A systematic review and combined analysis of therapeutic drug monitoring studies for oral paliperidone

The impact of pregnancy on the pharmacokinetics of antiseizure medications: A systematic review and meta-analysis of data from 674 pregnancies

OBJECTIVE

Increasing evidence suggests that the physiological changes of pregnancy may impact pharmacokinetics of antiseizure medications (ASM), and this may affect treatment outcomes. The aim of this study was to quantify the pregnancy impact on the ASM pharmacokinetics.

METHODS

A systematic literature search was conducted in PubMed/EMBASE in November 2022 and updated in August 2023 for studies comparing levels of ASM in the same individuals during pregnancy and in the preconception/postpartum period. Alteration ratios between the 3rd trimester and baseline were estimated. We also performed a random-effects meta-analysis calculating between-timepoint differences in mean differences (MDs) and 95% confidence intervals (95%CIs) for dose-adjusted plasma concentrations (C/D ratios). Study quality was assessed using the ClinPK guidelines.

RESULTS

A total of 65 studies investigating 15 ASMs in 674 pregnancies were included. The largest differences were reported for lamotrigine, oxcarbazepine and levetiracetam (alteration ratio 0.42, range 0.07-2.45, 0.42, range 0.08-0.82 and 0.52, range 0.04-2.77 respectively): accordingly, C/D levels were lower in the 3rd trimester for lamotrigine, levetiracetam and the main oxcarbazepine metabolite monohydroxycarbazepine (MD = -12.33 × 10-3, 95%CI = -16.08 to -8.58 × 10-3 (μg/mL)/(mg/day), p < 0.001, MD = -7.16 (μg/mL)/(mg/day), 95%CI = -9.96 to -4.36, p < 0.001, and MD = -4.87 (μg/mL)/(mg/day), 95%CI = -9.39 to -0.35, p = 0.035, respectively), but not for oxcarbazepine (MD = 1.16 × 10-3 (μg/mL)/(mg/day), 95%CI = -2.55 to 0.24 × 10-3, p = 0.10). The quality of studies was acceptable with an average rating score of 11.5.

CONCLUSIONS

Data for lamotrigine, oxcarbazepine (and monohydroxycarbazepine) and levetiracetam demonstrate major changes in pharmacokinetics during pregnancy, suggesting the importance of therapeutic drug monitoring to assist clinicians in optimizing treatment outcomes.

How can we better address the pharmacokinetics of antipsychotics in children and adolescents?

INTRODUCTION

Despite a steady increase of antipsychotic prescriptions in children and adolescents, knowledge about pharmacokinetics and dosing of antipsychotics in children and adolescents remains limited.

AREAS COVERED

We discuss seven issues with major impact on the pharmacokinetics of antipsychotics in youth: estrogens, ii) obesity, iii) ethnicity, iv) smoking, v) inflammation, vi) drug-drug interactions (DDIs), and vii) pharmacogenetics. Despite their major impact, these issues have not been adequately considered in the context of dosing algorithms for antipsychotics in youth. A simple tool to quantify the impact of these pharmacokinetics issues on antipsychotics is therapeutic drug monitoring (TDM), which refers to the quantification of the prescribed medication in the blood of the patients, as a surrogate for the peripheral antipsychotic exposure. We also provide summary tables extrapolated from the adult literature on metabolism, therapeutic reference ranges (TRRs) and DDIs.

EXPERT OPINION

Despite considerable experience with TDM for antipsychotics in the management of other patient subgroups, TDM use for antipsychotics in children and adolescents may be limited with TRRs invariably being extrapolated from adult patients. Advancing TDM knowledge is expected to help clinicians address the special properties of pharmacokinetics of antipsychotics and ultimately enable antipsychotic dose individualization in youth.

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, specialized tools are used. Three tools have been proven useful to personalize 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 50 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 optimize treatment effects, minimize side effects and ultimately reduce the global burden of diseases, personalized drug treatment has not yet become the standard of care in psychiatry.

A Systematic Review of Clozapine Concentration-Dose Ratio from Therapeutic Drug Monitoring Studies in Children and Adolescents Treated with Clozapine for Mental Disorders

BACKGROUND

Therapeutic drug monitoring of clozapine in children and adolescents has received insufficient attention. Calculation of concentration-to-dose (C/D) ratios from trough steady-state concentrations estimate drug clearance.

METHODS

A systematic electronic literature search was conducted in 3 article databases from inception until January 10, 2023, and articles reporting clozapine concentrations in children and adolescents were retrieved. The pharmacokinetic quality of the studies was assessed, and clozapine C/D ratios were calculated using the sample mean clozapine dose and concentration.

