the alanine aminotransferase level fell more than 50%, and a complete return to normalcy was seen within 2 months.

RESULTS

In the present case, a possible causal association between risperidone and hepatocellular damage has been observed due to the temporal relationship between the administration of the drug and the onset of hepatic abnormalities, and a following rapid recovery after stopping the drug. As the hepatic damage could be related to the plasma concentration of risperidone which is highly influenced by the hepatic enzyme CYP2D6, the patient was genotyped for CYP2D6. He was classified as homozygous wild type for CYP2D6.

CONCLUSIONS

The risk for developing hepatotoxicity during risperidone therapy cannot be supported by the patient CYP2D6 genotype. In clinical practice, it may be recommended to obtain baseline liver function tests before starting risperidone and regular screening for liver enzyme changes during therapy.

Risperidone dosing in children and adolescents with autistic disorder: a double-blind, placebo-controlled study

Efficacy and safety of 2 risperidone doses were evaluated in children and adolescents with autism. Patients (N = 96; 5-17 years), received risperidone (low-dose: 0.125 mg/day [20 to <45 kg], 0.175 mg/day [>45 kg] or high-dose: 1.25 mg/day [20 to <45 kg], 1.75 mg/day [>45 kg]) or placebo. Mean baseline (range 27-29) to endpoint change in Aberrant Behavior Checklist-Irritability (primary endpoint) was significantly greater in the high-dose-(-12.4 [6.5]; p < 0.001), but not low-dose (-7.4 [8.1]; p = 0.164) group, versus placebo (-3.5 [10.7]). Clinical Global Impressions-Severity and Children's Yale-Brown Obsessive Compulsive Scale scores improved significantly only in the high-dose group, consistent with ABC-I results. Somnolence, sedation and increased appetite occurred more frequently in high-versus low-dose groups. Overall, increased appetite occurred most frequently.

Selegiline Transdermal System: An Examination of the Potential for CYP450-Dependent Pharmacokinetic Interactions With 3 Psychotropic Medications

Selegiline transdermal system (STS) is a recently approved monoamine oxidase inhibitor antidepressant. This article reports results from 3 studies examining the potential for cytochrome P450-dependent pharmacokinetic interactions between STS and 3 psychotropic medications that might be coadministered. Three open-label, randomized, Latin square, 3-sequence crossover design studies were conducted with healthy volunteers to determine the pharmacokinetic parameters of STS 6 mg/24 h and test drug (alprazolam, olanzapine, or risperidone) when administered alone and concomitantly. All pharmacokinetic parameters of interest were unaltered following selegiline or test drug monotherapy when compared to concomitant therapy. This was confirmed by least squares mean ratios and their 90% confidence intervals of log(e)-transformed C(max) and AUC(tau) values, using either standard bioequivalence criteria of 80% to 125% or study-defined 70% to 143% boundary criteria. These results demonstrate that STS 6 mg/24 h may provide an antidepressant option that is unlikely to result in CYP450-mediated pharmacokinetic drug-drug interactions.

Assessment of adverse effects of neurotropic drugs in monkeys with the "drug effects on the nervous system" (DENS) scale

Research into therapeutics for neuropsychiatric disorders is increasingly focusing on drugs with new mechanisms of action, and such agents are often assessed in preclinical studies using nonhuman primates. However, researchers lack a standardised method to compare different drugs for common adverse effects on the nervous system. We have developed a new scale for this purpose, named "Drug Effects on the Nervous System" (DENS), and tested its utility in an analysis of the second-generation antipsychotic risperidone in monkeys. The behavioural effects of risperidone over a ten-fold clinically relevant exposure range were rated with the DENS scale and compared with a standard motor disability scale for primates. The ratings were correlated with projected D2 and 5-HT2A receptor occupancies over time. The DENS scale detected dose-dependent side effects of risperidone in addition to the motor effects detected with the motor disability scale, including cognitive, sensorimotor and autonomic functions. A consistent temporal association between the DENS scale changes and the projected D2 receptor occupancy was observed, and the DENS scale ratings demonstrated high inter-rater reliability. These results demonstrate the usefulness of the DENS scale as a highly sensitive, reliable and accurate method to identify common adverse effects of risperidone and potentially other neurotropics for translational studies in primates.

Impact of olanzapine or risperidone treatment on insulin sensitivity in schizophrenia or schizoaffective disorder

AIM

To assess changes in insulin sensitivity in non-diabetic adults with schizophrenia or schizoaffective disorder treated with olanzapine or risperidone.

METHODS

One hundred and thirty patients were randomly assigned to 12 weeks double-blind treatment with olanzapine or risperidone. Insulin sensitivity was measured using a two-step euglycaemic, hyperinsulinaemic clamp procedure. Whole-body adiposity was measured using dual-energy X-ray absorptiometry. The primary endpoint was the within-group change from baseline in insulin sensitivity normalized to fat-free mass (M(ffm) /I) during the clamp procedure's low-insulin phase, using an analysis of covariance model including the covariate weight change.

