Plasma Concentrations Of Aripiprazole Research Articles

Role of CYP2D6 and CYP3A4 polymorphisms on aripiprazole and dehydroaripiprazole concentrations in patients undergoing long-acting treatment

Aripiprazole once-monthly (AOM) exhibits an important interindividual pharmacokinetic variability with significant implications for its clinical use. CYP2D6 and CYP3A4 highly contributes to this variability, as they metabolize aripiprazole (ARI) into its active metabolite, dehydroaripiprazole (DHA) and the latter into inactive metabolites.This study aims to evaluate the effect of CYP2D6 and CYP3A4 polymorphisms in combination and the presence of concomitant inducers and inhibitors of this cytochromes on ARI and DHA plasma concentrations in a real clinical setting.An observational study of a cohort of 74 Caucasian patients under AOM treatment was conducted. Regarding CYP2D6, higher concentrations were found for active moiety (ARI plus DHA) (AM) (67 %), ARI (67 %) and ARI/DHA ratio (77 %) for poor metabolizers (PMs) compared to normal metabolizers (NMs). No differences were found for DHA.PMs for both CYP2D6 and CYP3A4 showed a 58 % higher AM and 66 % higher plasma concentration for ARI compared with PMs for CYP2D6 and NMs for CYP3A4. In addition, PMs for both CYP2D6 and CYP3A4 have 45 % higher DHA concentrations than NMs for both cytochromes and 41 % more DHA than PMs for CYP2D6 and NMs for CYP3A4, suggesting a significant role of CYP3A4 in the elimination of DHA.Evaluating the effect of CYPD26 and CYP3A4 metabolizing state in combination on plasma concentrations of ARI, DHA and parent-to-metabolite ratio, considering concomitant treatments with inducers and inhibitor, could optimize therapy for patients under AOM treatment.

Population Pharmacokinetics and Dosing Simulations for Aripiprazole 2-Month Ready-to-Use Long-Acting Injectable in Adult Patients With Schizophrenia or Bipolar I Disorder.

A ready-to-use (RTU) long-acting injectable (LAI) formulation of aripiprazole monohydrate for administration once every 2 months, available in 960 mg (Ari 2MRTU 960) or 720 mg doses, has been developed for the treatment of schizophrenia or bipolar I disorder. A previously developed and validated population pharmacokinetic model for characterizing aripiprazole plasma concentrations following administration of oral aripiprazole or aripiprazole once-monthly (AOM) intramuscular injection was expanded to include the RTU LAI formulation of aripiprazole (Ari RTU LAI). Overall, 8899aripiprazole pharmacokinetic samples from 1191 adults from 10 clinical trials were included in the final combined analysis data set. Aripiprazole plasma concentration-time profiles were simulated for various Ari RTU LAI initiation and maintenance scenarios in 1000 virtual patients. Diagnostic plots demonstrated that the final population pharmacokinetic model, which incorporated data for oral aripiprazole, AOM, and Ari RTU LAI, adequately described aripiprazole concentrations following Ari RTU LAI administration. Absorption of Ari RTU LAI was modeled by a parallel zero-order and lagged first-order process. Simulations across multiple scenarios were performed to inform dosing recommendations, including various treatment initiation regimens for a 2-monthly formulation of Ari RTU LAI in patients with or without prior stabilization on oral aripiprazole, and for patients switching from AOM. Additional simulations accounted for missed/delayed doses, cytochrome (CYP) 2D6 metabolizer status, and concomitant use of CYP2D6 or CYP3A4 inhibitors. Overall, simulations across a variety of scenarios demonstrated an Ari RTU LAI pharmacokinetic exposure profile that was comparable to AOM, with a longer dosing interval.

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

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

Comment on "Aripiprazole Plasma Concentrations Delivered from Two 2-Month Long-Acting Injectable Formulations: An Indirect Comparison" [Letter

Comment on "Aripiprazole Plasma Concentrations Delivered from Two 2-Month Long-Acting Injectable Formulations: An Indirect Comparison" [Letter

Aripiprazole Plasma Concentrations Delivered from Two 2-Month Long-Acting Injectable Formulations: An Indirect Comparison.

