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Albitar O, Harun SN, Sheikh Ghadzi SM. Semi-physiological Pharmacokinetic Model of Clozapine and Norclozapine in Healthy, Non-smoking Volunteers: The Impact of Race and Genetics. CNS Drugs 2024; 38:571-581. [PMID: 38836990 DOI: 10.1007/s40263-024-01092-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/17/2024] [Indexed: 06/06/2024]
Abstract
BACKGROUND AND OBJECTIVES: Clozapine is the medication of choice for treatment-resistant schizophrenia. However, it has a complex metabolism and unexplained interindividual variability. The current work aims to develop a pharmacokinetic model of clozapine and norclozapine in non-smokers and assess the impact of demographic and genetic predictors. METHODS Healthy volunteers were recruited in a population pharmacokinetic study. Blood samples were collected at 30 min and 1, 2, 3, 5 and 8 h following a single flat dose of clozapine (12.5 mg). The clozapine and norclozapine concentrations were measured via high-performance liquid chromatography-ultraviolet method. A semi-physiological pharmacokinetic model of clozapine and norclozapine was developed using nonlinear mixed-effects modeling. Clinical and genetic predictors were evaluated, including CYP1A2 (rs762551) and ABCB1 (rs2032582), using restriction fragment length polymorphism. RESULTS A total of 270 samples were collected from 33 participants. The data were best described using a two-compartment model for clozapine and a two-compartment model for norclozapine with first-order absorption and elimination and pre-systemic metabolism. The estimated (relative standard error) clearance of clozapine and norclozapine were 27 L h-1 (31.5 %) and 19.6 L h-1 (30%), respectively. Clozapine clearance was lower in sub-Saharan Africans (n = 4) and higher in Caucasians (n = 9) than Asians (n = 20). Participants with CYP1A2 (rs762551) (n = 18) and ABCB1 (rs2032582) (n = 12) mutant alleles had lower clozapine clearance in the univariate analysis. CONCLUSIONS This is the first study to develop a semi-physiological pharmacokinetic model of clozapine and norclozapine accounting for the pre-systemic metabolism. Asians required lower doses of clozapine as compared with Caucasians, while clozapine pharmacokinetics in sub-Saharan Africans should be further investigated in larger trials.
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Affiliation(s)
- Orwa Albitar
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM, 11800, Gelugor, Penang, Malaysia
- Roche Pharma Research and Early Development, Basel, Switzerland
| | - Sabariah Noor Harun
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM, 11800, Gelugor, Penang, Malaysia
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Mansour K, Fredj NB, Ammar H, Romdhane HB, Mhalla A, Chaabane A, Chadli Z, Aouam K. Exploring clozapine pharmacokinetics in Tunisian schizophrenic patients: A population-based modelling approach investigating the impact of genetic and non-genetic variables. Basic Clin Pharmacol Toxicol 2024; 134:805-817. [PMID: 38599832 DOI: 10.1111/bcpt.14009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 02/29/2024] [Accepted: 03/22/2024] [Indexed: 04/12/2024]
Abstract
Clozapine is characterized by a large within- and between-patient variability in its pharmacokinetics, attributed to non-genetic and genetic factors. A cross-sectional analysis of clozapine trough concentration (Clz C0) issued from Tunisian schizophrenic patients was collected and analysed using a nonparametric modelling approach. We assessed the impact of demographic covariates (age, weight and sex), patient's habits (smoking status, alcohol and caffeine intake) and the genetic factors (CYP1A2*1C, CYP1A2*1F and CYP2C19*2 polymorphisms) on each pharmacokinetic parameter. An external validation of this pharmacokinetic model using an independent data set was performed. Fit goodness between observed- and individual-predicted data was evaluated using the mean prediction error (% MPE), the mean absolute prediction error (% MAPE) as a measure of bias, and the root mean squared error (% RMSE) as a measure of precision. Sixty-three CLz C0 values issued from 51 schizophrenic patients were assessed in this study and divided into building and validation groups. CYP1A2*1F polymorphism and smoking status were the only covariates significantly associated with clozapine clearance. Precision parameters were as follows: 1.02%, 0.95% and 22.4%, respectively, for % MPE, % MAPE and % RMSE. We developed and validated an accurate pharmacokinetic model able to predict Clz C0 in Tunisian schizophrenic patients using the two parameters CYP1A2*1F polymorphism and smoking.