RESULTS

Of the 37 articles of potential interest, only 7 reported clozapine trough and steady-state concentrations. After excluding case reports and a study confounded by fluvoxamine, 4 studies on psychosis from Europe and the United States were included. The clozapine C/D ratios were similar to published adult values and ranged from 0.82 to 1.24 with a weighted mean of 1.08 ng/mL per mg/d. The weighted means were 334 mg/d for the dose and 380 ng/mL for the concentration. The stratified analysis of the weighted mean clozapine C/D ratios from 2 studies showed lower values in 52 male (1.05 ng/mL per mg/d) than in 46 female (1.46 ng/mL per mg/d) children and adolescents, with values similar to those reported for European adult nonsmokers. Two female adolescents had high clozapine C/D ratios (2.54 ng/mL per mg/d), an Asian American patient with borderline obesity and a patient with intellectual disability with low dosage (mean = 102 mg/d) and concentration (mean = 55 ng/mL).

CONCLUSIONS

Reports on clozapine therapeutic drug monitoring in children and adolescents are limited in number and quality. Future studies should focus on basic pharmacokinetic issues, such as stratification by sex, smoking, and relevant comedications with inductive or inhibitory properties.

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.

Paliperidone-Associated Sialorrhea: A Case Report With Review of Current Literature

PURPOSE/BACKGROUND

Antipsychotic-associated sialorrhea is a problematic adverse effect with potentially negative consequences on quality of life and medication adherence. While clozapine is the antipsychotic that is most associated with sialorrhea, there have been published reports of other second-generation antipsychotics associated with sialorrhea, including aripiprazole, olanzapine, quetiapine, and risperidone. Although drooling is mentioned within the package insert for paliperidone, to date there have been minimal published reports in which paliperidone is implicated as the offending agent.

METHODS/PROCEDURES

Here, we present a case of sialorrhea in a 56-year-old man with schizoaffective disorder who had a supratherapeutic paliperidone level after both oral and intramuscular paliperidone use.

FINDINGS/RESULTS

Paliperidone was ultimately cross tapered to aripiprazole, and the patient was given atropine drops and benztropine with resolution of the sialorrhea. We provide a review of the literature regarding the other available reports of paliperidone-associated sialorrhea, possible mechanisms behind pathophysiology, as well as reports from the World Health Organization and Food and Drug Administration adverse event reporting systems.

IMPLICATIONS/CONCLUSIONS

Clinicians should be aware of the potential for paliperidone and other nonclozapine second-generation antipsychotics to be associated with sialorrhea, especially given the increased frequency of their use for a variety of psychiatric disorders.

Precision psychiatry: The complexity of personalizing antipsychotic dosing

Recently, Salagre and Vieta commented on the complexity of implementing precision medicine in psychiatry. For 25 years, this author has focused on a circumscribed type of precision medicine: personalized dosing using pharmacokinetic mechanisms to stratified patients. This short communication focuses on personalized dosing of three oral antipsychotics (clozapine, risperidone and paliperidone) and presents their maintenance dosing in a table which provides dose-correction factors generated by pharmacokinetic studies. Inhibitors need dose-correction factors < 1 and inducers need correction factors >1. Clozapine maintenance dosing is based on the dose needed to reach 350 ng/ml (the minimum plasma therapeutic concentration in treatment-resistant schizophrenia). Clozapine maintenance dosing is influenced by 3 levels of complexity: 1) ancestry groups (Asians/Native Americans; Europeans and Blacks), 2) sex-smoking subgroups (lowest dose in female non-smokers and highest in male smokers) and 3) presence/absence of poor metabolizer status (due to genetic and non-genetic causes including co-prescription of inhibitors, obesity or inflammation). Risperidone and paliperidone maintenance dosing are based on the dose needed to reach plasma concentrations of 20-60 ng/ml. Risperidone PMs need approximately half the dose, which can be explained by genetics (CYP2D6 PMs) or co-prescription of CYP2D6 inhibitors. Fluoxetine co-prescription may require one fourth the risperidone maintenance dose. Carbamazepine co-prescription may require twice the risperidone maintenance dose. Although not well studied, two groups may need higher doses of oral paliperidone: Koreans may need 1.5 times higher doses while those taking carbamazepine may need 3 times higher paliperidone maintenance doses. Precision dosing in psychiatry requires using blood levels of individuals.

Pharmacokinetic drug interactions with oral haloperidol in adults: dose correction factors from a combined weighted analysis

INTRODUCTION

Pharmacokinetic (PK) drug-drug interactions (DDIs) of oral haloperidol, a first-generation antipsychotic, are systematically reviewed.

AREAS COVERED

After exclusions, the search for DDIs with oral haloperidol provided 47 articles as victim and 7 as perpetrator. Changes in mean haloperidol concentration-to-dose (C/D) ratios after weighting each study's size were used to calculate the effects of other drugs (inhibitors/inducers) on haloperidol. These changes of haloperidol C/D ratio were used to estimate dose-correction factors (<1 for inhibitors and >1 for inducers).