Aripiprazole 2-month ready-to-use 960 mg (Ari 2MRTU 960) is a novel long-acting injectable (LAI) formulation of aripiprazole monohydrate for administration once every 2 months, developed for the treatment of schizophrenia or maintenance monotherapy treatment of bipolar I disorder in adults (indication will vary by country). Aripiprazole lauroxil 1064 mg (AL 1064) is an LAI formulation of aripiprazole lauroxil, an aripiprazole prodrug, for administration once every 2 months, indicated for the treatment of schizophrenia in adults. This analysis provides an indirect comparison of aripiprazole plasma concentrations following multiple doses of either formulation. Clinical trial data were used to determine average steady-state aripiprazole plasma concentration (Cavg,ss), maximum aripiprazole plasma concentration (Cmax), and other pharmacokinetic parameters of either formulation following four administrations (96 patients received Ari 2MRTU 960; 28 patients received AL 1064). All pharmacokinetic parameters were considered in the context of a minimum aripiprazole therapeutic concentration (Cmin) of ≥95 ng/mL. An exposure-response analysis using data from two Phase III trials of aripiprazole once-monthly (an aripiprazole monohydrate LAI, administered monthly), showed that patients with a Cmin ≥95 ng/mL are 4.41 times less likely to relapse than patients with a Cmin <95 ng/mL. A similar analysis has not been performed for AL 1064. However, consensus guidelines for therapeutic drug monitoring recommend a range of 100-350 ng/mL for aripiprazole. Following four administrations, mean (standard deviation [SD]) Cavg,ss over the 2-month dosing interval was 263 (133) ng/mL for Ari 2MRTU 960 and 140.7 (57.3) ng/mL for AL 1064. Mean (SD) Cmax during the fourth dosing interval was 342 (157) ng/mL for Ari 2MRTU 960 and 188.8 (79.8) ng/mL for AL 1064. This indirect comparison showed that, following four administrations, Ari 2MRTU 960 and AL 1064 delivered mean aripiprazole plasma concentrations that remained above the minimum therapeutic concentration of aripiprazole over the 2-month dosing interval.

