Effects of cytochrome P450 3A modulators ketoconazole and carbamazepine on quetiapine pharmacokinetics

Multiple Adverse Reactions Associated With the Use of Second-Generation Antipsychotics in People With Alzheimer's Disease: A Pharmacovigilance Analysis Based on the FDA Adverse Event Reporting System

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative condition leading to memory loss, cognitive impairment, and neuropsychiatric symptoms. Second-generation antipsychotics (SGAs) are commonly used to manage these neuropsychiatric symptoms, but their safety profile in patients with AD requires further investigation.

OBJECTIVE

The objective was to evaluate the safety of SGAs in patients with AD by analyzing adverse drug reactions (ADRs) using the US Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

This study conducted a comprehensive analysis of FAERS data from 2014 to 2023, focusing on ADRs in patients with AD treated with SGAs such as risperidone, quetiapine, olanzapine, clozapine, and aripiprazole. Descriptive, disproportionality, time, and dose analysis were performed using the Bayesian confidence propagation neural network, Weibull, and physiologically based pharmacokinetic model.

RESULTS

Out of 1289 patients with AD treated with SGAs, the most common ADRs involved the nervous system, gastrointestinal system, and cardiac disorders. Disproportionality analysis identified significant positive signals in cardiac, renal, and vascular systems. Quetiapine, risperidone, and olanzapine showed more positive signals compared with clozapine and aripiprazole. Time analysis indicated that cardiovascular ADRs occurred randomly, whereas renal ADRs increased with prolonged use. Dose analysis suggested that small doses of SGAs did not elevate the risk of multiple cardiac, renal, or vascular ADRs.

CONCLUSION AND RELEVANCE

The study underscores the importance of monitoring for ADRs, particularly in the cardiac and renal systems, when using SGAs in patients with AD. Future research incorporating more comprehensive clinical data is warranted to support safe and rational drug utilization.

Pharmacotherapy of carbamazepine-treated patient after bariatric surgery: a complex interplay between altered absorption and drug-drug interactions

Changes in absorption and bioavailability of drugs have been described after bariatric surgery, especially shortly after the procedure. When a significant drug-drug interaction also occurs, it is difficult to predict the final combined effect of the surgery and the interaction. In this article, we present a case report of a patient with chronic psychiatric poly-medication including carbamazepine, a strong cytochrome P450 3A4 (CYP3A4) inducer. Significant changes in serum drug concentrations were observed during the 6 months after the surgery, including increased levels of quetiapine and trazodone, that cannot be attributed to the post-surgical alteration of absorption from the gastrointestinal tract. The influence of fluctuating carbamazepine levels on concomitant medication seemed to outweigh the effect of reduced absorption after surgery. This report highlights the need for careful pre-surgical evaluation of the patient's pharmacotherapy and pre- and post-operative therapeutic drug monitoring to prevent destabilisation of chronic conditions.

Pharmacokinetic Prediction of Immediate- and Extended-Release Tablets for Patients with Liver Disease Using Whole Body Physiologically-Based Pharmacokinetic Modeling for the Antipsychotic Drug Quetiapine

Although quetiapine metabolism occurs extensively in the liver and careful dosing is recommended in patients with liver disease, there has been a paucity of pharmacometric studies to adjust the clinical dose of quetiapine according to liver-disease severity. This study aimed to establish a whole-body, physiologically-based pharmacokinetic (WB-PBPK) model to explain interindividual variability in quetiapine PK and quantitatively predict PK in patients with liver disease. The developed WB-PBPK model well described the PK characteristics of different quetiapine regimens in healthy populations. The PK predictions could also be applied to patients with schizophrenia (without significant differences from healthy subjects). For the same total dose of quetiapine, both immediate-release (IR) and extended-release (ER) tablets showed significantly increased exposure and decreased clearance in patients with liver disease compared to healthy subjects. The model showed that steady-state plasma quetiapine concentrations exceeded the usual therapeutic range after multiple doses of IR tablets 250 mg three times daily or ER tablets 800 mg once daily in patients with liver disease. Therefore, the doses of quetiapine IR or ER tablets could be reduced by 0.10-0.50 times depending on liver-disease severity, so that mean steady-state plasma concentrations could be positioned near the therapeutic range. WB-PBPK modeling for quetiapine enabled quantitative prediction of PK according to IR or ER formulation and liver-disease severity. The results of this study provide useful data for improving the therapeutic use of quetiapine by enabling dose selection based on formulation and liver-disease severity.

Acute Quetiapine Intoxication: Relationship Between Ingested Dose, Serum Concentration and Clinical Presentation-Structured Literature Review and Analysis

Over the past decade, quetiapine has become one of the most commonly used psychotropic drugs in acute intoxication events worldwide. A structured literature review and analysis were conducted to assess the relationship between the kinetic and dynamic profiles in acute quetiapine intoxication. The correlation between dose and peak serum concentration (cmax) was determined using Pearson's correlation coefficient. Binary logistic regression was used to evaluate dose and cmax as predictors of the most common clinical events, signs and symptoms. One hundred and thirty-four cases of acute quetiapine ingestion were included in the analysis, with a median ingested dose of 10 g and a median cmax of 4 mg/L. The typical half-life was estimated to be 16.5 h, significantly longer than at therapeutic doses. For the immediate-release formulation, a biphasic disposition could not be excluded. Dose and cmax demonstrated a weak but significant correlation (r = 0.256; N = 63; p = 0.043). Central nervous system depression and tachycardia were the most common clinical signs. Higher doses and concentrations increased the risk of severe intoxication and were good predictors of intubation, tachycardia, hypotension, QTc prolongation and seizures, but not QRS prolongation, arrhythmia, heart block, hypokalaemia or acidosis. The thresholds for dose and cmax that increased the risk for individual signs and symptoms varied widely. However, doses > 3 g or cmax > 2 mg/L can be considered as alert levels that represent a high risk for severe clinical course of acute quetiapine intoxication.

Pharmacokinetic interaction of quetiapine and lamotrigine - victim and perpetrator?

OBJECTIVE

We aimed to investigate the ambiguous findings of earlier research regarding the reduction of quetiapine plasma levels when combined with lamotrigine, most likely via UDP-glucuronosyltransferase induction by lamotrigine.

METHODS

One thousand one hundred and fifty samples, divided into four groups of patients receiving either quetiapine immediate- (IR) or extended-release (XR) without or in combination with lamotrigine were compared regarding absolute and dose-adjusted plasma concentrations. Furthermore, samples of intra-individual controls were analyzed.

RESULTS

Patients receiving quetiapine IR in combination with lamotrigine showed 31% lower plasma (p = 0.002) and 23% lower dose-adjusted plasma concentrations (p = 0.004) compared to those receiving IR monotherapy. The proportion of patients with quetiapine plasma concentrations below the lower limit of the therapeutic reference range was 50% and 30% in the combination group and in patients receiving monotherapy, respectively (p = 0.03). However, no significant differences regarding plasma concentration (p = 0.13) and dose-adjusted plasma concentration (p = 0.42) were observed in patients with combination vs. monotherapy with the XR formulation of quetiapine. In the intra-individual controls, no trends could be identified, possibly due to insufficient number of samples (p > 0.05).

CONCLUSIONS

The combination of quetiapine IR with lamotrigine is associated with significantly lower drug concentrations of quetiapine, potentially impacting quetiapine effectiveness. For quetiapine ER, a significant interaction is less likely.

Dose-dependent effect of lamotrigine on quetiapine serum concentration in patients using instant release tablets

PURPOSE

Lamotrigine was previously reported to reduce serum concentration of quetiapine. The aim of this study was to investigate whether lamotrigine dose or quetiapine formulation was of importance for the drug interaction.

