Aripiprazole and dehydroaripiprazole plasma concentrations and clinical responses in patients with schizophrenia

Therapeutic drug monitoring in children and adolescents with schizophrenia-spectrum, affective, behavioural, tic and other psychiatric disorders treated with aripiprazole: results of the TDM-VIGIL pharmacovigilance study

Aripiprazole is approved for various severe mental disorders in adults and adolescents. However, off-label prescribing is common, especially in children and adolescents (youth) in whom aripiprazole therapeutic serum level reference ranges are lacking for any disorders. The aim of the study was to evaluate the relationship between aripiprazole dose and serum concentrations and provide further knowledge on the use of aripiprazole in order to improve drug safety and effectiveness in the treatment of minors. The clinical course of youth treated with aripiprazole in the multicentre pharmacovigilance study TDM-VIGIL was systematically followed and serum concentrations measured. Sex, age, weight and comedications were analysed to identify possible effect modifiers. A preliminary therapeutic reference range was estimated for youth with schizophrenia-spectrum disorders, affective disorders and behavioural/emotional/tic disorders coded as treatment responders based on a Clinical-Global Impressions-Improvement (CGI-I) score of much or very much improved. In 93 youth (mean age = 15.2 ± 2.6, range = 7.4-18.2 years, females = 53%, CGI-Severity = 4.4 ± 1.1, responders = 64%), a positive, moderate correlation between the weight-normalized daily dose (WNDD) and aripiprazole serum concentration (=0.791, p < 0.0001) was found. The WNDD and co-medications that interact with CYP2D6 and CYP3A4 affected aripiprazole serum levels, explaining 64% of the variance. In patients within the preliminary therapeutic ranges determined by interquartile ranges (IQRs), slightly better outcomes and fewer adverse drug reactions were found versus patients within preliminary therapeutic ranges determined by the mean ± SD. The preliminary reference range for paediatric patients with schizophrenia-spectrum disorders calculated by the IQR showed an identical lower threshold (100-230 ng/ml) compared to adult schizophrenia-spectrum disorders patients (100-350 ng/ml). The preliminary therapeutic ranges for patients with affective disorders was: 60-160 ng/ml and for patients with behavioural/tic disorders 60-140 ng/ml. The therapeutic reference ranges for aripiprazole in youth estimated via the 25th and 75th IQRs may result in more clinically relevant therapeutic windows. Further studies need to confirm these results, especially in patients with affective and behavioural/tic disorder diagnoses.

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

BACKGROUND

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

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

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

CONCLUSION

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

Verification of successful maintenance by serum drug level during a guided antipsychotic reduction to reach minimum effective dose (GARMED) trial

BACKGROUND

Inconsistent results regarding the risk of relapse and better subjective outcomes of previous antipsychotic dose reduction trials in patients with remitted psychosis have not been verified using therapeutic drug monitoring (TDM). This study examined plasma drug concentrations of a dose-tapering trial which exhibited the potential of successful maintenance under lower antipsychotic dosages.

METHODS

A 2-year open-label randomized prospective trial recruited remitted patients to undergo guided antipsychotic tapering. Blood samples were collected at baseline, annually, and after each dose reduction. Plasma aripiprazole/dehydroaripiprazole concentrations were determined using LC-MS/MS. The relationship between the dose and serum drug levels was examined using Spearman's correlation. Divided at 120 ng/mL, relapse rate, global function, quality of life, and psychopathology were compared between high- and low- drug level groups.

RESULTS

A total of 126 blood samples were collected, after excluding13 samples due of non-adherence. The correlation coefficients between dosage and drug level were 0.853 (aripiprazole) and 0.864 (dehydroaripiprazole), and the dose and concentration plots were parallel along the tapering trajectories, except patients with non-adherence. The concentration-to-dose ratio of aripiprazole in this cohort, 17.79 ± 7.23 ng/mL/mg, was higher than that in Caucasian populations. No significant differences were observed in the clinical outcomes between the high- and low-level groups. Remarkably, 12 of 15 patients maintained remission at plasma aripiprazole concentrations of <120 ng/mL.

CONCLUSIONS

The lower-than-expected doses reached in our antipsychotic tapering trial were substantiated to provide adequate prophylactic effects by TDM results in a subset of patients treated with aripiprazole, even considering the differences in pharmacogenomics between ethnicities.