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Affiliation(s)
- Khadija Mansour
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Nadia Ben Fredj
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Helmi Ammar
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Haifa Ben Romdhane
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Ahmed Mhalla
- Department of Psychiatry, Fattouma Bourguiba Hospital, Monastir, Tunisia
| | - Amel Chaabane
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Zohra Chadli
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
| | - Karim Aouam
- Department of Clinical Pharmacology, Fattouma Bourguiba Hospital, Faculty of Medicine, University of Monastir, Monastir, Tunisia
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Russo M, Ignjatovic-Ristic D, Cohen D, Arenliu A, Bajraktarov S, Dzubur Kulenovic A, Injac Stevovic L, Maric N, Novotni A, Jovanovic N. Clozapine prescription rates in Southeast Europe: A cross-sectional study. Front Psychiatry 2023; 14:1123246. [PMID: 37113539 PMCID: PMC10126685 DOI: 10.3389/fpsyt.2023.1123246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 01/25/2023] [Indexed: 04/29/2023] Open
Abstract
Introduction International reports indicate that clozapine is under prescribed. Yet, this has not been explored in Southeast European (SEE) countries. This cross-sectional study investigates clozapine prescription rates in a sample of 401 outpatients with psychosis from Bosnia and Herzegovina, Kosovo by United Nations resolution, North Macedonia, Montenegro and Serbia. Methods Descriptive analysis was used to explore clozapine prescription rates; daily antipsychotic dosage was calculated and converted into olanzapine equivalents. Patients receiving clozapine were compared to those not receiving clozapine; next those that were on clozapine monotherapy were compared to those who were on clozapine polytherapy regime. Results It was showed that clozapine was prescribed to 37.7% of patients (with cross-country variation: from 25% in North Macedonia to 43.8% in Montenegro), with average dose of 130.7 mg/daily. The majority of patients on clozapine (70.5%) were prescribed at least one more antipsychotic (the most frequent combination was with haloperidol). Discussion Our findings suggested that clozapine prescription rate in SEE outpatients is higher than in Western Europe. The average dose is significantly below the optimal therapeutic dosage recommended by clinical guidelines, and clozapine polytherapy is common. This might indicate that clozapine is prescribed mainly for its sedative effect rather than antipsychotic. We hope that this finding will be taken up by relevant stakeholders to address this non-evidence-based practice.
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Affiliation(s)
- Manuela Russo
- Unit for Social and Community Psychiatry, Wolfson Institute of Population Health, Queen Mary University of London, London, United Kingdom
- Centre for Implementation Science, Health Services and Population Research Department, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, United Kingdom
- *Correspondence: Manuela Russo,
| | | | - Dan Cohen
- MHO North-Holland North, Heerhugowaard, Netherlands
| | - Aliriza Arenliu
- Department of Psychology, University of Pristina, Pristina, Kosovo by United Nations Resolution
| | | | | | | | - Nadja Maric
- Faculty of Medicine, Institute of Mental Health, University of Belgrade, Belgrade, Serbia
| | - Antoni Novotni
- University Clinic of Psychiatry, Skopje, North Macedonia
| | - Nikolina Jovanovic
- Unit for Social and Community Psychiatry, Wolfson Institute of Population Health, Queen Mary University of London, London, United Kingdom
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Adverse Drug Reactions in Relation to Clozapine Plasma Levels: A Systematic Review. Pharmaceuticals (Basel) 2022; 15:ph15070817. [PMID: 35890117 PMCID: PMC9317288 DOI: 10.3390/ph15070817] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/22/2022] [Accepted: 06/27/2022] [Indexed: 11/16/2022] Open
Abstract
Clozapine is the gold standard for treatment-resistant schizophrenia. Serious and even life-threatening adverse effects, mostly granulocytopenia, myocarditis, and constipation, are of great clinical concern and constitute a barrier to prescribing clozapine, thus depriving many eligible patients of a lifesaving treatment option. Interestingly, clozapine presents variable pharmacokinetics affected by numerous parameters, leading to significant inter- and intra-individual variation. Therefore, therapeutic drug monitoring of plasma clozapine levels confers a significant benefit in everyday clinical practice by increasing the confidence of the prescribing doctor to the drug and the adherence of the patient to the treatment, mainly by ensuring effective treatment and limited dose-related side effects. In the present systematic review, we aimed at identifying how a full range of adverse effects relates to plasma clozapine levels, using the Jadad grading system for assessing the quality of the available clinical evidence. Our findings indicate that EEG slowing, obsessive-compulsive symptoms, heart rate variability, hyperinsulinemia, metabolic syndrome, and constipation correlate to plasma clozapine levels, whereas QTc, myocarditis, sudden death, leucopenia, neutropenia, sialorrhea, are rather unrelated. Rapid dose escalation at the initiation of treatment might contribute to the emergence of myocarditis, or leucopenia. Strategies for managing adverse effects are different in these conditions and are discussed accordingly.