METHODS

Patients combining lamotrigine with quetiapine (cases) were included retrospectively from a routine therapeutic drug monitoring (TDM) service, as were a control group of patients using quetiapine without any interacting drugs. The case and control groups were divided into groups using immediate release (IR) and extended release (XR) quetiapine. The case group was further split into high-dose (> 200 mg/day) and low-dose (≤ 200 mg/day) lamotrigine users. Quetiapine concentration-to-dose (C/D) ratio and metabolite-to-parent ratio (MPR) were compared between the control group and dose-separated case groups using ANOVA test and t-tests.

RESULTS

In total, 406 patients were included. The mean C/D ratio of IR quetiapine was 46% lower in the high-dose lamotrigine group compared with the control group (P < 0.001), while no interaction effect was present in the low dose lamotrigine group (P = 0.7). Regardless of lamotrigine dose, there was no difference in quetiapine C/D ratio for patients using the XR formulation (P = 0.4). The quetiapine MPR was unaffected regardless of formulation and lamotrigine dose (P ≥ 0.06).

CONCLUSION

The effect of lamotrigine in reducing quetiapine concentration is only significant for patients using quetiapine IR tablets who are treated with lamotrigine doses > 200 mg/day. Because of high variability in the interaction effect, TDM of quetiapine should be recommended during co-prescription of high-dose lamotrigine.

Interactions between antiepileptic drugs and direct oral anticoagulants for primary and secondary stroke prevention

INTRODUCTION

Direct oral anticoagulants (DOAC) are the guideline-recommended therapy for prevention of stroke in atrial fibrillation (AF) and venous thromboembolism. Since approximately 10% of patients using antiepileptic drugs (AED) also receive DOAC, aim of this review is to summarize data about drug-drug interactions (DDI) of DOAC with AED by using data from PubMed until December 2023.

AREAS COVERED

Of 49 AED, only 16 have been investigated regarding DDI with DOAC by case reports or observational studies. No increased risk for stroke was reported only for topiramate, zonisamide, pregabalin, and gabapentin, whereas for the remaining 12 AED conflicting results regarding the risk for stroke and bleeding were found. Further 16 AED have the potential for pharmacodynamic or pharmacokinetic DDI, but no data regarding DOAC are available. For the remaining 17 AED it is unknown if they have DDI with DOAC.

EXPERT OPINION

Knowledge about pharmacokinetic and pharmacodynamic DDI of AED and DOAC is limited and frequently restricted to in vitro and in vivo findings. Since no data about DDI with DOAC are available for 67% of AED and an increasing number of patients have a combined medication of DOAC and AED, there is an urgent need for research on this topic.

The impact of CYP3A5*3 on oral quetiapine: A population pharmacokinetic model in Chinese bipolar disorder patients

BACKGROUND

There is great interindividual difference in the plasma concentration of quetiapine, and optimizing quetiapine therapy to achieve a balance between efficacy and safety is still a challenge. In our study, a population pharmacokinetic (PPK) model considering genetic information was developed with the expectation of comprehensively explaining this observation in Chinese patients with bipolar disorder.

METHODS

Patients who were dispensed quetiapine and underwent the therapeutic drug monitoring (TDM) were included. The genotypes of CYP3A5*3, CYP2D6*10, and ABCB1 C3435T/G2677T were analyzed. Finally, a multivariable linear regression model was applied to describe the PPK of quetiapine considering the covariates weight, height and genotype information.

RESULTS

A total of 175 TDM points from 107 patients were adopted for PPK model development. Resultantly, the CL/F of quetiapine in CYP3A5 expressers was 81.1 CL/h, whereas it was 43.6 CL/h in CYP3A5 nonexpressers. The interindividual variability in CL/F was 47.7 %. However, neither the ABCB1 nor CYP2D6 genotype was significantly associated with the predictor of quetiapine clearance in our study.

LIMITATIONS

Only trough concentrations were collected, and the span between different points was relatively wide, impeding the application of the typical nonlinear compartment model for PPK analysis. In addition, this was a single-center study which limited the sample of wild-type CYP3A5 carriers.

CONCLUSIONS

The currently established PPK model of quetiapine considering the contribution of the CYP3A5 genotype could efficiently predict the population and individual pharmacokinetic parameters of Chinese bipolar disorder patients, which could better guide the personalized therapy with quetiapine, thus to achieve the best clinical response.

The extent of cytochrome P450 3A induction by antiseizure medications: A systematic review and network meta-analysis

OBJECTIVE

Antiseizure medications (ASMs) are commonly categorized as enzyme-inducers and non-enzyme-inducers based on their propensity to enhance the metabolism of concomitantly administered drugs. This systematic review and network meta-analysis aimed to rank ASMs as cytochrome P450 3A (CYP3A)-inducers based on a comparative assessment of ASM-induced reduction in the concentrations of sensitive substrate drugs.

METHODS

The protocol was registered with PROSPERO (International Prospective Register of Systematic Reviews; CRD42022335846), and the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) standards were followed. We searched MEDLINE, Embase, and Cochrane until March 14, 2023 without an initial date restriction. Data were additionally obtained via the US Food and Drug Administration database. Studies had to be prospective, with ASM monotherapy for ≥5 days. The primary parameter was the magnitude of change in the area under the concentration-time curve of CYP3A substrates following treatment with the ASM. The standardized mean difference (SMD) was used as the point estimate for the indirect comparisons between ASMs using the pairwise method. Bias risk was assessed using the PKclin tool.

RESULTS

We identified 14 open-label, fixed-sequence studies with 370 participants. The effect size of 600 mg/day carbamazepine did not differ from those of 300 mg/day phenytoin (SMD = -.06, 95% confidence interval [CI] = -.18 to .07) and 200 mg/day cenobamate (SMD = -.11, 95% CI = -.26 to .04). Carbamazepine at 600 mg/day was the strongest CYP3A-inducer (P-score = .88), followed by carbamazepine 400 mg/day (.83), phenytoin 300 mg/day (.79), and cenobamate 200 mg/day (.73). Eslicarbazepine (800 mg/day) ranked higher than cenobamate 100 mg/day and oxcarbazepine 900 mg/day (.60, .39, and .37, respectively).

SIGNIFICANCE

Despite the limited number of studies, our network meta-analysis emphasizes that the magnitude of ASM effects on CYP3A substrate metabolism is a dose-dependent continuum. When possible, ASM classification as inducers should apply cutoff values tailored to the outcome. Prescribers should monitor plasma concentrations or clinical effects of CYP3A substrates and consider selecting concomitant medications accordingly.

Insights into the population pharmacokinetics and pharmacodynamics of quetiapine: a systematic review

INTRODUCTION

Quetiapine exhibits notable pharmacokinetic and pharmacodynamic (PK/PD) variability, the origins of which are poorly understood. This systematic review summarizes published population PK/PD studies and identifies significant covariates accounting for this variability to inform precision dosing.

METHODS

We systematically searched the PubMed, Web of Science, and Embase databases and compared study characteristics, model parameters, and covariate effects. Visual predictive distributions were used to compare different models. Forest plots and Monte Carlo simulations were used to assess the influence of covariates.

RESULTS

Six population PK and three population PK/PD studies were included. The median apparent clearance in adults was 87.7 L/h. Strong and moderate cytochrome P450 3A4 inducers increased the apparent clearance approximately fourfold, while strong cytochrome P450 3A4 inhibitors reduced it by 93%. The half-maximum effect concentrations were 82.8 ng/mL for the Brief Psychiatric Rating Scale and 583 ng/mL for dopamine D2 receptor occupancy. Both treatment duration and quetiapine exposure were associated with weight gain.

CONCLUSIONS

Concurrent administration of potent or moderate CYP3A4 inducers and inhibitors need to be avoided in quetiapine-treated patients. When co-medication is required, it is recommended to adjust the dosage based on therapeutic drug monitoring. Additional research is warranted to delineate the dose-exposure-response relationships of quetiapine and active metabolite norquetiapine in pediatrics, geriatrics, hepatically-impaired patients, and women using contraceptives or are pregnant or menopausal.

PROSPERO REGISTRATION

CRD42023446654.