RESULTS

Forty-one olanzapine-treated and 33 risperidone-treated patients completed baseline and endpoint clamp measurements. Mean M(ffm) /I during the low-insulin phase declined 9.0% (p = 0.226) in olanzapine-treated patients and 13.2% (p = 0.047) in risperidone-treated patients (between-group difference p = 0.354). During the high-insulin phase, M(ffm) /I declined 10.4% (p = 0.036) in olanzapine-treated patients and 2.1% (p = 0.698) in risperidone-treated patients (between-group difference p = 0.664). Changes in M(ffm) /I correlated inversely with changes in body weight and adiposity, which were generally higher in olanzapine-treated patients. Significant within-group increases in fasting glucose, but not haemoglobin A1c (HbA1c), were observed during olanzapine treatment. The fasting glucose change was not correlated with M(ffm) /I changes.

CONCLUSIONS

Small, but statistically significant, decrements in insulin sensitivity were observed in olanzapine- and risperidone-treated patients at 1 of 2 insulin doses tested. Significant increases in fasting glucose and insulin and total fat mass were observed only in olanzapine-treated patients. Changes in insulin sensitivity correlated significantly with changes in weight or adiposity, but not with changes in glucose.

Development of controlled-release matrix tablet of risperidone: influence of Methocel®- and Ethocel®-based novel polymeric blend on in vitro drug release and bioavailability

Controlled-release (CR) matrix tablet of 4 mg risperidone was developed using flow bound dry granulation-slugging method to improve its safety profile and compliance. Model formulations F1, F2, and F3, consisting of distinct blends of Methocel® K100 LV-CR and Ethocel® standard 7FP premium, were slugged. Each batch of granules (250-1,000 μm), obtained by crushing the slugs, was divided into three portions after lubrication and then compressed to 9-, 12-, and 15-kg hard tablets. In vitro drug release studies were carried out in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 6.8) using a paddle dissolution apparatus run at 50 rpm. The CR test tablet, containing 30% Methocel® and 60% Ethocel® (F3) with 12-kg hardness, exhibited pH-independent zero-order release kinetics for 24 h. The drug release rate was inversely proportional to the content of Ethocel®, while the gel layer formed of Methocel® helped in maintaining the integrity of the matrix. Changes in the hardness of tablet did not affect the release kinetics. The tablets were reproducible and stable for 6 months at 40 ± 2°C/75 ± 5% relative humidity. Risperidone and its active metabolite, 9-hydroxyrisperidone, present in the pooled rabbit's serum, were analyzed with HPLC-UV at λ(max) 280 nm. The CR test tablet exhibited bioequivalence to reference conventional tablet in addition to the significantly (p < 0.05) optimized peak concentration, C(max), and extended peak time, T (max), of the active moiety. There was a good association between drug absorption in vivo and drug release in vitro (R(2) = 0.7293). The successfully developed CR test tablet may be used for better therapeutic outcomes of risperidone.

[Case of schizophrenia in which depressive and negative symptoms relapsed on switching from oral risperidone to risperidone long-acting injection]

I report a case of schizophrenia in which depressive and negative symptoms relapsed on switching from oral risperidone to risperidone long-acting injection (RLAI). The patient, with a 31-year history of schizophrenia, did not fully understand his disease. Therefore, adherence to medication had been extremely poor. The discontinuation of medication led to the recurrence of the disease. After hospital treatment, he was discharged to a group home. From then, the disease had been kept in remission by risperidone at 4 mg/day, and RLAI was introduced for the purpose of further social reintegration and QOL improvement. After starting RLAI at 25 mg, however, a stiff expression and irritability appeared. Therefore, RLAI was increased up to 50 mg, but depressive and negative symptoms relapsed. Subsequently, RLAI was discontinued and oral risperidone was re-administered, and the above mental symptoms improved in a relatively rapid manner. The difference in the ratio of plasma and brain concentrations between each active moiety, risperidone and 9-OH risperidone (paliperidone), resulting from the difference in administration routes, was suggested to be involved as the main factor. In this case, it is likely that positive symptoms did not relapse because plasma concentrations of the active moiety itself were well maintained by introducing RLAI. However, depressive and negative symptoms relapsed possibly as a result of reduced affinity for the alpha2A receptor with relatively decreased plasma concentrations of 9-OH risperidone when compared to oral administration. Another possibility is that negative symptoms were secondary induced by excess administration of antipsychotics, but there has been no such report on RLAI so far. For the reason noted above, careful follow-up is considered necessary when switching from oral risperidone to RLAI because mental symptoms might get worse.

[Advances in the study of polymeric micelles used in oral administration]

Polymeric micelles which are self-assembled from amphiphilic copolymers are thermodynamically stable, and they can solubilize hydrophobic drugs by the hydrophilic core. Many excellent active compounds are confined because of general low oral bioavailability due to poor solubility. Take into account from the two points above, polymeric micelles may be used as proper oral carrier to improve the dissolubility of hydrophobic drugs, and enhance the permeation though gastrointestinal tract, therefore, the pharmacodynamics is elevated. Meanwhile, the segments in copolymers are multivariate, so many kinds of micelles can be obtained, such as, pH- or thermo- sensitive as well as mucoadhesive ones. The modified micelles can alter drug release profiles while solubilizing them, that is why the oral bioavailability increase further. In this review, recent progress of polymeric micelles used in oral administration is summarized, and the prospect of polymeric micelles' application in this field is also evaluated.