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Combining Therapeutic Drug Monitoring and Pharmacokinetic Modelling Deconvolutes Physiological and Environmental Sources of Variability in Clozapine Exposure. Pharmaceutics 2021; 14:pharmaceutics14010047. [PMID: 35056943 PMCID: PMC8779032 DOI: 10.3390/pharmaceutics14010047] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/13/2021] [Accepted: 12/22/2021] [Indexed: 11/17/2022] Open
Abstract
Background: Clozapine is a key antipsychotic drug for treatment-resistant schizophrenia but exhibits highly variable pharmacokinetics and a propensity for serious adverse effects. Currently, these challenges are addressed using therapeutic drug monitoring (TDM). This study primarily sought to (i) verify the importance of covariates identified in a prior clozapine population pharmacokinetic (popPK) model in the absence of environmental covariates using physiologically based pharmacokinetic (PBPK) modelling, and then to (ii) evaluate the performance of the popPK model as an adjunct or alternative to TDM-guided dosing in an active TDM population. Methods: A popPK model incorporating age, metabolic activity, sex, smoking status and weight was applied to predict clozapine trough concentrations (Cmin) in a PBPK-simulated population and an active TDM population comprising 142 patients dosed to steady state at Flinders Medical Centre in Adelaide, South Australia. Post hoc analyses were performed to deconvolute the impact of physiological and environmental covariates in the TDM population. Results: Analysis of PBPK simulations confirmed age, cytochrome P450 1A2 activity, sex and weight as physiological covariates associated with variability in clozapine Cmin (R2 = 0.7698; p = 0.0002). Prediction of clozapine Cmin using a popPK model based on these covariates accounted for <5% of inter-individual variability in the TDM population. Post hoc analyses confirmed that environmental covariates accounted for a greater proportion of the variability in clozapine Cmin in the TDM population. Conclusions: Variability in clozapine exposure was primarily driven by environmental covariates in an active TDM population. Pharmacokinetic modelling can be used as an adjunct to TDM to deconvolute sources of variability in clozapine exposure.