EXPERT OPINION

A box summarizes our recommendations for clinicians regarding our current knowledge of haloperidol PK DDIs, which will need to be updated as new information becomes available. Moderate to strong inducers (carbamazepine, phenobarbital, phenytoin, or rifampin) should be avoided since they required dose-correction factors of 2-5. Smoking appeared to be a weak inducer (dose-correction factor 1.2). Fluvoxamine, promethazine, and combinations of CYP3A4 and CYP2D6 inhibitors should be avoided. There are no long-term studies on fluoxetine to provide a dose correction factor. Limited information suggests that valproate may be an inhibitor (dose-correction factor 0.6). In most patients, haloperidol may not have clinically relevant effects as a perpetrator, but in vitro and clinical studies suggest it is a weak CYP2D6 inhibitor.

Effects of body weight, smoking status, and sex on plasma concentrations of once-monthly paliperidone palmitate

OBJECTIVES

Knowledge about the impact of body composition features on pharmacokinetics of newer long-acting injectable antipsychotics is limited.

METHODS

We analyzed steady-state plasma concentrations of paliperidone in different body mass index (BMI), age, sex, and smoking status patient subgroups treated with once-monthly paliperidone palmitate (PP1M). Paliperidone plasma concentrations and dose-adjusted-plasma concentrations (C/D) from a therapeutic drug monitoring (TDM) database of PP1M-treated patients were compared among normal BMI, overweight, and obese patients as well as between females vs. males, elderly vs. non-elderly, and smokers vs. non-smokers using non-parametric tests.

RESULTS

In a total of 183 PP1M-treated patients, we found highly variable paliperidone plasma concentrations between individuals but no significant effect of PP1M dose or dosing intervals (p> 0.05). C/D ratios were similar in 54 obese, 82 overweight, and 47 normal BMI patients (p> 0.05). Females had 13.7% higher C/D ratios compared to males, yet this difference was not significant (p> 0.05). No differences were found between elderly vs. non-elderly patients or for smokers vs. non-smokers (p> 0.05).

CONCLUSION

Our findings suggest that age, sex, smoking, or body weight may not substantially affect pharmacokinetic indices of PP1M. The high interindividual variation of plasma concentrations implies that TDM may be helpful to enhance PP1M efficacy and tolerability.

Clinical response in patients treated with once-monthly paliperidone palmitate: analysis of a therapeutic drug monitoring (TDM) database

To investigate pharmacokinetic correlates of clinical response in patients treated with once-monthly paliperidone palmitate (PP1M) injections at steady state. Plasma concentrations and dose-adjusted-plasma concentrations (C/D) of paliperidone from a naturalistic therapeutic drug monitoring (TDM) database were compared between responders and non-responders using the Clinical Global Impressions-Improvement scale (CGI-I) ratings. Analyses were based on the non-parametric Mann-Whitney U test and the Pearson Chi-squared test (χ²) with a significance level of 0.05. Subgroup analyses were performed separately in patients with schizophrenia spectrum, schizoaffective disorders and bipolar disorders. Comparing 93 responders with 80 non-responders, we detected no significant differences in the proportion of females, age, and body mass index (p's ranging 0.18-0.83); there were more smokers in the group of non-responders (p = 0.04), which also included more patients with bipolar disorders (p = 0.014). Despite the lack of differences for prescribed PP1M doses and dose intervals (p = 0.42 and p = 0.11, respectively), non-responders had higher paliperidone plasma concentrations and C/D levels (p = 0.033 and p = 0.021, respectively). Subgroup analyses did not yield differences for paliperidone plasma and C/D levels between non-responders and responders with schizophrenia spectrum (p = 0.099 and p = 0.14, respectively) and bipolar disorders (p = 0.95 and p = 0.75, respectively); dose-adjusted plasma concentrations were higher in non-responders compared to responders with schizoaffective disorders (p = 0.039), while no differences were reported for plasma levels (p = 0. 15). Our results show that paliperidone plasma concentrations over injection doses may be associated with patterns of clinical response suggesting potential utility of TDM as part of PP1M-based maintenance treatment.