Effect of CYP2D6, CYP3A5, and MDR1 genetic polymorphisms on the pharmacokinetics of risperidone and its active moiety

Clinical studies suggest that plasma levels of risperidone and its active moiety (risperidone + 9-hydroxyrisperidone) correlate with adverse drug effects. The aim of this study is to evaluate the pharmacogenetic variability in the disposition of risperidone and the active moiety in healthy Chinese subjects. A 2-mg single dose of risperidone is orally administered to 23 healthy Chinese subjects. The risperidone and 9-hydroxyrisperidone serum concentrations are measured. The polymorphic alleles of CYP2D6*10, CYP3A5*3, MDR1 C1236T, G2677T/A, and C3435T are determined in each subject. The mean maximum plasma concentration and area under the time-concentration curve extrapolated to infinity for risperidone are significantly higher in subjects possessing the CYP2D6*10 allele than in those with the CYP2D6*1/*1 and *1/*10 genotype. For active moiety, the subjects who carry both homozygous CYP2D6*10 and homozygous CYP3A5*3 have 98% higher area under the time-concentration curve extrapolated to infinity and 59% higher maximum plasma concentration compared with other CYP2D6 EM subjects. The MDR1 2677GA genotype may also play a role in risperidone pharmacokinetics. Further studies are needed to explore the impact of MDR1 2677GA and CYP3A5 polymorphisms on risperidone therapy.

[Paliperidone--a novel second-generation antipsychotic]

Paliperidone Depot (PAL ER) is a new second-generation antipsychotic with pharmacodynamics resembling those of risperidone. PAL ER is slowly and smoothly released in 24 hours. Its half-life is about 24 hours. PAL is primarily eliminated unchanged in urine. Three short-term studies and one relapse study found PAL ER to be significantly more effective than placebo in all doses (3-15 mg once a day). There are no head-to-head comparisons with other antipsychotics, including risperidone. On the existing evidence it is not possible to ascertain whether PAL ER is better than risperidone in terms of effects and tolerability.

Olanzapine orally disintegrating tablet vs. risperidone oral solution in the treatment of acutely agitated psychotic patients

OBJECTIVE

Efficacy and tolerability of risperidone oral solution (RIS-OS) and olanzapine orally disintegrating tablet (OLZ-ODT) were compared for the treatment of acute psychotic agitation.

METHOD

During a 2-month period, patients scoring > or =15 on the Excited Component for Positive and Negative Syndrome Scale (PANSS-EC) were assigned to treatment with OLZ-ODT (n=34) or RIS-OS (n=53) on psychiatric emergency situations, and assessed every 15 min.

RESULTS

Two (OLZ-ODT and RIS-OS) by five (0-, 15-, 30-, 45- and 60-min time points) repeated-measures analysis of variance revealed only a significant main effect of time course on PANSS-EC (F=82.2, P<.0001). No differences in the number of patients receiving additional injection due to worsening were found (OLZ-ODT, 11.8%; RIS-OS, 9.4%). No differences in rate of extrapyramidal symptoms and patient satisfaction with assigned treatment were found. However, patients in the OLZ-ODT group recovered significantly more from tachycardia than those in the RIS-OS group (t=2.17, P=.03).

CONCLUSION

OLZ-ODT and RIS-OS treatments yielded similar improvements in acutely agitated patients who accepted oral medication. However, on one physiological parameter (i.e., tachycardia) OLZ-ODT might be superior to RIS-OS. Physiological indicators may also be useful for measuring levels of agitation.

Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice

Efflux transporters, like P-glycoprotein (P-gp), may limit the access of drugs to the brain via the blood-brain barrier. The antipsychotic drug risperidone and its active metabolite 9-hydroxyrisperidone (paliperidone) are substrates of P-gp. Motor behavior of P-gp deficient mice (mdr1a/1b (-/-, -/-)) and wild type animals on a rotarod after acute doses of risperidone or haloperidol, a nonsubstrate of P-gp, were analysed aiming to show that P-gp substrate properties of an antipsychotic drug have functional consequences. Behavioral tests revealed dose-dependent effects of 0.3-3 mg/kg risperidone in wild type animals 0.5-12 h after i.p. injection of the drug. In knockout mice the 0.3 mg/kg dose of risperidone was as effective as the 3 mg/kg dose in wild type mice. A dose of 0.3 mg/kg haloperidol, however, exhibited similar pharmacodynamic effects in both genotypes. Brain concentrations of risperidone plus 9-hydroxyrisperidone were 10-fold higher in knockout than in wild type animals whereas brain concentrations of haloperidol did not differ between the two genotypes. P-gp-dependent brain distribution kinetics and behavioral effects of risperidone give evidence that the expression of P-gp has an impact on psychotropic drug actions when treating patients with drugs that are substrates of P-gp.