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Clinical and genetic influencing factors on clozapine pharmacokinetics in Tunisian schizophrenic patients. THE PHARMACOGENOMICS JOURNAL 2021; 21:551-558. [PMID: 33731885 DOI: 10.1038/s41397-021-00231-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 02/04/2021] [Accepted: 02/22/2021] [Indexed: 02/02/2023]
Abstract
Clozapine (Clz) is an atypical antipsychotic, which its pharmacokinetics can be influenced by several factors. The CYP1A2 and CYP2C19, major enzymes implicated in Clz metabolism, present an interethnic variation on their activity caused by single nucleotide polymorphisms (SNPs). The present study investigated the influence of genetic and nongenetic factors on Clz pharmacokinetics in a southern Mediterranean population. We included adult Tunisian schizophrenic patients having received Clz and undergone a therapeutic drug monitoring (TDM) of Clz by morning C0 monitoring. The genomic DNA was extracted using a salting-out procedure. CYP1A2*1F (rs762551;-163C>A), CYP1A2*1C (rs2069514;-3860 G>A) and CYP 2C19*2 (rs4244285; 681G>A) was analyzed using PCR-RFLP. Fifty-one patients were enrolled in the study. The mutant allele (CYP1A2*1F) was the most frequently detected (58.8%). For CYP1A2*1F, Clz dose-normalized (C0/D ratio) was as high as 1.28 ± 0.37 in CC versus 0.67 ± 0.32 ng mL-1 per mg day-1 in AA group (p < 0.001). The influence of genetic (CYP1A2*1F, CYP1A2*1C and CYP2C19*2) and nongenetic parameters (age, weight, gender, tobacco, coffee, and alcohol consumption) on the variation of the Clz C0/D ratio was investigated. Only the CYP1A2*1 F polymorphism correlates significantly with the Clz C0/D variation and could explain 24% of its variability. Our data support a critical role of the CYP1A2 -163C>A on the variation of Clz exposure in Tunisian schizophrenic patients. Considering its narrow therapeutic range, CYP1A2 genotyping combined with TDM of Clz may improve efficacy and safety of this drug. Further studies are needed to investigate this issue.
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Willcocks IR, Legge SE, Nalmpanti M, Mazzeo L, King A, Jansen J, Helthuis M, Owen MJ, O’Donovan MC, Walters JTR, Pardiñas AF. Clozapine Metabolism is Associated With Absolute Neutrophil Count in Individuals With Treatment-Resistant Schizophrenia. Front Pharmacol 2021; 12:658734. [PMID: 33959025 PMCID: PMC8094024 DOI: 10.3389/fphar.2021.658734] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/17/2021] [Indexed: 11/13/2022] Open
Abstract
Up to one-third of those with schizophrenia fail to respond to standard antipsychotics and are considered to have treatment-resistant schizophrenia, a condition for which clozapine is the only evidence-based medication. While up to 60% of treated individuals obtain therapeutic benefits from clozapine, it is currently underprescribed worldwide, partly because of concerns related to its broad adverse effect profile. In particular, the potential effects of clozapine on the immune system have gained relevance after a recent study showed that drug plasma concentrations were inversely correlated with neutrophil counts in individuals routinely undergoing treatment. Seeking to investigate this relationship in more detail, we extracted metabolic, immune, and genetic data from a UK cohort of long-term clozapine users linked to a clozapine monitoring service, CLOZUK2 (N = 208). Whilst a correlation analysis was compatible with the original results, a multiple linear regression accounting for dose and other confounding factors additionally allowed us to estimate the decrease in absolute neutrophil counts to approximately 141 cells/mm3 for every 0.1 mg/L increase in clozapine concentration. However, this association was attenuated after controlling for the metabolic ratio between clozapine and its main metabolite, norclozapine, which was itself negatively associated with neutrophil concentrations. Further analyses revealed that these relationships are likely moderated by genetic factors, as three pharmacogenomic SNPs previously associated to norclozapine plasma concentrations and the metabolic ratio (rs61750900, rs2011425 and rs1126545) were shown to be independently associated with a variation in neutrophil counts of about 400 cells/mm3 per effect allele. Such results are compatible with an effect of norclozapine, but not necessarily clozapine, on immune cell counts, and highlight the need for further investigations into the potential role of genetic determinants of clozapine pharmacokinetics in the occurrence of adverse effects during treatment.