Severe and persistent mental illness (SPMI) in pregnancy and breastfeeding: focus on second-generation long acting injectable antipsychotics

Introduction: Pregnant women and fetuses are more likely than ever to be exposed to antipsychotic drugs (APs) during pregnancy and postpartum period. Second-generation APs (SGA) are increasingly used among women in reproductive age. Key outcomes (i.e., congenital malformations, pregnancy and maternal outcomes, neonatal/infant risks, and developmental/long-term outcomes) following the exposure to APs remain limited in number and size and yield of inconsistent findings overall, particularly regarding long-acting injectable AP (LAI-APs) formulations.Areas covered: The review aims at providing a summary of current knowledge on potential risks and safety profile of LAI-APs during pregnancy and breastfeeding, specifically focusing on SGA.Expert opinion: The management of safety and tolerability of long-acting injectable AP (LAI-APs) is far from having solid scientific evidence. In fact, due to ethical reasons, there is a lack of randomized clinical trials that limits the reliability and generalizability of the available data on LAI-APs safety profile during the perinatal period, being limited in the scientific literature only to isolated case reports. Therefore, it seems to be important for the future pathways to perinatal mental health care, providing a network of specialized clinicians and systematically collecting data of pregnant/puerperal women on oral and/or LAI APs-therapy about mother and infant outcomes.

Pharmacokinetic Correlates of Once-Monthly Paliperidone Palmitate-Related Adverse Drug Reactions

OBJECTIVE

The objective of this study was to investigate associations between pharmacokinetic correlates and once-monthly paliperidone palmitate (PP1M)-related adverse drug reactions (ADRs).

METHODS

Plasma concentrations and dose-adjusted plasma concentrations ('concentration-by-dose' [C/D]) of paliperidone from a naturalistic therapeutic drug monitoring database of PP1M-treated patients were compared between patients with ADRs, classified according to the Udvalg for Kliniske Undersogelser side-effect rating scales categories, and patients without ADRs. Analyses included non-parametric tests and a logistic regression model with a significance level set at 0.05.

RESULTS

In 172 patients, we found no differences in sex, age, smoking, body mass index, PP1M dose, paliperidone plasma concentrations, and C/D values (p > 0.05) between 44 patients with and 128 patients without PP1M-related ADRs. We did not detect differences when specifying for different types of ADRs (p > 0.05). Injection intervals were shorter in patients with vs patients without ADRs (p = 0.03). The logistic regression did not report effects for sex, plasma concentrations, or C/D values (p > 0.05). Post hoc analyses in male patients receiving PP1M every 28 weeks reported higher paliperidone concentrations and C/D values in patients with vs without ADRs (p = 0.049 and p = 0.022). Within the group of male patients, we found an odds ratio of 3.07 for PP1M-associated ADRs in patients with C/D values above 7.7 (ng/mL)/(mg/day).

CONCLUSIONS

Our findings did not reveal distinct patterns of paliperidone concentrations in patients with PP1M-related ADRs. However, male patients receiving PP1M every 28 days with C/D values higher than 7.7 (ng/mL)/(mg/day) showed a higher risk for ADRs, implying that therapeutic drug monitoring may be useful in assessing the risk of PP1M-related ADRs.

Detection of sivelestat and its metabolite in small volumes of plasma from Chinese ALI/ARDS patients with SIRS via high-throughput UPLC-MS/MS: A pharmacokinetic study

In this study, we developed a sensitive and efficient analytical approach combining a 96-well plate-based protein precipitation strategy with ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-MS/MS) in order to assess the pharmacokinetic (PK) properties of sivelestat and its metabolite XW-IMP-A in samples of plasma from ALI/ARDS patients with SIRS. The samples were separated via gradient elution with a C18 column (Phenomenex Kinetex, C18, 2.6 μm, 100 Å, 50 × 2.1 mm) using 0.1 % formic acid aqueous solution (A) and acetonitrile-methanol (1:1, V:V) (B) as a mobile phase at a 0.6 mL/min flow rate. UPLC-MS/MS spectra were generated in positive ion mode, and multiple reaction monitoring (MRM) was used to detect the following transitions: m/z 435.1 → 360.0 for sivelestat, m/z 469.0 → 394.0 for sivelestat-IS, m/z 351.0 → 276.0 for XW-IMP-A, and m/z 384.9 → 310.0 for XW-IMP-A-IS. This assay was run for 2.5 min in total, and achieved lowest limit of quantitation values of 2.0 ng/mL and 0.5 ng/mL for sivelestat and XW-IMP-A, respectively, while remaining highly linear from 2-500 ng/mL for sivelestat (r² ≥ 0.9900) and from 0.5-125 ng/mL for XW-IMP-A (r² ≥ 0.9900). These validated data were consistent with US Food and Drug Administration (FDA) and European Medicines Agency (EMA) acceptance criteria. In addition, this method was successfully applied to the steady-state PK evaluation of ALI/ARDS patients with SIRS.

Lack of Smoking Effects on Pharmacokinetics of Oral Paliperidone-analysis of a Naturalistic Therapeutic Drug Monitoring Sample

INTRODUCTION

Major smoking effects have been reported for a series of psychotropic agents, mainly including substrates of CYP450 1A2, although smoking may also affect alternative metabolic pathways. To our knowledge, smoking effects on paliperidone pharmacokinetics have not been assessed yet.