Med Check: Zuranolone for Depression, Uzedy for Schizophrenia, and More

Back to table of contents Previous article Next article Med CheckFull AccessMed Check: Zuranolone for Depression, Uzedy for Schizophrenia, and MoreTerri D’ArrigoTerri D’ArrigoSearch for more papers by this authorPublished Online:25 May 2023https://doi.org/10.1176/appi.pn.2023.06.6.1Zuranolone Found to Quickly Reduce Major Depression SymptomsAdults with major depressive disorder may experience mood improvements within days of taking zuranolone (50 mg/day), a study published in May in The American Journal of Psychiatry (AJP) suggests. Zuranolone is an oral, once-daily neuroactive steroid that acts on GABA-A receptors.The phase 3 trial included patients who were between the ages of 18 and 64 years, had received a diagnosis of major depressive disorder, had been experiencing symptoms of depression for a least four weeks, and had a Hamilton Depression Rating Scale (HAM-D) score of at least 24 at screening and before they started taking the assigned study medication.The researchers randomized 534 participants to take either 14 days of treatment with zuranolone 50 mg/day or placebo in the evening. The researchers evaluated the participants 10 times over the course of the 42-day trial using such assessments as the HAM-D, the Columbia–Suicide Severity Rating Scale, the Clinical Global Impressions severity score, and more.Compared with patients who took placebo, those who took zuranolone demonstrated a statistically significant improvement in depressive symptoms at day 15. “Numerically greater improvements in depressive symptoms for zuranolone versus placebo were observed by day 3 (least squares mean change from baseline HAM-D score, −9.8 vs. −6.8), which were sustained at all visits throughout the treatment and follow-up periods of the study,” the researchers wrote.FDA Approves Uzedy for Treating SchizophreniaIn April the U.S. Food and Drug Administration (FDA) approved Uzedy (risperidone extended-release injectable suspension) for the treatment of schizophrenia in adults, Teva and MedinCell announced. Uzedy is a long-acting subcutaneous antipsychotic that may be given in one- or two-month dosing intervals.In the phase 3 RISE trial, 544 patients aged 13 to 65 years with schizophrenia were randomized to receive a subcutaneous injection of Uzedy (either once per month or once every two months) or placebo. Those who received Uzedy once per month or once every two months had a reduction of 80.0% and 62.5% in the risk to relapse compared with those who received placebo, respectively. Results were similar in the phase 3 SHINE trial, which examined the long-term safety of the drug for up to 56 weeks in 336 patients aged 13 to 65 years with schizophrenia.A companion survey of participants in the SHINE trial found that 89% of patients and 92% of health professionals rated administration of Uzedy as easy when asked how easy or difficult it was to receive or administer the medication in its current form. Further, 70% of patients reported that Uzedy provided a better injection experience than their previous long-acting injectables (LAIs).Abilify Asimtufii Approved for Schizophrenia, Bipolar I TreatmentAbilify Asimtufii (aripiprazole extended release injectable suspension) has been approved by the FDA for the treatment of schizophrenia in adults and as a monotherapy treatment of bipolar I disorder in adults, Otsuka and Lundbeck announced in April. Abilify Asimtufii is a long-acting subcutaneous atypical antipsychotic that may be given every two months.The approval was based on safety and efficacy data from trials of Abilify Maintena, which is for once monthly dosing, and on the results of a phase 1-2 study. In the phase 1-2 study, 266 adults with schizophrenia or bipolar I disorder were randomly assigned to receive either Abilify Asimtufii 960 mg every 56 days, for a total of four injections or Abilify Maintena 400 mg administered every 28 days for a total of eight injections. Treatment with Abilify Asimtufii resulted in similar aripiprazole plasma concentrations and efficacy to Abilify Maintena. ■ ISSUES NewArchived

Discovering interactions in augmentation strategies: Impact of duloxetine on the metabolism of aripiprazole.

We aimed to unravel potential pharmacokinetic interactions between aripiprazole and duloxetine. Plasma concentrations of aripiprazole in two groups of 78 patients each, receiving aripiprazole as a monotherapy or combined with duloxetine, were compared. A potential impact of duloxetine on the metabolism of aripiprazole was expected in higher plasma concentrations of aripiprazole and higher dose-adjusted plasma concentrations. Patients co-medicated with duloxetine showed significantly higher plasma concentrations of aripiprazole by 54.2% (p= 0.019). Dose-adjusted plasma concentrations were 45.6% higher (p= 0.001); 12.8% of these patients exhibited aripiprazole plasma concentrations above the upper limit of the therapeutic reference range, in the control group this was only the case for 10.3% of the patients. A positive relationship was found between the daily dose of duloxetine and dose-adjusted plasma concentrations of aripiprazole (p= 0.034). As dehydroaripiprazole concentrations were not available, conclusions for the active moiety (aripiprazole plus dehydroaripiprazole) could not be drawn. Combining duloxetine and aripiprazole leads to significantly higher drug concentrations of aripiprazole, most likely via an inhibition of cytochrome P450 CYP2D6 and to a lesser extent of CYP3A4 by duloxetine. Clinicians have to consider increasing aripiprazole concentrations when adding duloxetine to a treatment regimen with aripiprazole.

Relationship Between Plasma Aripiprazole and Dehydroaripiprazole Concentrations and Prolactin Levels in Chinese Children and Adolescents.