Patterns of psychotropic drug use in veterans with epilepsy: Do drug interactions matter?

RATIONALE

Patients with epilepsy are likely to suffer from psychiatric comorbidities, including depression and anxiety. They often require treatment with multiple psychotropic drugs (PDs). While it is clear that CYP-inducing ASMs (EIASMs) can increase the oral clearance of multiple medications (thus lowering systemic exposure), it is less clear that all PK interactions are clinically meaningful (e.g. lower efficacy). As a first step in addressing this issue, this study sought to quantify the potential impact of ASM choice, whether EIASM or non-inducer (NIASM), on surrogate markers of suggestive of clinical use, including resultant antidepressant (AD) or antipsychotic (AP) dose, frequency of combination use of AD & AP, and number of multiple drug switches of PDs. Our hypothesis is that because of PK interactions, EIAED treatment would be associated with higher psychotropic drug doses, more frequent Rx adjustments and poly psychotropic comedication, all in order to optimize therapeutic response.

METHODS

Using VA pharmacy and national encounter databases, veterans with epilepsy were identified based on having a seizure diagnosis and being prescribed concomitantly an ASM and a psychotropic drug for at least 365 days between 10/1/2010 and 9/30/2014. Patients for whom psychotropic drugs were prescribed any time between beginning and end prescriptions dates of ASMs were considered. Among those, patients receiving both an EIASM + NEIASM concomitantly were categorized with the EIASM group. Patients were evaluated for AD only, AP only and both (AD & AP). To compute average drug doses per day, averages for each patient were computed and averaged again. Multiple drug switches were defined to be for patients who had been prescribed more than three psychotropic drugs during the observation period. Pearson's Chi-Square test was used to compare relative proportions of AD, AP and AD + AP in both groups.

RESULTS

In all, 16,188 patients were identified (57.0% on EIASM, 43.0% on NIASM) with a mean age of 58.7 years (91.2% male). A larger proportion of patients on EIASM received mono treatment with any psychotropic drug, as compared to NIASM (42.0% vs 36.1%). Among all, 59.6% received AD only, 6.5% received AP only, and 33.8% received both concurrently. Of EIASM, 62.5% were on AD, 5.9% on AP, and 31.7% on both AP & AD. For NIASM, 55.9% received AD, 7.4% AP, and 36.7% on AD & AP.Chi-square showed that the distribution of PD was statistically different between EIASM and NIASM groups. Z tests showed that each difference (AD, AP and both) in proportions was statistically significant (p values (4 tests, one Chi-square, 3 Z tests <0.001) between EIASM vs NIASM. Interestingly, mean doses of AD or AP did not appear to differ between ASM groups.

CONCLUSIONS

Concurrent psychotropic drug use is quite common in the VA population with epilepsy, and a large number of patients still receive enzyme-inducing ASMs that may complicate other medical therapies. Interestingly, in seeming contradiction to our hypothesis, mean daily doses of either AD or AP did not appear to differ between inducers vs non-inducers. Similarly, use of polytherapy, and/or multiple trials of various psychotropic drugs did not appear increased in the CYP-induced group. In fact, combination therapy of AD + AP was higher in NIASM than EIASM. These data suggest that perhaps these types of PK interactions may not in fact result in meaningful clinical differences. Since the present analyses did not include clinical psychiatric measures, future analyses examining direct clinical outcomes are clearly warranted.

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.

Relationship between serum concentration and clinical response of quetiapine in adolescents and adults with bipolar disorders in acute stage: a prospective observational study

BACKGROUND

It is found that there are great differences in the efficacy of quetiapine at the same dose in many patients with bipolar disorders. Therefore, therapeutic drug monitoring (TDM) is a valuable tool for guiding treatment with quetiapine. The aims of this study were to assess the relationship between serum concentration and clinical response of quetiapine in adolescents and adults with bipolar disorders in acute stage.

METHODS

The study design was prospective and observational. Within the naturalistic setting of a routine TDM service at the First Affiliated Hospital, Zhejiang University School of Medicine. Psychiatric symptoms were assessed using the HAMD (Hamilton Depression Scale), YRMS (Young manic rating scale) and CUDOS-M (Clinically Useful Depression Outcome Scale-Mixed Subscale). The decline of HAMD and YMRS scores was were used to assess clinical outcome of bipolar disorders respectively.

RESULTS

169 inpatients (23.7 % male, 76.3 % female) were enrolled in the study. We found that there was a strong correlation between quetiapine serum concentrations and clinical outcomes (r_s = 0.702, p < 0.001). While, quetiapine daily dose was not correlated with clinical outcome. We found that when the quetiapine serum level is >146.85 ng/ml in depression episodes patients could obtain a satisfactory treatment effect after 2 weeks of hospitalization.

CONCLUSIONS

We found a significant positive relationship between serum concentration and clinical outcome, and also determined the serum concentration of quetiapine for the treatment of bipolar depression.

The Impact of N-nitrosamine Impurities on Clinical Drug Development

Over the past few years, an increasing number of commercially available drugs have been reported to contain N-nitrosamine impurities above acceptable intake limits. Consequent interruption or discontinuation of the manufacturing and distribution of several marketed drugs has culminated into shortages of marketed drugs, including the antidiabetic drug metformin and the potentially life-saving drug rifampin for the treatment of tuberculosis. Alarmingly, the clinical development of new investigational products has been complicated as well by the presence of N-nitrosamine impurities in batches of marketed drug. In particular, rifampin is a key clinical index drug employed in drug-drug interaction (DDI) studies, and as a result of nitrosamine impurities regulatory bodies no longer accept the administration of rifampin in DDI studies involving healthy subjects. Drug developers are now forced to look at alternative approaches for commonly employed perpetrators, which will be discussed in this review.

Pharmacokinetic Interactions Between Antiseizure and Psychiatric Medications

Antiseizure medications and drugs for psychiatric diseases are frequently used in combination. In this context, pharmacokinetic interactions between these drugs may occur. The vast majority of these interactions are primarily observed at a metabolic level and result from changes in the activity of the cytochrome P450 (CYP). Carbamazepine, phenytoin, and barbiturates induce the oxidative biotransformation and can consequently reduce the plasma concentrations of tricyclic antidepressants, many typical and atypical antipsychotics and some benzodiazepines. Newer antiseizure medications show a lower potential for clinically relevant interactions with drugs for psychiatric disease. The pharmacokinetics of many antiseizure medications is not influenced by antipsychotics and anxiolytics, while some newer antidepressants, namely fluoxetine, fluvoxamine and viloxazine, may inhibit CYP enzymes leading to increased serum concentrations of some antiseizure medications, including phenytoin and carbamazepine. Clinically relevant pharmacokinetic interactions may be anticipated by knowledge of CYP enzymes involved in the biotransformation of individual medications and of the influence of the specific comedication on the activity of these CYP enzymes. As a general rule, these interactions can be managed by careful evaluation of clinical response and, when indicated, individualized dosage adjustments guided by measurement of drugs serum concentrations, especially if pharmacokinetic interactions may cause any change in seizure control or signs of toxicity. Further studies are required to improve predictions of pharmacokinetic interactions between antiseizure medications and drugs for psychiatric diseases providing practical helps for clinicians in the clinical setting.

Management of drug-drug interactions with nirmatrelvir/ritonavir in patients treated for Covid-19: Guidelines from the French Society of Pharmacology and Therapeutics (SFPT)

Objectives

Nirmatrelvir in association with ritonavir (PAXLOVID™, Pfizer) is an antiviral agent targeting the 3-chymotrypsin–like cysteine protease enzyme (3C-like protease or Mpro) which is a key enzyme of the viral cycle of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This combination with a well-known pharmacokinetic enhancer leads to a high risk for drug-drug interactions in a polymedicated elected population for treatment. The aim of this work was to provide recommendations on behalf of the national French society of pharmacology (French Society of Pharmacology and Therapeutics; SFPT), by suggesting optimal and pragmatic therapeutic strategies if nirmatrelvir/ritonavir is to be given together with drugs commonly used, in order to ensure secured physicians’ prescription.