METHODS

We compared plasma concentrations of paliperidone as well as dose-corrected-plasma concentrations (C/D) from a naturalistic database between smokers and nonsmokers using nonparametrical tests, such as the Mann-Whitney U-test (MWU). Additionally, we compared light and heavy smokers with nonsmokers separately.

RESULTS

Comparing 55 smokers with 37 nonsmokers treated with oral paliperidone, no differences in the percentage of females, age, body weight, body mass index, and daily paliperidone dose were reported (p=0.709 for χ², p=0.26, p=0.38, p=0.67, and p=0.8 for MWU). No differences were detected in plasma concentrations or C/D values (p=0.50 and p=0.96 for MWU). Likewise, differences in daily dose, plasma concentrations, or C/D values were not significant between light smokers (n=17) and nonsmokers (p=0.61, p=0.81, and p=0.33 for MWU) or heavy smokers (n=22) and nonsmokers (p=0.874, p=0.38, and p=0.59; MWU in all cases).

DISCUSSION

Paliperidone is not affected by smoking, and paliperidone dose-adjustments in smokers may not be necessary. This may be seen as an essential difference to risperidone, whose cytochrome-mediated metabolism might be affected by smoking.

The impact of pregnancy on the pharmacokinetics of antidepressants: a systematic critical review and meta-analysis

Introduction: Pregnancy-related physiological changes exert a crucial impact on the pharmacokinetics of antidepressants; however, the current evidence presents inconsistencies. A clearer understanding of pregnancy-related effects on antidepressant disposition may facilitate the development of guidelines for appropriate dose adjustments during the course of pregnancy based on therapeutic drug monitoring.Areas covered: We systematically reviewed studies comparing antidepressant levels in the same individuals during pregnant and non-pregnant states. Using dose-adjusted plasma concentration measurements, we estimated alteration ratios between the 3rd trimester and baseline (before or after pregnancy). Additionally, we performed a meta-analysis for changes in dose-adjusted concentrations to estimate mean differences.Expert opinion: Data for several antidepressants display clear alteration patterns during pregnancy. On the basis of the alteration ratios trimipramine, fluvoxamine, and nortriptyline show a prominent decrease in dose-adjusted levels, especially in the 3rd trimester. Clomipramine, imipramine, citalopram, and paroxetine show smaller decreases in dose-adjusted concentrations in the third trimester. For escitalopram, venlafaxine and fluoxetine, changes are considered negligible. For sertraline, there was a tendency toward increased dose-adjusted concentrations in pregnancy. Available evidence suffers from major limitations and factors affecting pharmacokinetics have been insufficiently addressed. Further research is required to promote knowledge on pregnancy effects on antidepressant pharmacokinetics.

Monitoring and improving antipsychotic adherence in outpatient forensic diversion programs

Outpatient diversion programs present an opportunity for severely mentally ill defendants to receive psychiatric treatment and have alleged offenses dismissed by the court. Moreover, the successful completion of pretrial diversion is associated with fewer post-program arrest and jail days. The target patient population for such programs is typically people with schizophrenia spectrum disorders, but the care of such patients in outpatient settings presents challenges for monitoring treatment fidelity, specifically antipsychotic adherence, as low adherence rates are associated with increased rates of recidivism. Presented here is a review of evidence-based strategies that must be employed to track antipsychotic adherence in outpatient diversion programs, including pill counts, use of long-acting injectable antipsychotics, and determination of plasma antipsychotic levels to assess adherence and the adequacy of antipsychotic treatment. Antipsychotic therapy remains the foundation of schizophrenia treatment, but only through the use of all available modalities can clinicians maximize the odds that schizophrenia patients in pretrial diversion maintain psychiatric stability and successfully complete mental health court mandates.

A systematic review and combined meta-analysis of concentration of oral amisulpride

AIMS

Amisulpride, a first-line schizophrenia treatment, has shown large interindividual variability in plasma/serum levels, often outside the reference range (100-320 ng/mL). This study aims to clarify the impact of dose, sex, age and related factors for the interpatient variability in amisulpride plasma/serum concentration.

METHODS

Both English and Chinese databases were searched from their inception to May 16, 2019, using the terms: amisulpride and (plasma OR serum OR blood OR "drug monitoring" OR concentration). Studies reporting concentrations and either a dose, associated factor, clinical outcome or side effect were included.