Objective: To investigate the relationship between plasma aripiprazole (ARI) and its metabolite dehydroaripiprazole (DARI) concentrations and prolactin (PRL) levels in Chinese children and adolescents. Methods: This was a retrospective cross-sectional study and the data were collected at Beijing HuiLongGuan Hospital, a Beijing City owned psychiatric hospital, between January 1 and December 31, 2021. Fifty-two child and adolescent inpatients (17 males, 35 females) aged 13-18 years and received ARI regardless of diagnosis were included. The steady-state ARI and DARI plasma concentrations were measured using high-performance liquid chromatography-tandem mass spectrometry. The serum PRL levels were measured by chemiluminescence immunoassay. Results: The plasma concentrations of ARI, DARI, and the total of ARI and DARI were negatively correlated with serum PRL levels in female children and adolescents. Approximately 15% of child and adolescent inpatients treated with ARI exhibited subnormal PRL serum levels. Conclusions: The results suggest that in addition to regularly monitoring PRL levels, therapeutic drug monitoring for ARI and its main metabolite DARI can help to mitigate the adverse medical consequences associated with PRL reduction. Thus, clinicians should consider the ARI-induced reduction of PRL levels when prescribing ARI to child and adolescent patients, particularly among females.

Med Check: Lecanemab; ANEB-001; Azstarys; and More

Back to table of contents Previous article Next article Med CheckFull AccessMed Check: Lecanemab; ANEB-001; Azstarys; and MoreTerri D’ArrigoTerri D’ArrigoSearch for more papers by this authorPublished Online:27 Oct 2022https://doi.org/10.1176/appi.pn.2022.11.11.2Lecanemab May Slow Decline in Alzheimer’sLecanemab, an investigational anti-amyloid beta protofibril antibody, may slow cognitive decline in Alzheimer’s disease, Biogen Inc. and Esai Co. Ltd. announced in September. Lecanemab is being developed for the treatment of mild cognitive impairment from Alzheimer’s disease and mild or early Alzheimer’s disease with confirmed presence of amyloid pathology in the brain.In the phase 3 Clarity AD trial, 1,795 patients with early Alzheimer’s disease were randomized to receive either placebo or biweekly doses of 10 mg of lecanemab per kilogram of body weight. The primary endpoint was reduced clinical decline, as measured by the Clinical Dementia Rating-Sum of Boxes (CDR-SB). At the end of 18 months, CDR-SB scores had declined by 27% less in patients who received lecanemab compared with those who received placebo. The CDR-SB scores were a mean 0.45 points lower for those who received lecanemab compared with those who received placebo.Last year the Food and Drug Administration (FDA) granted Breakthrough Therapy designation to lecanemab based on the results of a phase 2b clinical trial, which examined the impact of treatment with lecanemab on reducing amyloid beta and clinical decline, as measured by changes on the Alzheimer’s Disease Composite Score (ADCOMS). Breakthrough Therapy designation expedites the development and review of drugs for serious conditions.In the trial, 856 patients who had mild cognitive impairment due to Alzheimer’s disease or mild Alzheimer’s disease dementia were randomized to receive 2.5 mg/kg, 5 mg/kg, or 10 mg/kg of lecanemab once every two weeks; 5 mg/kg or 10 mg/kg of lecanemab once every four weeks; or placebo for 18 months. Patients who took 10 mg/kg biweekly lecanemab had a 76% probability of achieving 25% less decline on ADCOMS compared with those who took placebo. ANEB-001 May Reverse Cannabinoid IntoxicationA phase 2 trial of the investigational cannabinoid receptor agonist ANEB-001 suggests that the medication may reverse cannabinoid intoxication, Anebulo Pharmaceuticals Inc. announced in September.The trial involved approximately 60 participants, who were given 21 mg of delta-9-tetrahydrocannabinol (THC). They were then given 10 mg of ANEB-001, 30 mg of ANEB-001, or placebo.Those who received placebo reported a substantial increase in feeling high and body sway, decreased alertness, and a slightly increased heart rate from baseline. Participants who received either 10 mg or 30 mg of ANEB-001 experienced significant reductions in the visual analog scale (VAS) score for feeling high, improvement in the VAS alertness scale, and a reduction in THC-induced body sway compared with those who received placebo. Azstarys May Improve Sleep for Children with ADHDAzstarys (serdexmethylphenidate and dexmethylphenidate) may help improve sleep in children with attention-deficit/hyperactivity disorder (ADHD), Corium Inc. announced in September. Azstarys is approved for the treatment of ADHD in patients aged six years and older.In a one-year open-label study, 238 children with ADHD aged six to 12 years received Aztarys for one year. After one month of treatment with Azstarys, the children’s total average sleep disturbance score on the Children’s Sleep Habits Questionnaire (CSHQ) decreased significantly from a mean of 53.4 points to 50.5 points. Furthermore their total mean CSHQ scores remained between 48.9 to 50.1 points for up to 12 months, indicating that the improvements in their sleep were sustained.The results of the study were presented in a poster at the Psych Congress 2022 in New Orleans. FDA Reviews Two-Month Aripiprazole Injection for SchizophreniaIn September, Otsuka America Pharmaceutical Inc. and H. Lundbeck A/S announced that the FDA has accepted for review a New Drug Application (NDA) for aripiprazole two-month, long-acting injectable for the treatment of schizophrenia in adults and for maintenance monotherapy of bipolar I disorder in adults. The NDA is for a formulation designed to be administered via intramuscular injection in the gluteal muscle.The NDA is based on data from a clinical trial involving 266 patients who were randomized to receive either four 920 mg injections of aripiprazole two-month long-acting injectable or eight 400 mg injections of aripiprazole one-month depot. Plasma concentrations of aripiprazole were similar between both groups of patients, and the two-month injectable was well-tolerated and showed no safety concerns compared with the once-monthly injectable. ■ ISSUES NewArchived