In vivo evaluation of risperidone-SAIB in situ system as a sustained release delivery system in rats

The objective of this study was to evaluate a sustained release sucrose acetate isobutyrate (SAIB) in situ system formulation of risperidone (RSP) in vivo. The formulation contained SAIB, ethanol, and polylactic acid (PLA) as a release regulator. In vivo pharmacokinetics (PK) studies have shown that PLA is effective in reducing the burst effect. After a 12.5mg/kg IM injection of a 25mg/g RSP-SAIB in situ system, the C(max) was markedly reduced from 944.1+/-80.2 to 330.4+/-33.6ng/ml by increasing PLA from 1% to 10% (w/w), the T(max) were prolonged from 2 to 4.3+/-2.0h, and the area under the curve from day 0 to 2 (AUC(0-2day)) was reduced significantly from 16294.8+/-3946.4 to 7025.3+/-1979.2ngh/ml. For the RSP-SAIB in situ system including 10% PLA, the high release rates over a short period allowed therapeutic plasma concentrations to be achieved in the initial stages after activation, and sustained release of the drug led to a stable plasma concentration (by day 25, the plasma concentration was 8% of the C(max)). These initial in vivo studies suggest that RSP-SAIB in situ system is effective as a sustained delivery system.

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.

In vitro and in vivo demonstration of risperidone implants in mice

BACKGROUND

Non-adherence with medication is a critical limitation in current long-term treatment of schizophrenia and a primary factor in poor quality-of-life outcomes. However, few treatments have addressed this shortcoming using an implantable drug delivery approach. The goal of this study was to provide in vitro and in vivo proof of concept for a long-term implantable risperidone delivery system in mice.

METHODS

Implantable formulations of risperidone were created using the biodegradable polymer Poly Lactic co Glycolic Acid (PLGA) combined with various drug loads. Implant bioactivity was tested using in vitro release and stability studies, as well as in vivo pharmacokinetic and behavioral studies in mice.

RESULTS

The pattern of risperidone release is influenced by various parameters, including polymer composition and drug load. In vitro measures demonstrate that risperidone is stable in implants under physiological conditions. Behavioral measures demonstrate the bioactivity of risperidone implants delivering 3 mg/kg/day in mice, while pharmacokinetic analyses indicate that reversibility is maintained throughout the delivery interval.

CONCLUSIONS

The current report suggests that implantable formulations are a viable approach to providing long-term delivery of antipsychotic medications based on in vivo animal studies and pharmacokinetics. Implantable medications demonstrated here can last two months or longer while maintaining coherence and removability past full release, suggesting a potential paradigm shift in the long-term treatment of schizophrenia.

Sensitive liquid chromatography/tandem mass spectrometry method for the simultaneous determination of olanzapine, risperidone, 9-hydroxyrisperidone, clozapine, haloperidol and ziprasidone in rat brain tissue

One prerequisite for therapeutic effects of psychiatric drugs is the ability to pass the blood brain barrier. Hence, it is important to know the concentration of antipsychotic drugs in brain tissue. In general, determinations of lipophilic compounds from lipophilic matricies such as the brain are a challenge. Here we have adapted a plasma assay for antipsychotics for the target organ the brain. Using modified sample preparation and chromatographic strategies, the analytes were extracted from rat brain homogenate and analyzed by LC-MS/MS. The method used a Waters Atlantis dC-18 (30 mm x 2.1 mm i.d., 3 microm) column with a mobile phase of acetonitrile/5 mM ammonium formate (pH 6.1 adjusted with formic acid) and gradient elution. All analytes were detected in positive ion mode using multiple-reaction monitoring. The method was validated and the linearity, lower limit of quantitation, precision, accuracy, recoveries, specificity and stability were determined. This method was then successfully used to quantify the rat brain tissue concentration of the analytes after chronic treatment with these antipsychotic drugs.

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.

A study of genetic (CYP2D6 and ABCB1) and environmental (drug inhibitors and inducers) variables that may influence plasma risperidone levels

Risperidone (R) is metabolized to 9-hydroxyrisperidone (9-OHR) by cytochrome P450 2D6 (CYP2D6). The main objective of this naturalistic study was to investigate the variables associated with two plasma ratios: the plasma R:9-OHR concentration ratio and the total concentration-to-dose (C:D) ratio. These ratios were studied as continuous measures by linear regression analyses and as three dichotomous variables in logistic regression analyses: R:9-OHR ratio >1 (indicative of lack of CYP2D6 activity), C:D ratio >14 (indicative of diminished R elimination), and C:D ratio <3.5 (indicative of increased R elimination). Plasma R levels; genotypes for CYP2D6, CYP3A5; and ABCB1 genes, and co-medication, including CYP inhibitors and CYP3A inducers, were studied in 277 patients. Almost all CYP2D6 poor metabolizers (PMs) had an inverted R:9-OHR ratio (>1). Having a CYP2D6 PM phenotype was strongly associated with a C:D ratio >14 (OR=8.2; 95% confidence interval [CI]=2.0-32.7), indicating diminished R elimination. CYP2D6 ultrarapid metabolizers (UMs) did not exhibit an increased R elimination. Some ABCB1 (or MDR1) variants were significantly associated with increased R:9-OHR ratios and decreased C:D ratios, but the results were neither consistent nor robust. Taking CYP inhibitors was significantly associated with a C:D ratio >14 (OR=3.8; CI=1.7-8.7) and with an inverted R:9-OHR ratio. Taking CYP3A inducers was significantly associated with a C:D ratio <3.5 (OR=41.8; CI=12.7-138), indicating increased R elimination. Female gender and old age appeared to be associated with a lower R elimination. Our study indicated that the CYP2D6 PM phenotype may have a major role in personalizing R doses, whereas the CYP3A5 PM phenotype probably has no role. CYP inducers and inhibitors appear to be relevant to R dosing. New studies are needed, particularly to further assess the role of the CYP2D6 UM phenotype and ABCB1 variants in R pharmacokinetics.