RESULTS

Fourteen studies with 1628 participants were eventually included. Eligible articles yielded data on drug concentration and dose, averaging 333.9 (95% confidence interval [CI]: 294.5-373.3) ng/mL and 636.2 (95% CI: 549.7-722.6) mg/d, respectively. The calculated mean concentration-to-dose (C/D) ratio was 0.60 (95% CI: 0.52-0.67) (ng/mL)/mg. Subgroup analysis suggested that female patients on combined lithium-amisulpride have higher concentration levels and C/D ratios. Age was slight positive associated with C/D ratio while not for plasma level. Smoker patients have high concentration level than nonsmoking patients but not for C/D. Responsive and nonresponsive groups did not differ in concentration and C/D.

CONCLUSION

Pooled concentration levels of amisulpride were higher than recommended with wide individual variation, especially in older patients, female patients and patients taking amisulpride combined with lithium. The specific therapeutic reference range for amisulpride may require reconstruction, which should consider the influence of age, sex, kidney function, drug-drug interactions, different dose regimens and sampling times in future study.

Roux-en-Y Gastric Bypass and Antipsychotic Therapeutic Drug Monitoring: Two Cases

Many patients with psychiatric conditions undergo bariatric surgery. The Roux-en-Y gastric bypass (RYGB) procedure alters medication pharmacokinetic properties and may have significant impact on drug response. Our report is the first to describe atypical antipsychotic therapeutic drug monitoring in patients who have undergone RYGB. The first patient is a 53-year-old female with a stable psychiatric condition undergoing a laparoscopic RYGB. Her medications prior and following the procedure include bupropion, fluvoxamine, lurasidone, methylphenidate, oxcarbazepine, and verapamil. A concentration steady-state lurasidone concentration obtained prior to the procedure was 20 ng/mL and returned at 8.1 ng/mL, 29 days after surgery. The second patient is a 42-year-old female psychiatric inpatient who had previously undergone an RYGB procedure. Medications on admission included phenytoin, oxcarbazepine, risperidone, and venlafaxine. The patient was believed to be a good candidate for a long-acting antipsychotic and paliperidone was chosen. After concentration-steady-state on 6 mg oral paliperidone, a 23.5-hour trough level was drawn. The patient was noted to be improved on the oral paliperidone, the paliperidone long-acting injection was given, and the patient was discharged. After discharge, the paliperidone concentration returned very low at 1.1 ng/mL. We describe the contributions of drug-drug interactions, medication release mechanisms, and food coadministration that may have affected our therapeutic drug monitoring. Our therapeutic drug monitoring results need to be replicated prior to use in the general population but suggest that oral extended-release drug formulations are particularly poor choices and that nonoral antipsychotic formulations may be preferred in some patients who have undergone RYBG.

Self-Report for Measuring and Predicting Medication Adherence: Experts' Experience in Predicting Adherence in Stable Psychiatric Outpatients and in Pharmacokinetics

THE PROBLEM

Poor adherence to appropriately prescribed medication is a global challenge for psychiatrists.

PRIOR STUDIES

Measuring adherence is complicated. In our recent three-country naturalistic study including more than 1000 patients and their adherence to multiple medication prescriptions at the same time, patients' self-report of adherence to each specific drug was the only practical option for measuring adherence. Systematic literature reviews provide inconsistent results for sociodemographic, clinical and medication variables as predictors of adherence to psychiatric drugs. Our studies over the last 10 years in relatively stable psychiatric outpatients have shown that some self-reported health beliefs had consistent, strong effects and a better predictive role. Three dimensions of these health beliefs are characteristics of the individual: 1) attitudes toward psychiatric medication such as pharmacophobia (fear of taking drugs or medicines), 2) health locus of control (the belief patients have about who or what agent determines the state of their health), 3) psychological reactance (an emotional reaction in direct contradiction to rules or regulations that threaten or suppress certain freedoms in behavior). They can be measured by the Patient Health Beliefs Questionnaire on Psychiatric Treatment. The attitude toward each specific medication can be measured by the necessity-concern framework and summarized as the presence or absence of skepticism about that drug. After 25 years conducting pharmacokinetic studies in psychiatric drugs, particularly antipsychotics, we have limited understanding of how to use blood levels to predict the effects of non-adherence or to establish it.

EXPERT OPINION ON FUTURE STUDIES

Future studies to predict adherence should include the inpatient setting and explore insight. Studying the pharmacokinetics associated with non-adherence in each psychiatric drug is a major challenge. Medication adherence is a complex and dynamic process changing over time in the same patient. Personalizing adherence using psychological or pharmacological variables are in their initial stages.