Relationship of Prolactin Concentrations to Steady-State Plasma Concentrations of Aripiprazole in Patients With Schizophrenia.

Aripiprazole is regarded as the first-line antipsychotic medication. Long-term aripiprazole therapy can cause hypoprolactinemia, which may result from its activity as a dopamine agonist. However, there is little information on hypoprolactinemia and steady-state aripiprazole concentrations. The subjects included 66 male and 177 female patients diagnosed with schizophrenia who were treated with aripiprazole. The plasma concentrations of aripiprazole and dehydroaripiprazole and the plasma concentration of prolactin were measured using high-performance liquid chromatography and enzyme immunoassay, respectively. A prolactin concentration of <5 ng/mL was defined as hypoprolactinemia. Fifty-two of the 66 male patients (79%) and 58 of the 177 female patients (33%) had hypoprolactinemia. There were significant inverse correlations between plasma prolactin levels and plasma concentrations of aripiprazole (rs = -0.447, P < 0.001) and the active moiety (aripiprazole plus dehydroaripiprazole) (rs = -0.429, P < 0.001) in men. In women, significant inverse correlations were also found between plasma prolactin levels and plasma concentrations of aripiprazole (rs = -0.273, P < 0.01) and the active moiety (rs = -0.275, P < 0.01). These findings suggest that lower prolactin levels are, to some extent, associated with higher plasma drug concentrations in male and female patients with schizophrenia treated with aripiprazole.

Influence of CYP2D6 Phenotypes on the Pharmacokinetics of Aripiprazole and Dehydro-Aripiprazole Using a Physiologically Based Pharmacokinetic Approach.

Background and ObjectivesAripiprazole is an atypical antipsychotic drug that is metabolized by cytochrome P450 (CYP) 2D6 and CYP3A4, which mainly form its active metabolite dehydro-aripiprazole. Because of the genetic polymorphism of CYP2D6, plasma concentrations are highly variable between different phenotypes. In this study, phenotype-related physiologically based pharmacokinetic models were developed and evaluated to suggest phenotype-guided dose adjustments.MethodsPhysiologically based pharmacokinetic models for single dose (oral and orodispersible formulation), multiple dose, and steady-state condition were built using trial data from genotyped healthy volunteers. Based on evaluated models, dose adjustments were simulated to compensate for genetically caused differences.ResultsPhysiologically based pharmacokinetic models were able to accurately predict the pharmacokinetics of aripiprazole and dehydro-aripiprazole according to CYP2D6 phenotypes, illustrated by a minimal bias and a good precision. For single-dose administration, 92.5% (oral formulation) and 79.3% (orodispersible formulation) of the plasma concentrations of aripiprazole were within the 1.25-fold error range. In addition, physiologically based pharmacokinetic steady-state simulations demonstrate that the daily dose for poor metabolizer should be adjusted, resulting in a maximum recommended dose of 10 mg, but no adjustment is necessary for intermediate and ultra-rapid metabolizers.ConclusionsIn clinical practice, CYP2D6 genotyping in combination with therapeutic drug monitoring should be considered to personalize aripiprazole dosing, especially in CYP2D6 poor metabolizers, to ensure therapy effectiveness and safety.