Towards precision medicine of long-acting aripiprazole through population pharmacokinetic modelling

Population pharmacokinetic (popPK) models constitute a valuable tool for characterizing the pharmacokinetic properties of once-monthly long-acting injectable aripiprazole (LAI aripiprazole) and quantifying the sources of variability in drug exposure. Our aim is to develop a popPK model of both aripiprazole and its metabolite dehydro-aripiprazole in patients treated with LAI aripiprazole, and to personalize the dosing regimen of aripiprazole across different sub-groups of patients. This is a prospective study investigating the pharmacokinetics of LAI aripiprazole. A total of 93 patients were included, 21 for model development and 71 for external model evaluation. A one-compartment model with linear absorption and elimination adequately described both aripiprazole and dehydro-aripiprazole concentrations. The weight of the patients has been shown to be the factor that most influences the absorption. However, the metabolizing phenotype for CYP2D6 and the concomitant treatment with strong inhibitors of this cytochrome have been shown to be the covariates that most influence total drug exposure. This is the first popPK model developed for LAI aripiprazole that includes aripiprazole and its main active metabolite, dehydroaripiprazole. It provides a personalized dosage recommendation that maximizes the probability of achieving optimal therapeutic concentrations and minimizes the difficulties associated with trial-and-error therapeutic strategies carried out in clinical practice.

Long-Acting Injectable Second-Generation Antipsychotics in Seriously Ill Patients with Schizophrenia: Doses, Plasma Levels, and Treatment Outcomes

This research studies the dose-plasma level (PL) relationship of second-generation antipsychotics, together with the treatment outcomes achieved, in seriously ill people with schizophrenia. An observational, prospective, one-year follow-up study was carried out with patients (N = 68) with severe schizophrenia treated with paliperidone three-month (PP3M) or aripiprazole one-month (ARIM). Participants were divided into standard-dose or high-dose groups. PLs were divided into "standard PL" and "high PL" (above the therapeutic reference range, TRR) groups. The dose/PL relationship, and severity, hospitalizations, tolerability, compliance, and their relationship with doses and PLs were evaluated. There was no clear linear relationship between ARIM or PP3M doses and the PLs achieved. In half of the subjects, standard doses reached PLs above the TRR. The improvements in clinical outcomes (decrease in clinical severity and relapses) were related to high PLs, without worse treatment tolerability or adherence. All participants remained in the study, regardless of dose or PL. Clinical severity and hospitalizations decreased significantly more in those patients with high PLs. Considering the non-linear dose-PL relationship of ARIM and PP3M in people with severe schizophrenia, PLs above the TRR are linked to better treatment outcomes, without worse tolerability. The need in a notable number of cases for high doses to reach those effective PLs is highlighted.

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

AIM

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Plasmatic Levels and Response to Variable Doses of Monthly Aripiprazole and Three-Month Paliperidone in Patients with Severe Schizophrenia. Treatment Adherence, Effectiveness, Tolerability, and Safety

Introduction

There is a need when optimizing antipsychotic treatment to know the plasmatic levels (PLs) achieved with the different doses and their relationship with effectiveness and toxicity, especially in patients with poor clinical progress. This study investigates the dose-PL-response relationship of monthly aripiprazole (AOM) and three-month paliperidone (PP3M).

Methods

Observational, 52-week prospective study of patients with severe schizophrenia (CGI-S ≥ 5) treated with PP3M or AOM for at least one year before their inclusion in the study (N=68). Dose-PL relationship was determined. Subjects were included in standard-dose and high-dose (above labeled) and standard/therapeutic range-PLs and high-PLs (above range) groups. Treatment adherence, effectiveness (hospitalizations, severity), tolerability and safety were assessed. PLs and clinical response were evaluated.

Results

No clear linear relationship was found between doses and PLs. In a considerable number of cases, standard doses achieved PLs above the therapeutic range. A significant clinical improvement was related to high PLs, without less safety, tolerability, or treatment compliance being involved. Clinical severity decreased more frequently in patients who received high doses and reached high PLs. Hospital admissions decreased significantly in those patients with high PLs.

Conclusion

Taking into account the absence of a linear relationship between doses and PLs, the effectiveness in people with severe schizophrenia of AOM and PP3M depends on reaching high PLs, achieved with high doses, but also with standard doses in some cases, without leading to worse treatment tolerability, safety, or adherence.