Clinically Significant Drug-Drug Interactions with Agents for Attention-Deficit/Hyperactivity Disorder

This article provides an overview of the pharmacokinetic drug-drug interactions (DDIs) for agents prescribed for attention-deficit/hyperactivity disorder (ADHD). Polypharmacy in the treatment of patients with ADHD leads to high exposures to DDIs and possibly adverse safety outcomes. We performed a systematic search of DDI reports for ADHD agents in Embase and Medline. We also searched for agents in the pharmacological pipeline, which include (1) mazindol, molindone and viloxazine, which were previously prescribed for other indications; (2) centanafadine and AR-08, never before approved; and (3) two extracts (Polygala tenuifolia extract and the French maritime pine bark extracts). The identified literature included case reports, cross-sectional, cross-over and placebo-controlled studies of patient cohorts and healthy volunteers. The DDIs were classified as follows: ADHD agents acting as perpetrators, i.e., affecting the clearance of co-prescribed agents (victim drugs), or ADHD agents being the victim drugs, being affected by other agents. Ratios for changes in pharmacokinetic parameters before and after the DDI were used as a rough estimate of the extent of the DDI. Alcohol may increase plasma dextroamphetamine concentrations by presystemic effects. Until studies are done to orient clinicians regarding dosing changes, clinicians need to be aware of the potential for cytochrome P450 (CYP) 2D6 inhibitors to increase amphetamine levels, which is equivalent to increasing dosages. Atomoxetine is a wide therapeutic window drug. The CYP2D6 poor metabolizers who do not have CYP2D6 activity had better atomoxetine response, but also an increased risk of adverse effects. CYP2D6 inhibitors have been used to increase atomoxetine response in CYP2D6 extensive metabolizers. Guanfacine is mainly metabolized by CYP3A4, which can be induced and inhibited. The package insert recommends that in guanfacine-treated patients, after adding potent CYP3A4 inducers, the guanfacine dose should be doubled; after adding potent CYP3A4 inhibitors the guanfacine dose should be halved. Based on a phenobarbital case report and our experience with CYP3A4-metabolized antipsychotics, these correction factors may be too low. According to two case reports, carbamazepine is a clinically relevant inducer of methylphenidate (MPH). A case series study suggested that MPH may be associated with important elevations in imipramine concentrations. Due to the absence of or limitations in the data, no comments for clinicians can be provided on the pharmacokinetic DDIs for clonidine, centanafadine, mazindol, molindone, AR-08, P. tenuifolia extract and the French maritime pine bark extracts. According to currently available data, clinicians should not expect that ADHD drugs modify each other's serum concentrations. A summary table for clinicians provides our current recommendations on pharmacokinetic DDIs of ADHD agents based on our literature review and the package inserts; whenever it was possible, we provide information on serum concentrations and dose correction factors. There will be a need to periodically update these recommendations and these correction factors as new knowledge becomes available.

Paliperidone is associated with reduced risk of severe hepatic outcome in patients with schizophrenia and viral hepatitis: A nationwide population-based cohort study

OBJECTIVE

Paliperidone, a second-generation antipsychotic, has been found to have minimal hepatotoxicity in patients with schizophrenia. However, long-term hepatic outcome in patients with schizophrenia and viral hepatitis remains unclear.

METHODS

Data obtained from the Taiwan National Health Insurance Research Database was used to enroll newly diagnosed schizophrenic patients between January 2007 and December 2013. Patients with schizophrenia and viral hepatitis who were receiving paliperidone were allocated to the paliperidone group while those who were not receiving paliperidone were allocated to the control group. Using a 1:2 ratio, we matched the age, sex, and index year to select the control participants. Patients with severe hepatic outcomes (SHOs) before enrollment were excluded. The two groups were studied until December 31, 2013. The primary endpoint was the occurrence of SHOs including liver failure, liver decompensation, liver transplantation, or liver cancer.

RESULTS

We identified 134 patients with schizophrenia and viral hepatitis who received paliperidone and 268 matched patients who did not receive paliperidone. Of the 402 patients, 22 (5.47%) developed SHOs during a mean follow-up period of 3.57 ± 1.62 years, including 2 (1.49%) from the paliperidone cohort and 20 (7.46%) from the control group. Furthermore, the Cox multivariate proportional hazards analysis revealed that the risk decreased with paliperidone use (adjusted hazard ratio [HR]: 0.155, 95% confidence interval [CI]: 0.032-0.737, p = 0.019) after adjusted for confounding factors.

CONCLUSION

Paliperidone treatment was associated with a reduced risk of SHOs in patients with schizophrenia and viral hepatitis.

How to identify and manage non-response to clozapine?

Clozapine is the only approved treatment for Treatment-Refractory Schizophrenia. Here we describe a case series of three hospitalized patients with clozapine nonresponse. One of them responded to clozapine after dose adjustments were made for an interaction between clozapine and ciprofloxacin. The other two cases remained clozapine nonresponders despite optimizing clozapine treatment. However, both these patients responded to other antipsychotic medications (APMs) with better tolerability than observed with clozapine treatment. This case series focuses on diagnosing a genuine from a pseudo-nonresponse to clozapine and to consider other APMs in genuine nonresponse before switching to invasive interventions, such as ECT.