Aripiprazole Lauroxil Dosing Regimens: Understanding Dosage Strengths and Injection Intervals.

Aripiprazole lauroxil (AL) is a long-acting atypical antipsychotic approved for the treatment of schizophrenia in adults. AL has five regimen options that offer three different injection intervals using four different dosage strengths. The relationship between dosage strength (milligram injected), injection interval (time between injection visits), and expected steady-state plasma aripiprazole concentrations may not be readily apparent. This article illustrates the relationship by providing visual scenarios of steady-state plasma aripiprazole concentrations for the five AL regimens. The efficacy of AL was originally demonstrated in a pivotal study of two AL regimens (approved as 441mg monthly and 882mg monthly). The three additional regimens (662mg monthly, 882mg every 6weeks, and 1064mg every 2months) were approved based on pharmacokinetic bridging studies and population pharmacokinetic models. For this paper, expected steady-state concentrations for each AL regimen were derived from the published population pharmacokinetic models and compared using median values and ranges. The five labeled AL regimens differ in dosage strength and injection interval; however, model-simulated concentrations illustrate that each regimen produces steady-state plasma aripiprazole concentrations within the upper and lower bounds associated with known efficacy for AL 441mg and 882mg administered monthly. This visual presentation of the relationship between dosage strength of the AL injection, the interval between successive injections, and steady-state aripiprazole plasma concentrations may demonstrate for clinicians how dosage strength and injection interval can be considered in selecting the AL regimen option that best fits the clinical circumstances of the individual patient.

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.

Validated LC–MS/MS Method for Simultaneous Determination of Aripiprazole and its Three Metabolites in Human Plasma

Aripiprazole, a partial agonist of dopamine D2 receptors, is primarily metabolized to active dehydroaripiprazole and then converted to its urinary metabolites 1-(2,3-dichlorophenyl) piperazine (DCPP) and 3,4-dihydro-7-(3′carboxy) propoxy-2(1H) quinolinone (DCPQ). This study aimed to develop a simultaneous determination method for aripiprazole and its three metabolites in human plasma using isocratic liquid chromatography coupled to tandem mass spectrometry and then to apply it to pharmacokinetic analyses. The pretreatments for human plasma involve protein precipitation using acetonitrile under basic conditions. Aripiprazole and its metabolites were separated on an octadecylsilyl column filled with 3-µm particles using an isocratic mixture of 30% acetonitrile containing 0.1% formic acid with a total run time of 10 min. The mass spectrometer was run in the positive ion multiple reaction monitoring mode. The calibration curves were linear over the plasma concentration ranges 2–2000 ng mL−1 for aripiprazole, and 1–1000 ng mL−1 for dehydroaripiprazole, DCPP, and DCPQ. The lower limits of quantification in human plasma were 2 ng mL−1 for aripiprazole and 1 ng mL−1 for the metabolites. Their pretreatment recoveries were 88.3–102.7%. The intra-assay precision and accuracy were within 1.7–9.6 and 86.9–105.9% and inter-assay precision and accuracy were within 3.1–9.1 and 87.4–102.4%, respectively. The plasma concentrations of aripiprazole, dehydroaripiprazole, DCPP, and DCPQ ranged from 42.8 to 1369, 1.01–548, 1.02–46.1, and 1.69–475 ng mL−1, respectively, in 20 schizophrenia patients. In conclusion, this simultaneous determination method with acceptable analytical performance can be helpful for evaluating the pharmacokinetics of aripiprazole including the determination of its metabolites, in clinical research.