Methods

Six clinical pharmacologists search the scientific literature to provide a first draft of recommendations. Thereafter, twelve other clinical pharmacologists verified the recommendations and proposed modifications. The final draft was then validated by all 18 participants.

Results

Five distinct recommendations were issued: i) contra-indications, ii) “PAXLOVID™ not recommended with the comedication”, iii) “PAXLOVID™ possible whether the comedication is discontinued”, iv) “PAXLOVID™ possible only after an expert advice” and v) “PAXLOVID™ possible without modification of the associated treatment”. The final document comprises recommendations for 171 drugs/therapeutic classes aiming to secure prescription. In complex situations, clinicians are advised to contact their pharmacology department to obtain specific recommendations on the management of drug-drug interactions with nirmatrelvir/ritonavir.

Conclusion

These recommendations intend to be a help for clinicians willing to prescribe nirmatrelvir/ritonavir and to prevent drug-drug interactions leading to adverse drug reactions or loss of efficacy. They constitute a guideline for primary care situations. Of course, some complex situations may require expert advices and here, again, clinical pharmacologists are at the forefront in providing therapeutic advice.

Alternatives to rifampicin: A review and perspectives on the choice of strong CYP3A inducers for clinical drug-drug interaction studies

N-Nitrosamine (NA) impurities are considered genotoxic and have gained attention due to the recall of several marketed drug products associated with higher-than-permitted limits of these impurities. Rifampicin is an index inducer of multiple cytochrome P450s (CYPs) including CYP2B6, 2C8, 2C9, 2C19, and 3A4/5 and an inhibitor of OATP1B transporters (single dose). Hence, rifampicin is used extensively in clinical studies to assess drug-drug interactions (DDIs). Despite NA impurities being reported in rifampicin and rifapentine above the acceptable limits, these critical anti-infective drugs are available for therapeutic use considering their benefit-risk profile. Reports of NA impurities in rifampicin products have created uncertainty around using rifampicin in clinical DDI studies, especially in healthy volunteers. Hence, a systematic investigation through a literature search was performed to determine possible alternative index inducer(s) to rifampicin. The available strong CYP3A inducers were selected from the University of Washington DDI Database and their in vivo DDI potential assessed using the data from clinical DDI studies with sensitive CYP3A substrates. To propose potential alternative CYP3A inducers, factors including lack of genotoxic potential, adequate safety, feasibility of multiple dose administration to healthy volunteers, and robust in vivo evidence of induction of CYP3A were considered. Based on the qualifying criteria, carbamazepine, phenytoin, and lumacaftor were identified to be the most promising alternatives to rifampicin for conducting CYP3A induction DDI studies. Strengths and limitations of the proposed alternative CYP3A inducers, the magnitude of in vivo CYP3A induction, appropriate study designs for each alternative inducer, and future perspectives are presented in this paper.

Comparison of serum and whole blood concentrations in quetiapine overdose cases

This study aimed to compare whole blood and serum concentrations of quetiapine in acute poisoning cases. Authentic whole blood and respective serum samples were routinely collected from patients diagnosed with blood poisoning at our University Hospital. Accordingly, whole blood and serum paired samples from nine patients (one male and eight female patients) were analyzed for quetiapine using liquid chromatography-mass spectrometry (LC-MS). Quetiapine concentrations in whole blood and serum samples ranged widely from 5.4 to 2780 ng/mL and 9.9 to 2500 ng/mL, respectively. The whole blood/serum concentration ratio was 0.5-1.1 and increased together with an increase in whole blood and serum quetiapine concentrations. The ratio was reversed at around 2500 ng/mL to > 1. Our findings suggest that whole blood concentrations are more useful than serum concentrations in diagnosing quetiapine poisonings.

Neutrophil Myeloperoxidase-Mediated N-Demethylation of Quetiapine Leads to N-Desalkylquetiapine, a Pharmacologically Active Cytochrome P450 Metabolite

The atypical antipsychotic drugs, quetiapine and clozapine, are associated with idiosyncratic drug reactions (such as agranulocytosis or neutropenia) that are thought to involve reactive metabolites. Neutrophil myeloperoxidase (MPO) metabolism of quetiapine is not well-studied, but is metabolized by cytochrome P450. Based on structural similarity to clozapine, we hypothesized that quetiapine can be metabolized by MPO and that there is overlap between cytochrome P450 and MPO metabolism of quetiapine. The interaction of quetiapine and clozapine with MPO and MPO chlorination activity was studied using UV-vis spectrophotometry. The metabolites were characterized using liquid chromatography-mass spectrometry (LC-MS), and electron paramagnetic resonance (EPR) spectroscopy was used for detecting drug-catalyzed glutathione oxidation. In the presence of quetiapine, MPO compound II accumulated for about 7.5 min, whereas in the presence of clozapine, MPO compound II was not observed as it was rapidly reduced back to the resting state. Increasing quetiapine concentrations resulted in a decrease in MPO chlorination activity, while the opposite result was found in the case of clozapine. UV-vis spectral studies showed no change when quetiapine was oxidized in the absence and presence of chloride anion (Cl^-, to catalyze chlorination reactions). Significant changes, however, were observed in the same assay with clozapine, where Cl^- appeared to hinder the rate of clozapine metabolism. The MPO-catalyzed hydroxylated and dealkylated metabolites of quetiapine and hydroxylated metabolites of clozapine were observed from the LC-MS analyses, particularly when Cl^- was included in the reaction. In addition, hydroxylated, dealkylated, and a proposed sulfoxide metabolite of quetiapine were also observed in the reaction catalyzed by human microsomes/NADPH. Lastly, compared to quetiapine, clozapine metabolism by MPO/H₂O₂ and glutathione produced more glutathionyl radicals using EPR spin trapping. In conclusion, MPO/H₂O₂/Cl^- was shown to metabolize quetiapine to S-oxidation and P450-like dealkylation products, and quetiapine metabolites were generally less reactive than clozapine.

Pharmacokinetics of caffeine self-administered in overdose in a Japanese patient admitted to hospital

Background

Caffeine (0.1 g) is used as a central nervous system stimulant and as a nontoxic phenotyping probe for cytochrome P450 1A2. However, an increasing number of suicide attempts by caffeine overdose have been recently reported.

Case presentation

A 25-year-old woman (body weight, 43 kg) who intentionally took an overdose of 5.9 g caffeine as a suicide attempt was emergently admitted to Kyoto Medical Center. The plasma concentrations of caffeine and its primary metabolite, N-demethylated paraxanthine, in the current case were 100 and 7.3 μg/mL, 81 and 9.9 μg/mL, 63 and 12 μg/mL, and 21 and 14 μg/mL, at 12, 20, 30, and 56 h after oral overdose, respectively. The observed apparent terminal elimination half-life of caffeine during days 1 and 2 of hospitalization was 27 h, which is several times longer than the reported normal value. This finding implied nonlinearity of caffeine pharmacokinetics over such a wide dose range, which could affect the accuracy of values simulated by a simplified physiologically based pharmacokinetic model founded on a normal dose of 100 mg. Low serum potassium levels (2.9 and 3.5 mM) on days 1 and 2 may have been caused by the caffeine overdose in the current case.

Conclusions

The patient underwent infusion with bicarbonate Ringer’s solution and potassium chloride and was discharged on the third day of hospitalization despite taking a potentially lethal dose of caffeine. The virtual plasma exposures of caffeine estimated using the current simplified PBPK model were higher than the measured values. The present results based on drug monitoring data and additional pharmacokinetic predictions could serve as a useful guide in cases of caffeine overdose.