Personalizing dosing of risperidone, paliperidone and clozapine using therapeutic drug monitoring and pharmacogenetics

By combining knowledge of pharmacogenetics, therapeutic drug monitoring (TDM) and drug-drug interactions (DDIs) the author developed a model for personalizing antipsychotic dosing, which is applied to risperidone, 9-hydroxyrisperidone or paliperidone, and clozapine. Drugs are approved using an average dose for an ideal average patient, but pharmacologists have described outliers: genetic poor metabolizers (PMs) and ultrarapid metabolizers (UMs). Environmental and personal variables can also make patients behave as PMs or UMs. Drug clearance is represented by the concentration-to-dose (C/D) ratio under steady-state and trough conditions. A very low C/D ratio indicates a UM, while a very high C/D ratio indicates a PM. Total risperidone C/D ratio for the oral formulation is around 7 ng/ml per mg/day and can be influenced by CYP2D6 polymorphism, DDIs with inducers and inhibitors, and renal function. Oral paliperidone has low availability; its C/D ratio is around 4.1 ng/ml per mg/d and can be influenced by inducers and renal impairment. Once-a-month long-acting paliperidone provides a C/D ratio around 7.7 ng/ml per mg/day at steady state, which is expected to be in the 8th month (before the 9th injection). TDM is particularly important for long-acting paliperidone formulations that may accumulate once steady state is reached (after years for the 3- and 6-month formulations). In the US, clozapine C/D ratios typically range from 0.6 (male smokers) to 1.2 (female non-smokers) ng/ml per mg/day. East Asians' clozapine C/D ratios appear to be twice as high. Inhibitors (including fluvoxamine and oral contraceptives) and inflammation can also increase clozapine C/D ratios. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

Clozapine Metabolism in East Asians and Caucasians: A Pilot Exploration of the Prevalence of Poor Metabolizers and a Systematic Review

PURPOSE/BACKGROUND

In clozapine therapeutic drug monitoring (TDM) studies, Chinese reached the same concentrations using half the dosage Caucasians use. Defining clozapine poor metabolizers (PMs) requires stratification by ethnicity, smoking, and sex.

METHODS/PROCEDURES

After sex and smoking stratification in 129 Chinese inpatients (mean, 8.8 TDM samples per patient), we explored the association between the total concentration-dose (C/D) ratio and CYP1A2 (*1C, *1F, and *7) and CYP2C19 alleles (*2 and *3). A systematic literature review identified 22 clozapine TDM prior studies (13 in Caucasians and 7 in East Asians).

FINDINGS/RESULTS

In our Chinese sample, the mean total clozapine C/D ratio (ng/mL per mg/d) was 1.96 for 22 male smokers, 2.07 for 5 female smokers, 2.47 for 36 male nonsmokers, and 2.95 for 66 female nonsmokers. CYP1A2 *1C had no significant effects, and CYP1A2 *1F had small effects. Five clozapine PMs (4%) needed low clozapine doses of 75 to 115 mg/d to get therapeutic concentrations. Using the same methodology in a published Italian sample, we found 5 PMs (3.3% of 152). In the systematic review, the clozapine C/D ratio (ng/mL per mg/d) was higher when comparing: (1) weighted mean values of 1.57 in 876 East Asians versus 1.07 in 1147 Caucasians and (2) ranks of 8 East Asians versus 13 Caucasian samples (P < 0.001).

IMPLICATIONS/CONCLUSIONS

Future TDM studies need to further explore the frequency of clozapine PMs after sex and smoking stratification in East Asian and Caucasian patients. Compared with Caucasians, East Asians appear to have a clinically relevant decrease in clozapine clearance.

The current data on the 3-month paliperidone palmitate formulation for the treatment of schizophrenia

INTRODUCTION

A three-month injection of paliperidone palmitate (PP3M) has been gradually introduced in the market since 2015. Recently, and due to different reasons, there is an increase in the LAIAs prescription rates, including patients in early phases of psychotic disorders. Areas covered: The following article provides an overview of the antipsychotic market before providing the reader with an overview of the efficacy and tolerability data of the 3-month paliperidone palmitate formulation for the treatment of schizophrenia. The authors take into account the current state of knowledge, as well as the needs not covered by other therapeutic tools at our disposal at this time. Expert opinion: PP3M offers a substantially longer dosing interval than other options, which may be a potential advancement to reduce nonadherence in some patients. Future research, both from randomized controlled trials and large pragmatic studies in real-world settings, will identify which subpopulation and disease stages may obtain greater benefit from this new formulation.