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Affiliation(s)
- Isabella R. Willcocks
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Sophie E. Legge
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Mariana Nalmpanti
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Lucy Mazzeo
- Hafan y Coed Mental Health Unit, University Hospital of Llandough, Cardiff, United Kingdom
| | - Adrian King
- Magna Laboratories Ltd., Ross-on-Wye, United Kingdom
| | | | | | - Michael J. Owen
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Michael C. O’Donovan
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - James T. R. Walters
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Antonio F. Pardiñas
- MRC Centre for Neuropsychiatric Genetics and Genomics, Division of Psychological Medicine and Clinical Neurosciences, School of Medicine, Cardiff University, Cardiff, United Kingdom
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Whitlock K, Smith N, Poulsen RJ, Coffey BJ. Treatment-Resistant Depression in an Adolescent Treated with Clozapine: Weighing the Options in a Young Suicidal Patient. J Child Adolesc Psychopharmacol 2020; 30:342-344. [PMID: 32423223 DOI: 10.1089/cap.2020.29184.bjc] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Kevin Whitlock
- Department of Psychiatry and Behavioral Sciences and Jackson Behavioral Health Hospital, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Noah Smith
- Department of Psychiatry and Behavioral Sciences and Jackson Behavioral Health Hospital, University of Miami Miller School of Medicine, Miami, Florida, USA
| | | | - Barbara J Coffey
- Department of Psychiatry and Behavioral Sciences and Jackson Behavioral Health Hospital, University of Miami Miller School of Medicine, Miami, Florida, USA
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Albitar O, Harun SN, Zainal H, Ibrahim B, Sheikh Ghadzi SM. Population Pharmacokinetics of Clozapine: A Systematic Review. BIOMED RESEARCH INTERNATIONAL 2020; 2020:9872936. [PMID: 31998804 PMCID: PMC6970501 DOI: 10.1155/2020/9872936] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 12/10/2019] [Accepted: 12/19/2019] [Indexed: 12/19/2022]
Abstract
BACKGROUND AND OBJECTIVE Clozapine is a second-generation antipsychotic drug that is considered the most effective treatment for refractory schizophrenia. Several clozapine population pharmacokinetic models have been introduced in the last decades. Thus, a systematic review was performed (i) to compare published pharmacokinetics models and (ii) to summarize and explore identified covariates influencing the clozapine pharmacokinetics models. METHODS A search of publications for population pharmacokinetic analyses of clozapine either in healthy volunteers or patients from inception to April 2019 was conducted in PubMed and SCOPUS databases. Reviews, methodology articles, in vitro and animal studies, and noncompartmental analysis were excluded. RESULTS Twelve studies were included in this review. Clozapine pharmacokinetics was described as one-compartment with first-order absorption and elimination in most of the studies. Significant interindividual variations of clozapine pharmacokinetic parameters were found in most of the included studies. Age, sex, smoking status, and cytochrome P450 1A2 were found to be the most common identified covariates affecting these parameters. External validation was only performed in one study to determine the predictive performance of the models. CONCLUSIONS Large pharmacokinetic variability remains despite the inclusion of several covariates. This can be improved by including other potential factors such as genetic polymorphisms, metabolic factors, and significant drug-drug interactions in a well-designed population pharmacokinetic model in the future, taking into account the incorporation of larger sample size and more stringent sampling strategy. External validation should also be performed to the previously published models to compare their predictive performances.
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Affiliation(s)
- Orwa Albitar
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM, George Town, Penang, Malaysia
| | - Sabariah Noor Harun
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM, George Town, Penang, Malaysia
| | - Hadzliana Zainal
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM, George Town, Penang, Malaysia
| | - Baharudin Ibrahim
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, 11800 USM, George Town, Penang, Malaysia
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Qurashi I, Stephenson P, Nagaraj C, Chu S, Drake R, Couchman L, Flanagan R. Changes in smoking status, mental state and plasma clozapine concentration: retrospective cohort evaluation. BJPsych Bull 2019; 43:271-274. [PMID: 31391141 PMCID: PMC8058886 DOI: 10.1192/bjb.2019.50] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AIMS AND METHOD To investigate the percentage of patients who commenced smoking after transferring out of a non-smoking forensic psychiatric unit, the corresponding clozapine dose adjustments, the effects on plasma clozapine/norclozapine concentrations and observed changes in mental state. We reviewed the notes and plasma clozapine/norclozapine concentrations of 46 patients transferred to medium secure units between July 2008 and December 2013. RESULTS Thirty-five patients commenced smoking. Their median clozapine dose was increased by 50 mg/d. In the non-smokers, the median clozapine dose remained unchanged. Plasma clozapine/norclozapine concentrations were significantly reduced in smokers despite dosage adjustment. Eighteen patients experienced deterioration in mental state after transfer; almost all these patients were smokers. CLINICAL IMPLICATIONS Approximately three-quarters of patients who were non-smokers by virtue of being in a secure non-smoking environment commenced smoking after transfer. Monitoring of clozapine serum levels and assessment of mental state in the immediate period after a change in smoking status is indicated.