Post-therapy plasma concentrations of quetiapine in Taiwanese patients

AIMS

Quetiapine is widely used to treat psychiatric disorders such as major depression, generalized anxiety disorder, dysthymic disorder, and insomnia other than schizophrenia and bipolar disorder. This study investigated the diagnostic distribution of quetiapine use in patients in a psychiatric hospital, the doses of quetiapine prescribed, and the plasma concentrations (Cps) of quetiapine and active metabolites.

METHODS

We enrolled 107 patients who had been prescribed quetiapine for at least 4 weeks. Diagnoses, demographics, and concomitant medications were recorded. Blood sampling was performed in the morning, approximately 12 h after the before-bed dose of quetiapine.

RESULTS

Diagnoses comprised schizophrenia (n = 25), bipolar disorder (n = 51), major depression (n = 15), dysthymic disorder (n = 9), and others (n = 7). The daily dose (DD) of quetiapine ranged from 25 to 800 (175.9 ± 184.4) mg, with the mean Cp being 105.6 ± 215.3 ng/ml, with a mean Cps/DD ratio of 0.58 ± 0.55 ng/ml/mg. There was a moderate positive linear correlation between the dose and Cps of quetiapine (r = 0.60), and the interpatient variation in Cps/DD ratio was up to 26-fold.

CONCLUSION

Quetiapine is used in various doses to treat many psychiatric disorders other than psychosis, and it is usually prescribed as a secondary antipsychotic for symptoms such as insomnia or agitation. A wide interpatient variation of the Cps/DD ratio was noticed. Patients of East Asian descent may exhibit a 50% to 100% increase in the Cps/DD ratio for quetiapine compared with patients of Western descent.

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

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

Therapeutic Reference Range for Aripiprazole in Schizophrenia Revised: a Systematic Review and Metaanalysis

RATIONALE

While one of the basic axioms of pharmacology postulates that there is a relationship between the concentration and effects of a drug, the value of measuring blood levels is questioned by many clinicians. This is due to the often-missing validation of therapeutic reference ranges.

OBJECTIVES

Here, we present a prototypical meta-analysis of the relationships between blood levels of aripiprazole, its target engagement in the human brain, and clinical effects and side effects in patients with schizophrenia and related disorders.

METHODS

The relevant literature was systematically searched and reviewed for aripiprazole oral and injectable formulations. Population-based concentration ranges were computed (N = 3,373) and pharmacokinetic influences investigated.

RESULTS

Fifty-three study cohorts met the eligibility criteria. Twenty-nine studies report blood level after oral, 15 after injectable formulations, and nine were positron emission tomography studies. Conflicting evidence for a relationship between concentration, efficacy, and side effects exists (assigned level of evidence low, C; and absent, D). Population-based reference ranges are well in-line with findings from neuroimaging data and individual efficacy studies. We suggest a therapeutic reference range of 120-270 ng/ml and 180-380 ng/ml, respectively, for aripiprazole and its active moiety for the treatment of schizophrenia and related disorders.

CONCLUSIONS

High interindividual variability and the influence of CYP2D6 genotypes gives a special indication for Therapeutic Drug Monitoring of oral and long-acting aripiprazole. A starting dose of 10 mg will in most patients result in effective concentrations in blood and brain. 5 mg will be sufficient for known poor metabolizers.

Racial/Ethnic Differences in the Pharmacokinetics of Antipsychotics: Focusing on East Asians

Empirical clinical studies have suggested that East Asian patients may require lower dosages of psychotropic drugs, such as antipsychotics, lithium, and antidepressants, than non-Asians. Both the pharmacokinetic and pharmacodynamic properties of a drug can affect the clinical response of an illness. The levels of antipsychotics used for the treatment of schizophrenia may affect patient clinical responses; several factors can affect these levels, including patient medication adherence, body weight (BW) or body mass index, smoking habits, and sex. The cytochrome P450 (CYP) system is a major factor affecting the blood levels of antipsychotics because many antipsychotics are metabolized by this system. There were notable genetic differences between people of different races. In this study, we determined the racial or ethnic differences in the metabolic patterns of some selected antipsychotics by reviewing therapeutic drug monitoring studies in East Asian populations. The plasma concentrations of haloperidol, clozapine, quetiapine, aripiprazole, and lurasidone, which are metabolized by specific CYP enzymes, were determined to be higher, under the same daily dose, in East Asian populations than in Western populations.