Severe Adverse Drug Reactions to Quetiapine in Two Patients Carrying CYP2D6*4 Variants: A Case Report

We report two cases of patients who developed severe adverse drug reactions including persistent movement disorders, nausea, and vertigo during treatment with quetiapine at maximum daily doses ranging between 300 and 400 mg. The extensive hepatic metabolism of quetiapine is mainly attributed to cytochrome P450 3A4 (CYP3A4). However, there is recent evidence supporting the idea of CYP2D6 playing a role in the clearance of the quetiapine active metabolite norquetiapine. Interestingly, both patients we are reporting of are carriers of the CYP2D6*4 variant, predicting an intermediate metabolizer phenotype. Additionally, co-medication with a known CYP2D6 inhibitor and renal impairment might have further affected quetiapine pharmacokinetics. The herein reported cases could spark a discussion on the potential impact of a patient's pharmacogenetic predisposition in the treatment with quetiapine. However, further studies are warranted to promote the adoption of pharmacogenetic testing for the prevention of drug-induced toxicities associated with quetiapine.

Pharmacokinetics of duloxetine self-administered in overdose with quetiapine and other antipsychotic drugs in a Japanese patient admitted to hospital

Background

Combinations of antidepressant duloxetine (at doses of 40–60 mg/day) and other antipsychotics are frequently used in clinical treatment; however, several fatal and nonfatal cases of duloxetine overdose have been documented. We experienced a patient who had taken an overdose of duloxetine (780 mg) in combination with other drugs in a suicide attempt.

Case presentation

The patient was a 37-year-old man (body weight, 64 kg) with a history of gender identity disorder and depression. He intentionally took an overdose of duloxetine in combination with three other antipsychotic drugs (18 mg flunitrazepam, 850 mg quetiapine, and 1100 mg trazodone) and was emergently admitted to Kyoto Medical Center. The patient’s plasma concentration of duloxetine during ambulance transport was 57 ng/ml, and the level was still as high as 126 ng/mL at 32 h after administration. Duloxetine disappeared most slowly from plasma, in contrast to quetiapine, which was the fastest to clear among the four medicines determined in this patient. The observed concentrations of duloxetine in this overdose patient were generally within the 95% confidence intervals of the plasma concentration curves predicted using a physiologically based pharmacokinetic (PBPK) model.

Conclusion

Even if more than 1 h (the generally recommended period) has passed after administration of duloxetine in such overdose cases, gastric lavage and/or administration of activated charcoal may be effective in clinical practice up to 6 h because of the typically slow elimination behavior illustrated by the PBPK model. Pharmacokinetic profiles visualized using PBPK modeling can inform treatment decisions in cases of drug overdose for medicines such as duloxetine in emergency clinical practice.

Clinically Relevant Interactions between Atypical Antipsychotics and Anti-Infective Agents

This is a comprehensive review of the literature on drug interactions (DIs) between atypical antipsychotics and anti-infective agents that focuses on those DIs with the potential to be clinically relevant and classifies them as pharmacokinetic (PK) or pharmacodynamic (PD) DIs. PubMed searches were conducted for each of the atypical antipsychotics and most commonly used anti-infective agents (13 atypical antipsychotics by 61 anti-infective agents/classes leading to 793 individual searches). Additional relevant articles were obtained from citations and from prior review articles written by the authors. Based on prior DI articles and our current understanding of PK and PD mechanism, we developed tables with practical recommendations for clinicians for: antibiotic DIs, antitubercular DIs, antifungal DIs, antiviral DIs, and other anti-infective DIs. Another table reflects that in clinical practice, DIs between atypical antipsychotics and anti-infective agents occur in patients also suffering an infection that may also influence the PK and PD mechanisms of both drugs (the atypical antipsychotic and the anti-infective agent(s)). These tables reflect the currently available literature and our current knowledge of the field and will need to be updated as new DI information becomes available.

A Comprehensive Review on Importance and Quantitation of Atypical Antipsychotic Drugs and their Active Metabolites in Commercial Dosage Forms

Background:

Schizophrenia is a severe mental illness that affects more than twenty-one million people throughout the world. Schizophrenia also causes early death. Schizophrenia and other related psychotic ailments are controlled by the prescription of antipsychotic drugs, which act by blocking certain chemical receptors in the brain and thus relieves the symptoms of psychotic disorder. These drugs are present in the different dosage forms in the market and provided in a certain amount as per the need of the patients.

Objective:

Since such medications treat mental disorders, it is very important to have a perfect and accurate dose so that the risk factor is not affected by a higher or lower dose, which is not sufficient for the treatment. For accurate assay of these kinds of drugs, different analytical methods were developed ranging from older spectrophotometric techniques to latest hyphenated methods.

Results:

The current review highlights the role of different analytical techniques that were employed in the determination and identification of antipsychotic drugs and their metabolites. Techniques such as spectrophotometry, fluorimetry, liquid chromatography, liquid chromatography-mass spectrometry, gas chromatography, and gas chromatography-mass spectrometry employed in the method development of such antipsychotic drugs were reported in the review. Different metabolites, identified using the hyphenated techniques, were also mentioned in the review. The synthesis pathways of few of the metabolites were mentioned.

Conclusion:

The review summarizes the analyses of different antipsychotic drugs and their metabolites. A brief introduction of illnesses and their symptoms and possible medications were highlighted. Synthesis pathways of the associated metabolites were also mentioned.

Impact of quercetin on pharmacokinetics of quetiapine: insights from in-vivo studies in wistar rats

Quercetin (QCN) is commonly used in high doses as a dietary supplement for weight loss. Psychotic patients are at greater risk of developing obesity than the general population. The present study was designed to understand the impact of QCN on the exposure of quetiapine (QTE), an anti-psychotic drug with narrow therapeutic index and brain penetrating capability. The content of QTE in rat plasma was analyzed through liquid chromatography-tandem mass spectrometry. The results showed a significant (p < 0.05) increase in exposure of QTE (peroral dosed) in the animals pre-treated with QCN as compared to the control group. All the animals pre-treated with QCN, succumbed to death within 3-5 min of intravenous dosing of QTE (1 mg/kg). The studies in rat liver S9 fraction indicated that QCN could increase the metabolic stability of QTE by inhibiting the activity of CYP enzymes. The brain to plasma ratio of QTE increased upon QCN pre-treatment (2.6 vs 7.7), which could be attributed to P-glycoprotein inhibition at the blood-brain barrier by QCN. The current set of studies indicated that serious herb-drug interaction between QCN and QTE might occur when they are co-administered. Caution is advised for concomitant use of QCN rich dietary supplements with QTE.

Prevalence and sort of pharmacokinetic drug-drug interactions in hospitalized psychiatric patients

Psychiatric patients are high-risk patients for the development of pharmacokinetic drug-drug interactions (DDIs), leading to highly variable (victim) drug serum concentrations. Avoiding and targeting high-risk drug combinations could reduce preventable adverse drug reactions (ADRs). Pharmacokinetic cytochrome P450 (CYP)-mediated DDIs are often predictable and, therefore, preventable. The retrospective, longitudinal analysis used informations from a large pharmacovigilance study (Optimization of pharmacological treatment in hospitalized psychiatric patients study, study number 01VSF16009, 01/2017), conducted in 10 psychiatric hospitals in Germany. Medication data were examined for the co-prescription of clinically relevant CYP inhibitors or inducers and substrates of these enzymes (victim drugs). In total, data from 27,396 patient cases (45.6% female) with a mean (mean ± standard deviation (SD)) age of 47.3 ± 18.3 years were available for analysis. CYP inhibitors or inducers were at least once prescribed in 14.4% (n = 3946) of the cases. The most frequently prescribed CYP inhibitors were melperone (n = 2504, 28.1%) and duloxetine (n = 1324, 14.9%). Overall, 51.0% of the cases taking melperone were combined with a victim drug (n = 1288). Carbamazepine was the most frequently prescribed CYP inducer (n = 733, 88.8%). Combinations with victim drugs were detected for 58% (n = 427) of cases on medication with carbamazepine. Finally, a DDI was detected in 43.6% of the cases in which a CYP inhibitor or inducer was prescribed. The frequency of CYP-mediated DDI is considerably high in the psychiatric setting. Physicians should be aware of the CYP inhibitory and inducing potential of psychotropic and internistic drugs (especially, melperone).