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Affiliation(s)
- Inti Qurashi
- High Secure Services, Ashworth High Secure Hospital, UK
| | | | | | - Simon Chu
- Department of Psychology, University of Central Lancashire, UK
| | - Richard Drake
- Division of Psychology and Mental Health, University of Manchester, UK
| | - Lewis Couchman
- Therapeutic Drug Monitoring, Analytical Services International, UK
| | - Robert Flanagan
- Toxicology, King's College Hospital NHS Foundation Trust, UK
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Dickens D, Rädisch S, Chiduza GN, Giannoudis A, Cross MJ, Malik H, Schaeffeler E, Sison-Young RL, Wilkinson EL, Goldring CE, Schwab M, Pirmohamed M, Nies AT. Cellular Uptake of the Atypical Antipsychotic Clozapine Is a Carrier-Mediated Process. Mol Pharm 2018; 15:3557-3572. [PMID: 29944835 DOI: 10.1021/acs.molpharmaceut.8b00547] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The weak base antipsychotic clozapine is the most effective medication for treating refractory schizophrenia. The brain-to-plasma concentration of unbound clozapine is greater than unity, indicating transporter-mediated uptake, which has been insufficiently studied. This is important, because it could have a significant impact on clozapine's efficacy, drug-drug interaction, and safety profile. A major limitation of clozapine's use is the risk of clozapine-induced agranulocytosis/granulocytopenia (CIAG), which is a rare but severe hematological adverse drug reaction. We first studied the uptake of clozapine into human brain endothelial cells (hCMEC/D3). Clozapine uptake into cells was consistent with a carrier-mediated process, which was time-dependent and saturable ( Vmax = 3299 pmol/million cells/min, Km = 35.9 μM). The chemical inhibitors lamotrigine, quetiapine, olanzapine, prazosin, verapamil, indatraline, and chlorpromazine reduced the uptake of clozapine by up to 95%. This could in part explain the in vivo interactions observed in rodents or humans for these compounds. An extensive set of studies utilizing transporter-overexpressing cell lines and siRNA-mediated transporter knockdown in hCMEC/D3 cells showed that clozapine was not a substrate of OCT1 (SLC22A1), OCT3 (SLC22A3), OCTN1 (SLC22A4), OCTN2 (SLC22A5), ENT1 (SLC29A1), ENT2 (SLC29A2), and ENT4/PMAT (SLC29A4). In a recent genome-wide analysis, the hepatic uptake transporters SLCO1B1 (OATP1B1) and SLCO1B3 (OATP1B3) were identified as additional candidate transporters. We therefore also investigated clozapine transport into OATP1B-transfected cells and found that clozapine was neither a substrate nor an inhibitor of OATP1B1 and OATP1B3. In summary, we have identified a carrier-mediated process for clozapine uptake into brain, which may be partly responsible for clozapine's high unbound accumulation in the brain and its drug-drug interaction profile. Cellular clozapine uptake is independent from currently known drug transporters, and thus, molecular identification of the clozapine transporter will help to understand clozapine's efficacy and safety profile.