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

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

Plasma concentrations and dosing of 2 long-acting injectable formulations of aripiprazole.

Maintaining therapeutic plasma concentrations of an antipsychotic agent is essential in preventing relapse of symptoms in schizophrenia. Long-acting injectable (LAI) formulations provide extended exposure to antipsychotic therapy and have been useful in addressing treatment nonadherence. Aripiprazole is an atypical antipsychotic used in the treatment of schizophrenia and is available in 2 chemically different (aripiprazole monohydrate and aripiprazole lauroxil [AL]) and pharmaceutically different LAI formulations (aripiprazole once-monthly 400 mg [AOM 400] and AL). The pharmaceutical difference is that AL, unlike AOM 400, is a prodrug that requires additional metabolic steps to form the active drug aripiprazole. We present data demonstrating that aripiprazole plasma concentrations are similar for AOM 400 and the 882 mg dose of AL when administered once every 4 weeks and that both provide similar therapeutic plasma concentrations of aripiprazole when compared with therapeutic oral doses.

Serotonin syndrome with a combination of aripiprazole and fluoxetine: a case report.

Serotonin syndrome (SS) is a potentially life-threatening condition associated with increased serotonergic activity in the central nervous system. SS is characterized by a triad of altered mental status, autonomic dysfunction, and neuromuscular abnormalities [Boyer and Shannon, 2005]. The syndrome is, for some authors, a loose term to define the clinical picture at the moderate to severe end of a spectrum of serotonin toxicity, mild symptoms of which include tremor, hyperreflexia, and occasional myoclonus [Gillman and Whyte, 2004]. In the severe forms of toxicity, generalized myoclonus, sustained ankle clonus, and hyperreflexia may occur along with hyperthermia, which is associated with increased mortality [Gillman, 2013]. SS is classically associated with the high doses of a single selective serotonin reuptake inhibitor (SSRI) use, or with a combination of two or more serotonergic agents [Mason et al. 2000]. Fluoxetine is metabolized in the liver by the isoenzymes of the cytochrome P450 system, including CYP2D6 [Blazquez et al. 2012]. The role of CYP2D6 in the metabolism of fluoxetine may be clinically important, as there is a great genetic variability in the function of this enzyme [Gaedigk, 2013]. Aripiprazole, an atypical antipsychotic, which is a partial agonist at the 5-HT1A receptors, is equally metabolized via both CYP3A4 and CYP2D6 isoenzymes [Molden et al. 2006]. Therefore, coadministration with fluoxetine (a potent inhibitor of CYP450 2D6) may significantly increase the plasma concentrations of aripiprazole. On the other hand, aripiprazole has no known effect on fluoxetine metabolism [Boulton et al. 2010]. Here, we describe a case in which increased plasma concentration of aripiprazole due to a drug interaction with fluoxetine led to SS.

Lack of correlation between the steady-state plasma concentrations of aripiprazole and haloperidol in Japanese patients with schizophrenia.

Both aripiprazole and haloperidol have been used in the treatment of schizophrenia, and are metabolized by the cytochrome P450 (CYP) 2D6 and CYP3A4. The authors studied the correlations between the steady-state plasma concentrations (Css) of aripiprazole and its active metabolite, dehydroaripiprazole, and those of haloperidol in 19 Japanese patients with schizophrenia, together with the effects of CYP2D6 genotypes on the steady-state kinetics of these compounds. All the patients received first 24 mg/d of aripiprazole for 3 weeks and later received 6 mg/d of haloperidol for 2 weeks. Blood samplings were performed at least 2 weeks after the initiation of each treatment. The Css values of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass spectrometric detection, and those of haloperidol were measured by using an enzyme immunoassay. CYP2D6 genotypes were determined by using polymerase chain reaction analysis. None of the correlations between the Css of aripiprazole (r = 0.286) or the sum of aripiprazole plus dehydroaripiprazole (r = 0.344) and those of haloperidol were significant. The mean Css of aripiprazole was significantly higher (P < 0.05) in the subjects with 1 *10 allele of CYP2D6 (n = 6) than in those with no mutated alleles (n = 13), whereas there were no significant differences in those of haloperidol between the 2 groups. This study suggests that the Css of aripiprazole and that of aripiprazole plus dehydroaripiprazole do not correlate with that of haloperidol in the same individual, because of the greater involvement of CYP2D6 in the metabolism of aripiprazole than in that of haloperidol.