Quetiapine dose optimisation during gestation: a pharmacokinetic modelling study

Objectives

The second-generation antipsychotic quetiapine has been demonstrated to undergo gestation-related changes in pharmacokinetics. This study applied pharmacokinetic modelling principles to investigate the mechanism of these changes and to propose new dosing strategies to counteract these changes.

Methods

A pharmacokinetic modelling approach was implemented using virtual population groups. Changes in quetiapine trough plasma concentration during gestation were quantified across all trimesters, and dose adjustment strategies were applied to counteract these changes by targeting a therapeutic range of 50–500 ng/ml throughout gestation.

Key findings

The application of the model during gestation predicted a decrease in trough concentration. A maximum decrease of 58% was predicted during trimester 2, and being associated with a statistically significant decrease in oral clearance at gestation week 25, 204 l/h ± 100.8 l/h compared with non-pregnant subjects, 121.9 l/h ± 51.8 l/h. A dosing optimisation strategy identified that dose increases to 500–700 mg twice daily would result in 32–55% of subjects possessing trough concentration in excess of 50 ng/ml.

Conclusions

Quetiapine doses in pregnancy should be increased to 500–700 mg twice daily to counteract a concomitant increase in metabolic clearance, increase in volume of distribution and decrease in plasma protein binding.

Interactions of cobicistat and ritonavir in patients with HIV and its clinical consequences

INTRODUCTION

The prescription of antiretroviral treatment (ART) that contains pharmacokinetic enhancers such as ritonavir and cobicistat is frequent. The objective of this stdy was to analyze the potential interactions of ART that include these molecules in their formulation with the patient's home medication, as well as the clinical management of those potentially serious.

METHODS

Prospective study conducted in the pharmacy care clinic of a third level hospital between January and December of 2018. Those HIV+patients with an ART containing cobicistat or ritonavir were included in the study. Potential interactions between ART and concomitant medication were analysed in three databases (Micromedex®, Drugs.com and Liverpool), the interventions carried out were detailed, and adverse drug reactions analysed.

RESULTS

968 patients were included with a total of 2,148 prescriptions (274 different medications). A total of 86 interventions were performed regarding potential interactions in patients. The most frequent were substitutions of corticoid treatments, treatment suspensions and closer monitoring of treatments. A total of possible adverse drug reactions were analysed. The degree of agreement in the severity classification of the interactions for cobicistat and ritonavir was good among the three databases. It was remarkable Micromedex® as the most complete because it has more registered medications.

CONCLUSION

The interactions between ART with pharmacokinetic enhancers in its composition and concomitant medication is frequent and requires a significant variety of interventions. The check of interactions in different databases is recommended since they can cause adverse drug reactions.

Delirium Induced by Quetiapine and the Potential Role of Norquetiapine

Quetiapine in an atypical antipsychotic drug that is frequently used for delirium and behavioral and psychological symptoms in dementia. However, its potential anticholinergic effects, mediated primarily through its metabolite norquetiapine, could present as counterproductive adverse effects in these situations. There is little data published discussing this potential negative impact on quetiapine’s safety and tolerability, especially in the elderly. Here, we present what is, to our knowledge, the first published case report of delirium apparently induced by low-dose quetiapine, in a 95-year-old patient with no prior history of mental illness, and the potential role of its metabolite norquetiapine.

Comparative omics analyses of hepatotoxicity induced by oral azole drugs in mice liver and primary hepatocytes

Ketoconazole (KTZ) and itraconazole (ITZ) are antifungal agents that have a broad spectrum of activity against fungal pathogens. However, the therapeutic indications of many antifungal drugs, including those of the azole group, are restricted due to possible hepatotoxicity. We performed toxicogenomic analyses using in vivo and in vitro models to investigate the molecular mechanisms underlying the hepatotoxicity of two azole antifungal drugs. C57BL/6 male mice were treated daily with KTZ or ITZ, sacrificed at days 1 or 7, and the serum biochemistry and histopathology results showed that the KTZ-treated mice exhibited hepatotoxicity. Primary hepatocytes from C57BL/6 mice also exposed to KTZ or ITZ, and the cytotoxic effects of KTZ and ITZ were evaluated; KTZ exerted a greater cytotoxic effect than ITZ. The gene expression profiles in the livers of the 7-day-treated group and primary hepatocytes of the 24-h-treated group for both KTZ and ITZ were comparatively analyzed. Differentially expressed genes were selected based on the fold-changes and statistical significance, and the biological functions were analyzed using ingenuity pathways analysis. The results revealed that genes related to cholesterol synthesis were overexpressed in the liver in the KTZ-treated group, whereas expression of those related to acute phase injury was significantly altered in the ITZ-treated group. Causal gene analyses suggested that sterol regulatory element-binding transcription factors are key regulators that activate the transcription of target genes associated with the hepatotoxicity induced by oral KTZ. These findings enhance our understanding of the molecular mechanisms underlying the hepatotoxicity of azole drugs.

Progress in the Consideration of Possible Sex Differences in Drug Interaction Studies

Background:

Anecdotal evidence suggests that there may be sex differences in Drug-drug Interactions (DDI) involving specific drugs. Regulators have provided general guidance for the inclusion of females in clinical studies. Some clinical studies have reported sex differences in the Pharmacokinetics (PK) of CYP3A4 substrates, suggesting that DDI involving CYP3A4 substrates could potentially show sex differences.

Objective:

The aim of this review was to investigate whether recent prospective DDI studies have included both sexes and whether there was evidence for the presence or absence of sex differences with the DDIs.

Methods:

The relevant details from 156 drug interaction studies within 124 papers were extracted and evaluated.

Results:

Only eight studies (five papers) compared the outcome of the DDI between males and females. The majority of the studies had only male volunteers. Five studies had females only while 60 had males only, with 7.7% of the studies having an equal proportion of both sexes. Surprisingly, four studies did not specify the sex of the subjects.

:

Based on the limited number of studies comparing males and females, no specific trends or conclusions were evident. Sex differences in the interaction were reported between ketoconazole and midazolam as well as clarithromycin and midazolam. However, no sex difference was observed with the interaction between clarithromycin and triazolam or erythromycin and triazolam. No sex-related PK differences were observed with the interaction between ketoconazole and domperidone, although sex-related differences in QT prolongation were observed.

Conclusion:

This review has shown that only limited progress had been made with the inclusion of both sexes in DDI studies.

Fatal combination of mitragynine and quetiapine - a case report with discussion of a potential herb-drug interaction

Kratom is a plant with dose-dependent mixed stimulant and opioid properties whose pharmacologic characteristics and social impact continue to be described. The main active isolate of kratom is mitragynine, an indole-containing alkaloid with opioid-like effects. Kratom toxicity and kratom-associated fatalities have been described, including those in association with additional drugs. In this paper we describe the case of a 27-year-old man who was found deceased with a toxic blood concentration of quetiapine in conjunction with the qualitative presence of mitragynine. Investigative and autopsy findings suggested perimortem hyperthermia and seizure-like activity. Kratom toxicity and kratom-associated fatalities are being increasingly reported. Experiments with kratom extracts have shown inhibitory effects upon hepatic CYP enzymes, leading to previous speculation of the potential for clinically significant interactions between kratom and a wide array of medications. Herein is described a fatal case of quetiapine toxicity complicated by mitragynine use. The potential ability of mitragynine to alter the pharmacokinetics of a prescription medication via inhibition of its hepatic metabolism is discussed.

High Doses of Drugs Extensively Metabolized by CYP3A4 Were Needed to Reach Therapeutic Concentrations in Two Patients Taking Inducers

INTRODUCTION

In the last 20 years of clinical practice, the senior author has identified these 2 rare cases in which the patients needed extremely high doses of drugs metabolized by CYP3A4 to reach and maintain serum therapeutic concentrations.