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Affiliation(s)
- David Dickens
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Steffen Rädisch
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - George N Chiduza
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Athina Giannoudis
- Department of Molecular and Clinical Cancer Medicine , University of Liverpool , Liverpool L69 3BX , U.K
| | - Michael J Cross
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Hassan Malik
- Liverpool Hepatobiliary Unit , University Hospital Aintree , Liverpool L9 7AL , U.K
| | - Elke Schaeffeler
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology , 70376 Stuttgart , Germany.,University Tübingen , Tübingen , Germany
| | - Rowena L Sison-Young
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Emma L Wilkinson
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Christopher E Goldring
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Matthias Schwab
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology , 70376 Stuttgart , Germany.,Department of Clinical Pharmacology , University Hospital Tübingen , 72076 Tubingen , Germany.,Department of Pharmacy and Biochemistry , University Tübingen , 72076 Tübingen , Germany
| | - Munir Pirmohamed
- Department of Molecular and Clinical Pharmacology , University of Liverpool , Liverpool L69 3GL , U.K
| | - Anne T Nies
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology , 70376 Stuttgart , Germany.,University Tübingen , Tübingen , Germany
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12
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Genetic variants impacting metabolic outcomes among people on clozapine: a systematic review and meta-analysis. Psychopharmacology (Berl) 2017; 234:2989-3008. [PMID: 28879574 DOI: 10.1007/s00213-017-4728-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 08/23/2017] [Indexed: 12/11/2022]
Abstract
Clozapine is the gold standard medication for treatment refractory schizophrenia, but unfortunately, its use is also associated with many adverse metabolic side effects. There may be a strong genetic component to the development of these adverse effects. We undertook a systematic review to examine the evidence for genetic variation being associated with secondary metabolic outcomes in patients with schizophrenia on clozapine, under both longitudinal and cross-sectional study designs. We limited studies to those examining patients definitely taking clozapine, unlike prior reviews that have examined metabolic effects of patients taking a range of antipsychotic medications. We found associations with outcomes such as increases in BMI and metabolic syndrome for variants in genes such as LEP and HTR2C. Meta-analysis of rs381328 in HTR2C revealed that the presence of the T allele led to a 0.63 kg/m2 (95% CI - 1.06 to - 0.19; p = 0.005) decrease in BMI compared to the C allele. Study and population heterogeneity and lack of statistical power among reviewed articles mean that evidence is lacking to warrant prophylactic genotyping of patients commencing clozapine to predict those at increased risk of developing adverse metabolic effects. Further efforts to establish collaborative consortia, consensus around study design and replication studies in independent populations should be encouraged.
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Population Pharmacokinetics and Pharmacogenetics Analysis of Rilpivirine in HIV-1-Infected Individuals. Antimicrob Agents Chemother 2016; 61:AAC.00899-16. [PMID: 27799217 DOI: 10.1128/aac.00899-16] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 10/22/2016] [Indexed: 12/16/2022] Open
Abstract
Rilpivirine (RPV), the latest nonnucleoside reverse transcriptase inhibitor active against HIV-1, is prescribed in a standard dosage of 25 mg once a day in combination with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF). The aim of this observational study was to characterize the RPV pharmacokinetic profile, to quantify interpatient variability, and to identify potential factors that could influence drug exposure. RPV concentration data were collected from HIV-infected patients as part of routine therapeutic drug monitoring performed in our center (Laboratory of Clinical Pharmacology). A population pharmacokinetic analysis was performed with NONMEM by comparing various structural models. The influence of demographic and clinical covariates, as well as frequent genetic polymorphisms in 5 genes (CYP3A4*22, CYP3A5*3, CYP2C19*2, CYP2C19*17, UGT1A1*28, and UGT1A4*2), on RPV elimination was explored. A total of 325 plasma concentration measurements were obtained from 249 HIV-positive patients. Plasma concentrations ranged from 12 to 255 ng/ml. A one-compartment model with zero-order absorption best characterized RPV pharmacokinetics. The average RPV clearance (CL) was 11.7 liters/h, the average volume of distribution was 401 liters, and the mean absorption time was 4 h. The interinterindividual variability (IIV) for CL was estimated to be 33%. None of the available demographic or genetic covariates showed any influence on RPV pharmacokinetics, but 29% of the patients were predicted to present minimal concentrations below the recently identified target cutoff value of 50 ng/ml. The variability in RPV pharmacokinetics appears to be lower than that for most other antiretroviral drugs. However, under the standard regimen of 25 mg daily, a significant number of patients might be underdosed. It remains to be investigated whether the underexposure has an impact on the development of resistance while patients are on maintenance therapy.