Equivalent switching dose from oral risperidone to risperidone long-acting injection: a 48-week randomized, prospective, single-blind pharmacokinetic study

OBJECTIVE

Previous studies showed clinical benefit of risperidone long-acting injection in the treatment of schizophrenia. However, the equivalent switching dose from oral risperidone to risperidone long-acting injection was still in debate. This study, conducted among hospitalized patients, included a long-enough study period and optimal control of drug compliance to test the equivalent switching dose.

METHOD

Fifty symptomatic, stable hospitalized patients with DSM-IV schizophrenia were randomly assigned to receive either daily oral risperidone or risperi-done long-acting injection every 2 weeks. Those originally receiving an oral risperidone dose of 4 mg/day or less received 25 mg of risperidone long-acting injection, those taking an oral dose of more than 4 mg/day but of 6 mg/day or less received 37.5 mg of risperidone long-acting injection, and those taking more than 6 mg/day received 50 mg of risperidone long-acting injection. Assessments of clinical efficacy, side effects, metabolic safety, drug tolerance, and serum concentration of risperi-done metabolites were performed repeatedly. The study was conducted from March 2004 to May 2005.

RESULT

Forty-five patients (90%) completed the study. There were no significant differences in Positive and Negative Syndrome Scale (PANSS) scores between the 2 groups, but the risperidone long-acting injection group showed reduced UKU Side Effect Rating Scale total scores (p = .048), Simpson-Angus Scale scores (p = .028), prolactin levels (p = .046), and serum concentrations of risperidone metabolites (p = .028). Among the risperidone long-acting injection group, patients who received either 25 mg q 2 weeks or 37.5 mg q 2 weeks of risperidone long-acting injection showed increased PANSS scores (p = .058), decreased serum metabolite concentrations (p = .028), and an increased tendency to relapse.

CONCLUSIONS

The results support good tolerability of risperidone long-acting injection, but it is suggested that the equivalent switching dose be adjusted as follows: those originally on an oral risperidone dose of 3 mg/day or less should receive 25 mg of risperidone long-acting injection, those taking an oral dose of more than 3 mg/day but of 5 mg/day or less should receive 37.5 mg, and those taking an oral dose of more than 5 mg/day should receive 50 mg of risperidone long-acting injection.

Atypical antipsychotic administration during late pregnancy: placental passage and obstetrical outcomes

OBJECTIVES

There are limited data regarding the use of atypical antipsychotic medications in pregnancy. The objectives of the current study were to quantify placental permeability to antipsychotic medications and to document obstetrical outcomes for women taking these agents proximate to delivery.

METHOD

The authors conducted a prospective observational study of women treated with an atypical antipsychotic or haloperidol during pregnancy. Maternal and umbilical cord plasma samples collected at delivery were analyzed for medication concentrations. Placental passage was defined as the ratio of umbilical cord to maternal plasma concentrations (ng/ml). Obstetrical outcome was ascertained through maternal reports and reviews of obstetrical records.

RESULTS

Fifty-four pregnant women with laboratory-confirmed antipsychotic use proximate to delivery were included in the analysis. Complete maternal-infant sample pairs were available for 50 participants. Placental passage ratio was highest for olanzapine (mean=72.1%, SD=42.0%), followed by haloperidol (mean=65.5%, SD=40.3%), risperidone (mean=49.2%, SD=33.9%), and quetiapine (mean=23.8%, SD=11.0%). There were tendencies toward higher rates of low birth weight (30.8%) and neonatal intensive care unit admission (30.8%) among neonates exposed to olanzapine.

CONCLUSIONS

All four antipsychotics demonstrated incomplete placental passage. Quetiapine demonstrated the lowest placental passage of the medications studied. These novel data provide an initial quantification of the placental passage of antipsychotics and fetal exposure in humans, demonstrating significant differences between individual medications.

Rifampin, a cytochrome P450 3A inducer, decreases plasma concentrations of antipsychotic risperidone in healthy volunteers

BACKGROUND

Although cytochrome P450 (CYP) 2D6 is often thought to be the only CYP responsible for the metabolism of risperidone, many reports suggest that CYP3A may be involved too. Rifampin, a potent CYP3A inducer, has been known to markedly decrease plasma concentrations of various drugs, which are concomitantly administered during treatment.