METHODS

The high metabolic ability of these 2 patients was demonstrated by the low concentration-to-dose ratios (C/D ratios) of several drugs metabolized by CYP3A4.

RESULTS

Case 1 was characterized by a history of high carbamazepine doses (up to 2,000mg/day) and needed 170 mg/day of diazepam in 2 days to cooperate with dental cleaning. The high activity of the CYP3A4 isoenzyme was manifested by fast metabolism for quetiapine and diazepam, which took more than 1 year to normalize after the inducer, phenytoin, was stopped. Case 2 was also very sensitive to CYP3A4 inducers as indicated by very low C/D ratios for carbamazepine, risperidone and paliperidone. The carbamazepine (2,800 mg/day) and risperidone (20 mg/day) dosages for this second patient are the highest doses ever seen for these drugs by the senior author. Risperidone induction appeared to last for many months and metabolism was definitively normal 3 years after stopping carbamazepine. On the other hand, olanzapine C/D ratios were normal for induction.

CONCLUSIONS

The literature has never described similar cases of very high doses of drugs metabolized by CYP3A4. We speculate that these 2 patients may have unusual genetic profiles at the nuclear receptor levels; these receptors regulate induction of drugs.

A rapid LC-MS/MS method for simultaneous determination of quetiapine and duloxetine in rat plasma and its application to pharmacokinetic interaction study

Combinations of new antidepressants like duloxetine and second-generation antipsychotics like quetiapine are used in clinical treatment of major depressive disorder, as well as in forensic toxicology scenarios. The drug–drug interaction (DDI) between quetiapine and duloxetine is worthy of attention to avoid unnecessary adverse effects. However, no pharmacokinetic DDI studies of quetiapine and duloxetine have been reported. In the present study, a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of quetiapine and duloxetine in rat plasma. A one-step protein precipitation with acetonitrile was applied for sample preparation. The analytes were eluted on an Eclipse XDB-C₁₈ column using the mixture of acetonitrile and 2 mM ammonium formate containing 0.1% formic acid at a gradient elution within 6.0 min. Quantification was performed in multiple-reaction-monitoring mode with the ion transitions m/z 384.4 → 253.2 for quetiapine, m/z 298.1→154.1 for duloxetine and m/z 376.2→165.2 for IS (haloperidol), respectively. Good linearity was obtained in the range of 0.50–100 ng/mL for quetiapine (r² = 0.9972) and 1.00–200 ng/mL for duloxetine (r² = 0.9982) using 50 μL of rat plasma, respectively. The method was fully validated with accuracy, precision, matrix effects, recovery and stability. The validated data have met the acceptance criteria in FDA guideline. The method was applied to a pharmacokinetic interaction study and the results indicated that quetiapine had significant effect on the enhanced plasma exposure of duloxetine in rats under combination use. This study could be readily applied in therapeutic drug monitoring of major depressive disorder patients receiving such drug combinations.

Analysis of Clinical Drug-Drug Interaction Data To Predict Magnitudes of Uncharacterized Interactions between Antiretroviral Drugs and Comedications

Despite their high potential for drug-drug interactions (DDI), clinical DDI studies of antiretroviral drugs (ARVs) are often lacking, because the full range of potential interactions cannot feasibly or pragmatically be studied, with some high-risk DDI studies also being ethically difficult to undertake. Thus, a robust method to screen and to predict the likelihood of DDIs is required. We developed a method to predict DDIs based on two parameters: the degree of metabolism by specific enzymes, such as CYP3A, and the strength of an inhibitor or inducer. These parameters were derived from existing studies utilizing paradigm substrates, inducers, and inhibitors of CYP3A to assess the predictive performance of this method by verifying predicted magnitudes of changes in drug exposure against clinical DDI studies involving ARVs. The derived parameters were consistent with the FDA classification of sensitive CYP3A substrates and the strength of CYP3A inhibitors and inducers. Characterized DDI magnitudes (n = 68) between ARVs and comedications were successfully quantified, meaning 53%, 85%, and 98% of the predictions were within 1.25-fold (0.80 to 1.25), 1.5-fold (0.66 to 1.48), and 2-fold (0.66 to 1.94) of the observed clinical data. In addition, the method identifies CYP3A substrates likely to be highly or, conversely, minimally impacted by CYP3A inhibitors or inducers, thus categorizing the magnitude of DDIs. The developed effective and robust method has the potential to support a more rational identification of dose adjustment to overcome DDIs, being particularly relevant in an HIV setting, given the treatment's complexity, high DDI risk, and limited guidance on the management of DDIs.

Effect of ABCB1 C3435T Polymorphism on Pharmacokinetics of Antipsychotics and Antidepressants

P-glycoprotein, encoded by ABCB1, is an ATP-dependent drug efflux pump which exports substances outside the cell. Some studies described connections between C3435T polymorphism T allele and lower P-glycoprotein expression; therefore, homozygous T/T could show higher plasma levels. Our aim was to evaluate the effect of C3435T on pharmacokinetics of 4 antipsychotics (olanzapine, quetiapine, risperidone and aripiprazole) and 4 antidepressants (trazodone, sertraline, agomelatine and citalopram). The study included 473 healthy volunteers receiving a single oral dose of one of these drugs, genotyped by real-time PCR. Multivariate analysis was performed to adjust the effect of sex and genotype of the main cytochrome P450 enzymes. C3435T polymorphism had an effect on olanzapine pharmacokinetics, as T/T individuals showed lower clearance and volume of distribution. T/T individuals showed lower T_1/2 of 9-OH-risperidone, but this difference disappeared after multivariate correction. T/T homozygous individuals showed lower dehydro-aripiprazole and trazodone area under the concentration-time curve, along with lower half-life and higher clearance of trazodone. C/T genotype was associated to higher citalopram maximum concentration. C3435T had no effect on quetiapine, sertraline or agomelatine pharmacokinetics. C3435T can affect the elimination of some drugs in different ways. Regarding risperidone, trazodone and dehydro-aripiprazole, we observed enhanced elimination while it was reduced in olanzapine and citalopram. However, in quetiapine, aripiprazole, sertraline and agomelatine, no changes were detected. These results suggest that P-glycoprotein polymorphisms could affect CNS drugs disposition, but the genetic factor that alters its activity is still unknown. This fact leads to consider the analysis of ABCB1 haplotypes instead of individual variants.

Effect of N-Desalkylquetiapine/Quetiapine Plasma Level Ratio on Anxiety and Depression in Bipolar Disorder: A Prospective Observational Study

BACKGROUND

The aim of this study was to analyze the relationships between quetiapine and N-desalkylquetiapine plasma levels and clinical improvement, particularly, in regard to depressive and anxious symptoms and to hostility.

METHODS

This was a prospective observational study that involved 37 outpatients diagnosed as having bipolar disorder I or II. All the patients were observed during a clinical acute and postacute phase. Patients were prescribed 50-800 mg of quetiapine. Patients were evaluated at baseline, after 15 days and after 3 months using the Brief Psychiatry Rating Scale with particular reference to the dimensions of depression, anxiety, and hostility. The plasma concentrations of quetiapine and N-desalkylquetiapine were determined after 3 months using blood samples taken at steady state.

RESULTS

There was a significant relationship between the N-desalkylquetiapine/quetiapine ratio and the improvement in the depression dimension, and there was not a significant relationship between the N-desalkylquetiapine/quetiapine ratio and anxiety and hostility improvement. Quetiapine treatment was well tolerated, and there were no extrapyramidal, anticholinergic, or other side effects to note. There was no relationship between plasma quetiapine or N-desalkylquetiapine concentrations and side effects.