Concentrations of aripiprazole and dehydroaripiprazole in hair segments from deceased individuals with mental disorders

Segmental hair analysis provides information regarding previous long-term drug exposure, which is useful in the evaluation of cause of death for individuals with mental disorders. The aim was to analyze postmortem concentrations of the antipsychotic drug aripiprazole and its active metabolite dehydroaripiprazole in hair segments from individuals with known aripiprazole intake. Hair samples were collected during autopsy. Each sample was segmented into one to six 1cm segments, depending on the length of the hair shaft. Pulverized hair was extracted and analyzed using a previously published ultra-high-performance liquid chromatography-tandem mass spectrometric method. The 10th-90th percentile of aripiprazole concentrations in all hair segments (n=78) from 17 individuals were 0.024ng/mg-11ng/mg with a median of 2.3ng/mg, and the 10th-90th percentile concentrations of dehydroaripiprazole were 0.020ng/mg-11ng/mg, with a median of 2.6ng/mg, in all hair segments (n=71). The metabolite-to-parent drug ratios ranged from 0.21 to 1.5, with a median of 0.72. The administered doses were calculated for each individual based on aripiprazole prescription data and pharmacy pickups, giving dose estimates of 1mg-32mg daily. A positive significant correlation was observed between concentrations in hair and blood, whereas no trends were observed between the concentrations in hair and the estimated doses. Besides aripiprazole, other antipsychotic drugs were found in several hair segments, indicating a high degree of polypharmacy among all subjects. The present study establishes concentrations of aripiprazole and dehydroaripiprazole in hair segments from 17 deceased individuals with long-term aripiprazole use. In addition, hair analysis demonstrates the possibility of evaluating polypharmacy.

Phenoconversion of CYP2D6 by inhibitors modifies aripiprazole exposure

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

Aripiprazole Long-Acting Injection During First Episode Schizophrenia-An Exploratory Analysis

Background: Long-acting injectable (LAI) aripiprazole was found to be efficacious in schizophrenia. In common clinical practice, the use of LAIs is often restricted to chronic patients with frequent relapses and poor adherence. Recently, some investigators advanced the idea of early LAI use also in young people with schizophrenia at their first psychotic episode (FEP). Objective: Our study aimed to assess the effect of LAI aripiprazole once monthly (AOM) in the treatment of FEP in patients aged 18-26 years. Methods: We included 50 patients with DSM-5 schizophrenia as assessed with SCID, and used the Clinical Global Impressions Scale-Severity of Illness (CGI-S) and the Positive and Negative Syndrome Scale (PANSS) to assess symptom severity and the World Health Organization Quality of Life (WHOQOL), the Short Form Health Survey (SF-36) and the Personal and Social Performance Scale (PSP) to assess quality of life (QoL) and global health perception at baseline and 3, 6, 9, and 12 months after the first AOM injection. Results: AOM was associated with a progressive improvement, compared to baseline, of both positive (p < 0.001) and negative (p < 0.001) symptoms and in general psychopathology (p < 0.001) and decrease in global severity (p < 0.001). We also observed progressive improvement in QoL and social and personal functioning. Treatment adherence was 78% at study endpoint. Our results support that AOM may improve psychotic symptoms, QoL and social functioning in young FEP patients. Further studies should compare AOM to its oral formulation in the treatment of young patients with schizophrenia at the outset of their illness.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Paliperidone and aripiprazole differentially affect the strength of calcium-secretion coupling in female pituitary lactotrophs

Hyperprolactinemia is a common adverse in vivo effect of antipsychotic medications that are used in the treatment of patients with schizophrenia. Here, we compared the effects of two atypical antipsychotics, paliperidone and aripiprazole, on cAMP/calcium signaling and prolactin release in female rat pituitary lactotrophs in vitro. Dopamine inhibited spontaneous cAMP/calcium signaling and prolactin release. In the presence of dopamine, paliperidone rescued cAMP/calcium signaling and prolactin release in a concentration-dependent manner, whereas aripiprazole was only partially effective. In the absence of dopamine, paliperidone stimulated cAMP/calcium signaling and prolactin release, whereas aripiprazole inhibited signaling and secretion more potently but less effectively than dopamine. Forskolin-stimulated cAMP production was facilitated by paliperidone and inhibited by aripiprazole, although the latter was not as effective as dopamine. None of the compounds affected prolactin transcript activity, intracellular prolactin accumulation, or growth hormone secretion. These data indicate that paliperidone has dual hyperprolactinemic actions in lactotrophs i) by preserving the coupling of spontaneous electrical activity and prolactin secretion in the presence of dopamine and ii) by inhibiting intrinsic dopamine receptor activity in the absence of dopamine, leading to enhanced calcium signaling and secretion. In contrast, aripiprazole acts on prolactin secretion by attenuating, but not abolishing, calcium-secretion coupling.