OBJECTIVE

To examine the effect of rifampin on plasma concentrations of a single oral dose of risperidone in healthy Thai male volunteers.

METHODS

In an open, randomized two-phase crossover study, separated by a 2-week period, 10 healthy Thai male volunteers received a single oral dose of 4-mg risperidone alone or with 600 mg rifampin, orally once daily for 5 days. Serial blood samples were collected at specific time points for a 48-h period. Risperidone was measured in plasma using high performance liquid chromatography with ultraviolet detection. Pharmacokinetic parameters were determined by using non-compartmental analysis.

RESULTS

Co-administration with 600-mg rifampin once daily for 5 days was associated with a significant decrease in risperidone area under the curve (AUC(0-48)) and maximal concentration (C(max)) by 72% (157 x 49 +/- 48 x 80 vs. 42 x 66 +/- 7 x 81 ng/L/h; P<0 x 01) and 50% (32 x 44 +/- 6 x 05 vs. 16 x 16 +/- 2 x 73 ng/mL; P<0 x 05), respectively when compared with risperidone alone.

CONCLUSIONS

Rifampin when used concurrently with risperidone significantly decreases the plasma concentration of risperidone. Our results provide in vivo evidence of the involvement of CYP3A in the metabolism of risperidone, in addition to CYP2D6. Thus, co-administration of risperidone with CYP3A inducer(s), including rifampin should be recognized or avoided in clinical practice.

Association of the RGS2 gene with extrapyramidal symptoms induced by treatment with antipsychotic medication

OBJECTIVES

To investigate the role of genes encoding regulators of G protein signaling in early therapeutic response to antipsychotic drugs and in susceptibility to drug-induced extrapyramidal symptoms. As regulators of G protein signaling and regulators of G protein signaling-like proteins play a pivotal role in dopamine receptor signaling, genetically based, functional variation could contribute to interindividual variability in therapeutic and adverse effects.

METHODS

Consecutively hospitalized, psychotic patients with Diagnostic and Statistical Manual of Mental Disorder-IV schizophrenia (n=121) were included in the study if they received treatment with typical antipsychotic medication (n=72) or typical antipsychotic drugs and risperidone (n=49) for at least 2 weeks. Clinical state and adverse effects were rated at baseline and after 2 weeks. Twenty-four single nucleotide polymorphisms were genotyped in five regulators of G protein signaling genes.

RESULTS

None of the single nucleotide polymorphisms were related to clinical response to antipsychotic treatment at 2 weeks. Five out of six single nucleotide polymorphisms within or flanking the RGS2 gene were nominally associated with development or worsening of parkinsonian symptoms (PARK+) as measured by the Simpson Angus Scale, one of them after correction for multiple testing (rs4606, P=0.002). A GCCTG haplotype encompassing tagging single nucleotide polymorphisms within and flanking RGS2 was significantly overrepresented among PARK+ compared with PARK--patients (0.23 vs. 0.08, P=0.003). A second, 'protective', GTGCA haplotype was significantly overrepresented in PARK--patients (0.13 vs. 0.30, P=0.009). Both haplotype associations survive correction for multiple testing.

CONCLUSIONS

Subject to replication, these findings suggest that genetic variation in the RGS2 gene is associated with susceptibility to extrapyramidal symptoms induced by antipsychotic drugs.

Evaluation of a treatment manual for risperidone long-acting injectable

We evaluated the usefulness of a treatment manual to facilitate the use of long-acting injectable risperidone in community mental health centers (CMHCs) during an open-label observational study. Perceived clinical utility and clinician adherence to the manual were evaluated. Patient adherence to treatment satisfaction, Clinical Global Impression of Severity (CGI-S) and the Schizophrenia Quality-of-Life Scale (SQLS) were assessed. Mean score for overall utility of the guidebook was 4.2 +/- .6 (scale ratings ranged from 1 = not at all to 5 = extremely). Most clinicians (89-100%) found the guidebook useful, and were adherent to key aspects of appropriate treatment use including concomitant oral risperidone use and injection and dosing parameters for long-acting risperidone. Most patients were adherent to treatment (86.7%), preferred long-acting risperidone over oral risperidone (72.6%) or other oral antipsychotics (78.4%) and were satisfied with long-acting risperidone (90.1%). The open-label observational design limits interpretation of these data. However, in this study manual-supported use of long-acting risperidone was associated with successful implementation of this pharmacologic treatment in the CMHC setting.