CONCLUSIONS

Our findings confirm the efficacy of quetiapine on depressive symptoms, and the available data support that quetiapine's antidepressant activity is mediated by the active metabolite norquetiapine, and it exemplifies the case of an active metabolite that can make a drug like quetiapine originally introduced as an antipsychotic a useful antidepressant agent.

A liver-specific gene expression panel predicts the differentiation status of in vitro hepatocyte models

Alternative cell sources, such as three-dimensional organoids and induced pluripotent stem cell-derived cells, might provide a potentially effective approach for both drug development applications and clinical transplantation. For example, the development of cell sources for liver cell-based therapy has been increasingly needed, and liver transplantation is performed for the treatment for patients with severe end-stage liver disease. Differentiated liver cells and three-dimensional organoids are expected to provide new cell sources for tissue models and revolutionary clinical therapies. However, conventional experimental methods confirming the expression levels of liver-specific lineage markers cannot provide complete information regarding the differentiation status or degree of similarity between liver and differentiated cell sources. Therefore, in this study, to overcome several issues associated with the assessment of differentiated liver cells and organoids, we developed a liver-specific gene expression panel (LiGEP) algorithm that presents the degree of liver similarity as a "percentage." We demonstrated that the percentage calculated using the LiGEP algorithm was correlated with the developmental stages of in vivo liver tissues in mice, suggesting that LiGEP can correctly predict developmental stages. Moreover, three-dimensional cultured HepaRG cells and human pluripotent stem cell-derived hepatocyte-like cells showed liver similarity scores of 59.14% and 32%, respectively, although general liver-specific markers were detected.

CONCLUSION

Our study describes a quantitative and predictive model for differentiated samples, particularly liver-specific cells or organoids; and this model can be further expanded to various tissue-specific organoids; our LiGEP can provide useful information and insights regarding the differentiation status of in vitro liver models. (Hepatology 2017;66:1662-1674).

4β-Hydroxycholesterol level significantly correlates with steady-state serum concentration of the CYP3A4 substrate quetiapine in psychiatric patients

AIM

4β-Hydroxycholesterol (4βOHC) is sensitive towards induction or inhibition of CYP3A4, but its potential usefulness as a dosing biomarker remains to be demonstrated. The aim of this study was to investigate the correlation between 4βOHC levels and steady-state concentrations (Css) of quetiapine, a CYP3A4 substrate with high presystemic metabolism, in psychiatric patients.

METHODS

Serum samples from 151 patients treated with quetiapine as immediate release (IR; n = 98) or slow release (XR; n = 53) tablets were included for analysis of 4βOHC. In all patients, Css of quetiapine had been measured at trough level, i.e. 10-14 and 17-25 h post-dosing for IR and XR tablets, respectively. Correlations between 4βOHC levels and dose-adjusted Css (C/D ratios) of quetiapine were tested by univariate (Spearman's) and multivariate (multiple linear regression) analyses. Gender, age (≥60 vs. <60 years) and tablet formulation were included as potential covariates in the multivariate analysis.

RESULTS

Correlations between 4βOHC levels and quetiapine C/D ratios were highly significant both for IR- and XR-treated patients (P < 0.0001). Estimated Spearman r values were -0.47 (95% confidence interval -0.62, -0.30) and -0.56 (-0.72, -0.33), respectively. The relationship between 4βOHC level and quetiapine C/D ratio was also significant in the multiple linear regression analysis (P < 0.001), including gender (P = 0.023) and age (P = 0.003) as significant covariates.

CONCLUSIONS

The present study shows that 4βOHC level is significantly correlated with steady-state concentration of quetiapine. This supports the potential usefulness of 4βOHC as a phenotype biomarker for individualized dosing of quetiapine and other drugs where systemic exposure is mainly determined by CYP3A4 metabolism.

Development and validation of an HPLC-UV method for the simultaneous determination of the antipsychotics clozapine, olanzapine and quetiapine, several beta-blockers and their metabolites

A simple, accurate and selective column-switching high-performance liquid chromatography (HPLC) method was developed and validated for simultaneous quantification of six beta-blockers (metoprolol, timolol, bisoprolol, propranolol, carvedilol and nebivolol), three of their metabolites (α-hydroxy metoprolol, N-desisopropyl propranolol and 4'-hydroxy carvedilol 4-HCAR), three antipsychotics (olanzapine, clozapine and quetiapine) and three of their metabolites (N-desmethyl olanzapine, N-desmethyl clozapine and N-desalkyl quetiapine) in human serum. After pretreatment on a Merck LiChrospher RP-4 ADS column (25 μm), drugs were separated on a Phenomenex Gemini Phenyl Hexyl 110 A column (250 × 4.6 mm, 5 μm) using a gradient mixture of acetonitrile and potassium dihydrogen phosphate buffer pH 3.1 (containing 10% methanol) as a mobile phase at a flow rate of 1 mL/min. The total analysis time was 40 min. For detection of the analytes, four different UV wavelengths were used: 215, 226, 242 and 299 nm. The method was validated according to the guidelines of the Society of Toxicology and Forensic Chemistry in terms of selectivity, linearity, accuracy, precision and stability and successfully applied for the analysis of the 15 described analytes in human serum.

Comparative Physicochemical and Pharmacokinetic Properties of Quetiapine and Its Active Metabolite Norquetiapine

Quetiapine (QTP) is an atypical antipsychotic drug commonly used to treat several psychiatric disorders and is metabolized into the active metabolite norquetiapine (NQTP). This study was designed to evaluate and compare the physicochemical properties, metabolic stability, brain distribution, and pharmacokinetics of QTP and NQTP. Compared to QTP, NQTP had a higher pK_a, solubility, and rat liver microsomal stability, optimal log D and similar log P values. For pharmacokinetic evaluation, QTP and NQTP were administered orally and intravenously to rats at various doses. The plasma QTP and NQTP concentrations in rats were determined by a fully-validated liquid-chromatography tandem mass spectrometry (LC-MS/MS). Over the investigated dosing range, both QTP and NQTP showed linear pharmacokinetics. Following oral administration of the same dose, the area under the concentration-time curve (AUC_0-∞) and maximum serum concentration (C_max) were larger after NQTP administration compared to QTP administration. In addition, NQTP had a greater absolute oral bioavailability compared to QTP (15.6% vs. 0.63%, respectively). The brain-to-plasma concentration ratio was greater after NQTP administration compared to the QTP and NQTP ratios after QTP administration. NQTP administration results in increased systemic exposure and brain distribution compared to QTP administration. Future studies are needed to evaluate the pharmacologic and toxicologic effects of increased NQTP exposures.

Freeze Dried Quetiapine-Nicotinamide Binary Solid Dispersions: A New Strategy for Improving Physicochemical Properties and Ex Vivo Diffusion

Improving the physicochemical properties and oral bioavailability of quetiapine fumarate (QF) enabling enhanced antipsychotic attributes are the main aims of this research. The freeze dried solid dispersion strategy was adopted using nicotinamide (NIC) as highly soluble coformer. The prepared dispersions were characterized using scanning electron microscopy (SEM) differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Static disc intrinsic dissolution rate and ex vivo diffusion through intestinal tissues were conducted and compared to pure quetiapine fumarate. The results demonstrated a highly soluble coamorphous system formed between quetiapine fumarate and nicotinamide at 1 : 3 molar ratio through H-bonding interactions. The results showed >14-fold increase in solubility of QF from the prepared dispersions. Increased intrinsic dissolution rate (from 0.28 to 0.603 mg cm⁻² min⁻¹) and faster flux rate through duodenum (from 0.027 to 0.041 mg cm⁻² h⁻¹) and jejunum (0.027 to 0.036 mg cm⁻² h⁻¹) were obtained. The prepared coamorphous dispersion proved to be effective in improving the drug solubility and dissolution rate and ex vivo diffusion. Therefore, binary coamorphous dispersions could be a promising solution to modify the physicochemical properties, raise oral bioavailability, and change the biopharmaceutics classification (BCS) of some active pharmaceutical ingredients.