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Fernandez-Egea E, Vértes PE, Flint SM, Turner L, Mustafa S, Hatton A, Smith KGC, Lyons PA, Bullmore ET. Peripheral Immune Cell Populations Associated with Cognitive Deficits and Negative Symptoms of Treatment-Resistant Schizophrenia. PLoS One 2016; 11:e0155631. [PMID: 27244229 PMCID: PMC4887013 DOI: 10.1371/journal.pone.0155631] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/01/2016] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Hypothetically, psychotic disorders could be caused or conditioned by immunological mechanisms. If so, one might expect there to be peripheral immune system phenotypes that are measurable in blood cells as biomarkers of psychotic states. METHODS We used multi-parameter flow cytometry of venous blood to quantify and determine the activation state of 73 immune cell subsets for 18 patients with chronic schizophrenia (17 treated with clozapine), and 18 healthy volunteers matched for age, sex, BMI and smoking. We used multivariate methods (partial least squares) to reduce dimensionality and define populations of differentially co-expressed cell counts in the cases compared to controls. RESULTS Schizophrenia cases had increased relative numbers of NK cells, naïve B cells, CXCR5+ memory T cells and classical monocytes; and decreased numbers of dendritic cells (DC), HLA-DR+ regulatory T-cells (Tregs), and CD4+ memory T cells. Likewise, within the patient group, more severe negative and cognitive symptoms were associated with decreased relative numbers of dendritic cells, HLA-DR+ Tregs, and CD4+ memory T cells. Motivated by the importance of central nervous system dopamine signalling for psychosis, we measured dopamine receptor gene expression in separated CD4+ cells. Expression of the dopamine D3 (DRD3) receptor was significantly increased in clozapine-treated schizophrenia and covaried significantly with differentiated T cell classes in the CD4+ lineage. CONCLUSIONS Peripheral immune cell populations and dopaminergic signalling are disrupted in clozapine-treated schizophrenia. Immuno-phenotypes may provide peripherally accessible and mechanistically specific biomarkers of residual cognitive and negative symptoms in this treatment-resistant subgroup of patients.
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Affiliation(s)
- Emilio Fernandez-Egea
- NIHR Cambridge Biomedical Research Centre, Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge, Cambridge, United Kingdom
- University of Cambridge, Behavioural & Clinical Neuroscience Institute, Department of Psychiatry, Cambridge, United Kingdom
- Centro de Investigación Biomedica en Red de Salud Mental (CIBERSAM), G04, Barcelona, Spain
- Cambridgeshire & Peterborough NHS Foundation Trust, Cambridge, United Kingdom
| | - Petra E. Vértes
- University of Cambridge, Behavioural & Clinical Neuroscience Institute, Department of Psychiatry, Cambridge, United Kingdom
| | - Shaun M. Flint
- Department of Medicine and Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine, Cambridge, United Kingdom
| | - Lorinda Turner
- NIHR Cambridge Biomedical Research Centre, Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge, Cambridge, United Kingdom
- Department of Medicine and Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine, Cambridge, United Kingdom
| | - Syed Mustafa
- University of Cambridge, Behavioural & Clinical Neuroscience Institute, Department of Psychiatry, Cambridge, United Kingdom
| | - Alex Hatton
- Department of Medicine and Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine, Cambridge, United Kingdom
| | - Kenneth G. C. Smith
- NIHR Cambridge Biomedical Research Centre, Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge, Cambridge, United Kingdom
- Department of Medicine and Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine, Cambridge, United Kingdom
| | - Paul A. Lyons
- Department of Medicine and Cambridge Institute for Medical Research, University of Cambridge, School of Clinical Medicine, Cambridge, United Kingdom
| | - Edward T. Bullmore
- NIHR Cambridge Biomedical Research Centre, Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge, Cambridge, United Kingdom
- University of Cambridge, Behavioural & Clinical Neuroscience Institute, Department of Psychiatry, Cambridge, United Kingdom
- Cambridgeshire & Peterborough NHS Foundation Trust, Cambridge, United Kingdom
- GlaxoSmithKline, ImmunoPsychiatry, Alternative Discovery & Development, Pharmaceutical R&D, Cambridge, United Kingdom
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