Effects of Genetic Polymorphisms of CYP2D6, CYP3A5, and ABCB1 on the Steady-State Plasma Concentrations of Aripiprazole and Its Active Metabolite, Dehydroaripiprazole, in Japanese Patients With Schizophrenia

We studied the effects of various factors, including genetic polymorphisms of the cytochrome P450 (CYP) 2D6, CYP3A5, and ABCB1, age, gender, and smoking habit on the steady-state plasma concentrations of aripiprazole and its active metabolite, dehydroaripiprazole, in 89 patients with schizophrenia (46 males, 43 females). All patients had been receiving fixed doses of aripiprazole for at least 2 weeks. The daily doses were 24 mg (n = 56) and 12 mg (n = 33). No other drugs except biperiden and flunitrazepam were coadministered. Plasma concentrations of aripiprazole and dehydroaripiprazole were measured using liquid chromatography with mass-spectrometric detection. The CYP2D6 (CYP2D6*5, CYP2D6*10, and CYP2D6*14), CYP3A5 (CYP3A5*3), and ABCB1 (C3435T and G2677T/A) genotypes were identified by PCR analyses. The mean concentration/dose ratios of aripiprazole and the sum of aripiprazole and dehydroaripiprazole were significantly higher in patients with 1 (P < 0.01 and P < 0.01) or 2 (P < 0.001 and P < 0.05) mutated alleles for CYP2D6 than in those without mutated alleles. No differences were found in the values of dehydroaripiprazole among CYP2D6 genotypes. There were no differences in the values of aripiprazole, dehydroaripiprazole, and the sum of the 2 compounds among CYP3A5 or the 2 ABCB1 variants. Multiple regression analyses including these polymorphisms, age, gender, and smoking habit showed that only the number of mutated alleles for CYP2D6 was correlated with mean concentration/dose ratios of aripiprazole [standardized partial correlation coefficients (beta) = 0.420, P < 0.001] and the sum of the 2 compounds (standardized beta = 0.335, P < 0.01). The findings of this study suggest that CYP2D6 genotypes play an important role in controlling steady-state plasma concentrations of aripiprazole and the sum of aripiprazole and dehydroaripiprazole in Asian subjects, whereas CYP3A5 and ABCB1 genotypes seemed unlikely to have an impact.

Effect of valproate on the plasma concentrations of aripiprazole in bipolar patients

Objective. There is very limited documentation available on the effects of valproate co-medication on the pharmacokinetics of aripiprazole in a naturalistic setting. The aim of the present study was to investigate the effect of co-medication with valproate on serum concentrations of aripiprazole in bipolar disorder patients in a clinical setting. Method. Plasma samples of bipolar disorder patients (n = 69) on a stable dose of aripiprazole 20 mg/day were analyzed by a liquid chromatography-mass spectrometry method in a routine therapeutic drug monitoring setting. Therapeutic drug monitoring was done for the entire study group before and after valproate co-administration. Results. We observed a statistically significant difference between the aripiprazole monotherapy and aripiprazole-valproate combination with respect to total aripiprazole plasma levels (p < 0.01). However, no statistically significant differences were noted in aripiprazole levels between the first week and the second week of valproate co-administration. Conclusion. In conclusion, concurrent treatment with valproate resulted in changes in the total aripiprazole plasma levels by 23%. But a lower total aripiprazole concentration during co-medication with valproate, caused by protein binding displacement, is reported being clinically insignificant in previous studies. The results from these studies are important in order to clarify clinical safety and efficacy.