[Development and identifiability analysis of parent-metabolite pharmacokinetic model for risperidone and its main active metabolite 9-hydroxyrisperidone]

To develop a parent-metabolite pharmacokinetic model for risperidone (RIP) and its major active metabolite (9-hydroxyrisperidone) and investigate their pharmacokinetics characteristics in healthy male volunteers, twenty-two healthy volunteers were orally given a single dose of 2 mg RIP. Plasma samples were collected in the period of 96 hours and concentrations of RIP and 9-hydroxyrisperidone were measured by a validated HPLC/MS method. CYP2D6 phenotypes were identified by the T1/2 of RIP and 9-hydroxyrisperidone according to the literature. Model structure identifiability analysis was performed by the similarity transformation approach to investigate whether the unknown parameters of the proposed model could be estimated from the designed experiment. Pharmacokinetics parameters were estimated using weighted least squares method, and the final pharmacokinetics model were tested and evaluated by Monte Carlo simulation. Eighteen volunteers were phenotyped as extensive metabolizers (EM) and four volunteers were identified as intermediate metabolizers (IM). The final model included central and peripheral compartment for both parent (RIP) and metabolite (9-hydroxyrisperidone) respectively. Model structure identifiability analysis indicated that the proposed model was local identifiable. However, if the ratio of RIP converted to 9-hydroxyrisperidone was assumed to be 32% in EM, and 22% in IM, the model could be globally identifiable. The predicted time-concentration curve and AUC(0-t), C(max), T(max) of RIP and 9-hydroxyrisperidone estimated by the established model were in agreement with the observations and noncompartment analysis. Rate constant of RIP conversion to 9-hydroxyrisperidone was (0.12 +/- 0.08) h(-1) and (0.014 +/- 0.007) h(-1) for EM and IM, respectively. Elimination rate constants of RIP were (0.25 +/- 0.18) and (0.05 +/- 0.23) h(-1) for EM and IM, respectively. Model validation result showed that all parameters derived from the concentration data fitted well with the theoretical value, with mean prediction error of most PK parameter within +/- 15%. The established model well defined the disposition of RIP and 9-hydroxyrisperidone simultaneously and showed large inter-individual pharmacokinetics variation in different CYP2D6 phenotype. The model also provide a useful approach to characterize pharmacokinetics of other parent-metabolite drugs.

P-glycoprotein and cytochrome P450 3A4 involvement in risperidone transport using an in vitro Caco-2/TC7 model and an in vivo model

The possible involvement of P-glycoprotein (P-gp) and cytochrome P450 (CYP) 3A4 in risperidone transport was investigated using in vitro and in vivo models. Firstly, uptake studies were performed on a Caco-2/TC7 cell monolayer; the effects of 1 microg ml(-1) risperidone on apparent permeability were determined for secretory and absorptive directions, in the presence or absence of various P-gp and CYP3A4 inhibitors (verapamil, ketoconazole, erythromycin), and of an associated multidrug-resistant protein inhibitor (indomethacin). Secondly, on a conscious rat model, risperidone pharmacokinetic parameters, notably absorption parameters, were determined using compartmental and deconvolution methods. Three groups of seven rats received respectively an IV risperidone dose, an oral risperidone dose (PO group) and the same oral risperidone dose after verapamil administration (POV group). No formation of 9-hydroxyrisperidone was observed on Caco-2 cells after risperidone administration; there was no evidence that intestinal CYP3A4 is involved in risperidone metabolising. Risperidone secretory permeation was higher than absorptive permeation. Verapamil increased risperidone absorption permeation and decreased its secretory permeation. Indomethacin did not modify these permeation values. In rats, verapamil led to an increase in both risperidone and 9-hydroxyrisperidone plasmatic concentrations. The fraction absorbed in the verapamil group was 3.18 times higher than in the oral group (65.9% and 20.7% for POV group and PO group). The absorption rate constant was lower in the verapamil group. Our results indicate that P-gp decreases the intestinal absorption of risperidone and that intestinal CYP3A4 is not involved in risperidone metabolism.

Lack of bioequivalence between generic risperidone oral solution and originator risperidone tablets

Risperidone is an atypical anti-psychotic, available in various formulations.

OBJECTIVE

The objective of the study was to compare the bioavailability of a generic oral solution of risperidone (Test formulation) and Risperdal tablets (Reference formulation). Both formulations contained 1 mg risperidone per dosing unit.

METHODS

The study was carried out in 32 healthy volunteers under fasting conditions. Risperidone and 9-hydroxyrisperidone concentrations in plasma were determined using HPLC/MS/MS.

RESULTS

The results show that the 90% confidence intervals for the geometric mean ratios of the solution and the tablet formulations were not within the acceptance range of 80 125% for risperidone, whereas the confidence intervals for 9-hydroxyrisperidone were within the acceptance range of 80 - 125%.

CONCLUSION

Bioequivalence between the generic 1 mg/ml risperidone solution and the originator tablet formulation was not proven in this study.

Prolactin level during 5 years of risperidone treatment in patients with psychotic disorders

OBJECTIVE

To investigate prolactin levels and related side effects in 128 men and 90 women initially treated with risperidone.

METHOD

Patients initially treated with risperidone were followed over 5 years, during which 45% were switched to other antipsychotic drugs.

RESULTS

Initially, prolactin levels were fivefold the norm in women, and threefold in men. Diagnosis did not affect the prolactin level if adjustment for sex, current age, and age at onset of psychosis was applied. Prolactin levels did not correlate significantly neither with any Positive and Negative Symptom Scale item or subscale, nor with side effects. Drugs other than risperidone were not associated with high prolactin levels. For patients on continuous monotherapy risperidone treatment, there was a marked linear reduction of prolactin level over all 5 years.