[Efficacy of aripiprazole for the treatment of schizophrenia: what dose is required?]

OBJECTIVE

Problem of the choice of antipsychotic dose is a key issue in clinical practice. It determines the efficacy and safety of treatment. Aripiprazole is recommended at a dose of between 10 and 15 mg/day in the treatment of schizophrenia, with a dose range considered to be effective, between 10 and 30 mg/day. This wide therapeutic range prompted us to investigate the existence of a possible dose-effect relationship for aripiprazole in the treatment of schizophrenia.

METHOD

We conducted a literature review from PubMed and EMBASE database, with the keywords: aripiprazole, schizophrenia. We limited it to studies published in English and French, with the main objective to assess the efficacy of aripiprazole in patients with schizophrenia. We selected only randomized clinical trials, double-blind, controlled against placebo or against an active comparator. Studies in which aripiprazole was studied added to another antipsychotic were not retained.

RESULTS

Twenty-two randomized, double-blind, controlled studies were selected. Three studies assessed the efficacy of aripiprazole on agitation symptoms in patients with schizophrenia and for which a dose of aripiprazole between 1 and 15mg showed significant efficacy compared to placebo. Seven clinical trials focused on the effect of aripiprazole short term (less than 12weeks). For the primary endpoint (PANSS scores), aripiprazole was superior to placebo or equivalent to active comparators (risperidone, olanzapine or haloperidol). These short-term studies revealed a range of effective doses from 10 mg/day to 20 mg/day. Five studies, lasting between 16 and 52 weeks, with a primary endpoint being the time to discontinuation for any cause for two studies, the time before relapse in one study, and the improvement in PANSS scores for the two other studies. On these different endpoints, aripiprazole was effective at average doses between 15 and 28.1 mg/day. The safety of aripiprazole was particularly favourable in these trials. Finally, we listed seven post-hoc analyses. In support of these long-term analyses on different endpoints, aripiprazole showed significant efficacy at higher doses (20 and 30 mg/day) than those used in the agitation treatment.

CONCLUSIONS

No study was designed to compare aripiprazole doses in schizophrenia. Nevertheless, efficacy on agitation and hostility components had been observed for doses of 10mg/day, or lower; whereas the antipsychotic effect in acute or maintenance phase appeared optimal for doses ranging from 10 to 25 mg/day. Only one study retained a minimum effective dose of 10mg/day on the PANSS scores. This literature review reveals an effective dose range between 10 and 25 mg/day for aripiprazole in schizophrenia. Less than 10 mg/day did not show significant efficacy on symptoms of schizophrenia, apart from a specific short-term effect on agitation, at very low doses (starting at 1mg). Optimization of treatment, at doses above 25 mg/day, cannot be the subject of evidence-based recommendations.

Plasma levels of second-generation antipsychotics and clinical response in acute psychosis: a review of the literature

OBJECTIVE

The objective of the study is to assess the relationships between plasma concentrations (Cps) of second-generation antipsychotics (SGAs) and clinical outcome in order to establish the clinical value of therapeutic drug monitoring.

METHOD

In April 2012, we searched PubMed and MEDLINE databases for English-language articles using the keywords risperidone, olanzapine, quetiapine, aripiprazole, ziprasidone, paliperidone, iloperidone, asenapine, lurasidone, therapeutic drug monitoring, serum level, and plasma level. One hundred and ninety-one articles were retrieved from the initial search. Articles were selected for inclusion if they involved an attempt to correlate Cps with efficacy measures, if they were prospective in nature, and if they examined patients experiencing an acute exacerbation of a psychotic illness. Ultimately 11 articles were selected.

RESULTS

Of the nine compounds involved in the search, only four were included in relevant articles, and only two of these were involved in multiple trials. No studies involving the most recently developed compounds (paliperidone, iloperidone, asenapine, and lurasidone) were identified. Studies varied widely in methodology, with only four studies adopting a fixed-dose model. Results differed considerably between studies regarding both clinical and adverse effects, with 6 of the 11 studies revealing a positive correlation between Cps and response.

CONCLUSIONS

The utility of therapeutic drug monitoring of SGAs (other than clozapine) remains an open question, although limited evidence from fixed-dose studies is encouraging. We discuss the potentially significant clinical value of antipsychotic Cps and the consequent need for further research in this area.