CONCLUSION

Risperidone induces a higher prolactin elevation than other atypical antipsychotics, but the effect adapts over time. Prolactin was not associated with expected side effects (e.g. sexual, mental, or weight gain).

Prolactin elevation of the antipsychotic risperidone is predominantly related to its 9-hydroxy metabolite

OBJECTIVE

Treatment with the antipsychotic risperidone is frequently associated with hyperprolactinemia. The aim of this study was to evaluate the role of the main compound risperidone and its active 9-hydroxy metabolite on elevating prolactin levels.

METHODS

Twenty patients with psychotic disorders, on therapy with risperidone, were studied. All patients had been receiving risperidone for at least 2.5 months, and the median daily dose of risperidone was 3 mg (range 1-10). Morning serum samples for prolactin were analyzed and investigated in relation to the serum concentrations of risperidone and 9-hydroxyrisperidone.

RESULTS

Elevated prolactin levels were found in 17 (85%) of the patients. Levels of prolactin were positively correlated to the 9-hydroxyrisperidone serum concentration (r(s) = 0.48, p = 0.03) and to the daily dose of risperidone (r(s) = 0.51, p = 0.03), but did not correlate to the risperidone serum concentration.

CONCLUSION

The present results suggest that 9-hydroxyrisperidone and not risperidone is the main contributor to the increased serum levels of prolactin observed in many risperidone-treated patients.

Dopamine D2 receptor occupancy by risperidone: implications for the timing and magnitude of clinical response

The objective of the study is to investigate whether dopamine D2 receptor occupancy by risperidone and plasma levels over time can account for therapeutic efficacy and the latency period to response. Thirty-eight examinations with (123)I-IBZM single photon emission computed tomography were performed on 22 patients with schizophrenia, at diagnosis, 48 h after starting risperidone treatment and at a stable dose. Risperidone plasma levels were determined and psychopathologic evaluations (Brief Psychiatric Rating Scale, Positive and Negative Syndrome Scale) were carried out. No differences in the striatal/occipital (S/O) ratio or plasma levels were found between examinations at the 48-h time point and when a stable dose level had been established, so these parameters could not account for the latency period required for clinical response. D2 receptor occupancy at 48 h correlated positively with clinical improvement after 2 weeks of treatment. Therefore, if these results are confirmed, D2 receptor occupancy at the beginning of treatment with risperidone may be a predictor of subsequent clinical response.

The redistribution of selected psychiatric drugs in post-mortem cases

The post-mortem redistribution of a number of psychiatric drugs was investigated. A portion of liver, the gastric contents and blood collected from heart and femoral sites was obtained from 13 cases and analyzed by liquid chromatography-mass spectrometry. Drugs detected included five selective serotonin reuptake inhibitors; venlafaxine, a serotonin/noradrenaline reuptake inhibitor; and risperidone, an atypical antipsychotic. Heart blood concentrations were significantly higher (3.4-fold on average) than those measured in femoral blood when results from all drugs were included together. The range for parent drug concentrations in these two blood specimens was 0.5-6.2. There was no significant correlation of the post-mortem interval, the liver concentration and content of drugs in the gastric contents to the heart:femoral blood concentration ratio. These data serve to demonstrate that variable increases in blood concentration occur post-mortem and limit the interpretative value of such toxicological data.

Population pharmacokinetics of risperidone and 9-hydroxyrisperidone in patients with acute episodes associated with bipolar I disorder

A population model was developed with the aim to simultaneously describe risperidone and 9-hydroxyrisperidone pharmacokinetics; to obtain estimates for pharmacokinetic parameters and associated inter- and intra-individual variability of risperidone and 9-hydroxyrisperidone; and to evaluate the influence of patient demographic characteristics and other factors on risperidone, 9-hydroxyrisperidone, and active moiety pharmacokinetics. Data were obtained from 407 patients enrolled in four Phase 1 (serial blood sampling) and three Phase 3 trials (sparse sampling), representing dosage regimens ranging from 4 mg single dose to flexible 1-6 mg once daily. A pharmacokinetic model with two-compartment submodels for risperidone and 9-hydroxyrisperidone disposition and a sequential zero- and first-order absorption pathway was selected based on prior knowledge. A mixture model was incorporated due to CYP2D6 polymorphism of risperidone conversion to 9-hydroxyrisperidone. Patient characteristics tested as potential covariates were: age, sex, race, body weight, lean body mass, body mass index, creatinine clearance, liver function laboratory parameters, study, and carbamazepine comedication. The quasi-clearance of active moiety (the sum of risperidone and 9-hydroxyrisperidone) was simulated and linear regression performed to identify significant covariates. The selected pharmacokinetic model described the plasma concentration-time profiles for risperidone and 9-hydroxyrisperidone quite well and was able to determine each patient's phenotype. Covariates significantly affecting the pharmacokinetics were carbamazepine comedication, and study because the proportion of patients assigned to the intermediate metabolizer status decreased from single to multiple dosing while the proportion assigned to extensive metabolizer status increased. Covariates with limited and clinically irrelevant effects on active moiety concentrations were patient phenotype, race, and total protein. Carbamazepine also decreased active moiety concentrations.