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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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Berneri M, Jha U, O'Halloran S, Salman S, Wickramasinghe S, Kendrick K, Nguyen J, Joyce DA. Validation of Population Pharmacokinetic Models for Clozapine Dosage Prediction. Ther Drug Monit 2024; 46:217-226. [PMID: 38446630 DOI: 10.1097/ftd.0000000000001184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/03/2023] [Indexed: 03/08/2024]
Abstract
BACKGROUND Clozapine is unique in its capacity to ameliorate severe schizophrenia but at high risk of toxicity. A relationship between blood concentration and clinical response and evidence for concentration-response relationships to some adverse effects justify therapeutic drug monitoring of clozapine. However, the relationship between drug dose and blood concentration is quite variable. This variability is, in part, due to inductive and inhibitory interactions varying the activity of cytochrome P450 1A2 (CYP1A2), the principal pathway for clozapine elimination. Several population pharmacokinetic models have been presented to facilitate dose selection and to identify poor adherence in individual patients. These models have faced little testing for validity in independent populations or even for persisting validity in the source population. METHODS Therefore, we collected a large population of clozapine-treated patients (127 patients, 1048 timed plasma concentrations) in whom dosing and covariate information could be obtained with high certainty. A population pharmacokinetic model was constructed with data collected in the first 6 weeks from study enrolment (448 plasma concentrations), to estimate covariate influences and to allow alignment with previously published models. The model was tested for its performance in predicting the concentrations observed at later time intervals up to 5 years. The predictive performances of 6 published clozapine population models were then assessed in the entire population. RESULTS The population pharmacokinetic model based on the first 6 weeks identified significant influences of sex, smoking, and cotreatment with fluvoxamine on clozapine clearance. The model built from the first 6 weeks had acceptable predictive performance in the same patient population up to the first 26 weeks using individual parameters, with a median predictive error (PE) of -0.1% to -15.9% and median absolute PE of 22.9%-27.1%. Predictive performance fell progressively with time after 26 weeks. Bayesian addition of plasma concentration observations within each prediction period improved individual predictions. Three additional observations extended acceptable predictive performance into the second 6 months of therapy. When the published models were tested with the entire data set, median PE ranged from -8% to +35% with a median absolute PE of >39% in all models. Thus, none of the tested models was successful in external validation. Bayesian addition of single patient observations improved individual predictions from all models but still without achieving acceptable performances. CONCLUSIONS We conclude that the relationship between covariates and blood clozapine concentrations differs between populations and that relationships are not stable over time within a population. Current population models for clozapine are not capturing influential covariates.
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Affiliation(s)
- Massimo Berneri
- Schools of Medicine & Biomedical Sciences, University of Western Australia, Crawley, Western Australia, Australia
| | - Uma Jha
- Schools of Medicine & Biomedical Sciences, University of Western Australia, Crawley, Western Australia, Australia
| | - Seán O'Halloran
- Clinical Pharmacology & Toxicology, PathWest Laboratory Medicine, Nedlands, Western Australia, Australia
| | - Sam Salman
- Clinical Pharmacology & Toxicology, PathWest Laboratory Medicine, Nedlands, Western Australia, Australia
- Medical School, University of Western Australia, Crawley, Western Australia, Australia
| | | | - Kevin Kendrick
- Fremantle Hospital Mental Health Service, Fremantle, Western Australia, Australia
| | - Jessica Nguyen
- Department of Pharmacy, Graylands Hospital, Mount Claremont, Western Australia, Australia ; and
| | - David A Joyce
- Schools of Medicine & Biomedical Sciences, University of Western Australia, Crawley, Western Australia, Australia
- Clinical Pharmacology & Toxicology, PathWest Laboratory Medicine, Nedlands, Western Australia, Australia
- Department of Clinical Pharmacology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
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Jiménez-Fernández S, Gurpegui M, Correll CU, de Leon J, Schoretsanitis G. A Systematic Review of Clozapine Concentration-Dose Ratio from Therapeutic Drug Monitoring Studies in Children and Adolescents Treated with Clozapine for Mental Disorders. Ther Drug Monit 2024; 46:170-180. [PMID: 38018845 PMCID: PMC10930379 DOI: 10.1097/ftd.0000000000001154] [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: 07/31/2023] [Accepted: 09/14/2023] [Indexed: 11/30/2023]
Abstract
BACKGROUND Therapeutic drug monitoring of clozapine in children and adolescents has received insufficient attention. Calculation of concentration-to-dose (C/D) ratios from trough steady-state concentrations estimate drug clearance. METHODS A systematic electronic literature search was conducted in 3 article databases from inception until January 10, 2023, and articles reporting clozapine concentrations in children and adolescents were retrieved. The pharmacokinetic quality of the studies was assessed, and clozapine C/D ratios were calculated using the sample mean clozapine dose and concentration. RESULTS Of the 37 articles of potential interest, only 7 reported clozapine trough and steady-state concentrations. After excluding case reports and a study confounded by fluvoxamine, 4 studies on psychosis from Europe and the United States were included. The clozapine C/D ratios were similar to published adult values and ranged from 0.82 to 1.24 with a weighted mean of 1.08 ng/mL per mg/d. The weighted means were 334 mg/d for the dose and 380 ng/mL for the concentration. The stratified analysis of the weighted mean clozapine C/D ratios from 2 studies showed lower values in 52 male (1.05 ng/mL per mg/d) than in 46 female (1.46 ng/mL per mg/d) children and adolescents, with values similar to those reported for European adult nonsmokers. Two female adolescents had high clozapine C/D ratios (2.54 ng/mL per mg/d), an Asian American patient with borderline obesity and a patient with intellectual disability with low dosage (mean = 102 mg/d) and concentration (mean = 55 ng/mL). CONCLUSIONS Reports on clozapine therapeutic drug monitoring in children and adolescents are limited in number and quality. Future studies should focus on basic pharmacokinetic issues, such as stratification by sex, smoking, and relevant comedications with inductive or inhibitory properties.
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Affiliation(s)
- Sara Jiménez-Fernández
- Child and Adolescent Mental Health Unit, Virgen de Las Nieves University Hospital, Granada, Spain
- CTS-549 Research Group (Psychiatry and Neurosciences), Junta de Andalucía, Spain
| | - Manuel Gurpegui
- CTS-549 Research Group (Psychiatry and Neurosciences), Junta de Andalucía, Spain
- Granada Center for Psychiatric Studies, Granada, Spain
| | - Christoph U. Correll
- Department of Child and Adolescent Psychiatry, Charité Universitätsmedizin, Berlin, Germany
- The Zucker Hillside Hospital, Psychiatry Research, Northwell Health, Glen Oaks, New York
- Department of Psychiatry, Zucker School of Medicine at Northwell/Hofstra, Hempstead, New York
| | - Jose de Leon
- Mental Health Research Center, Eastern State Hospital, Lexington, Kentucky
- Biomedical Research Centre in Mental Health Net (CIBERSAM), Santiago Apóstol Hospital, University of the Basque Country, Vitoria, Spain; and
| | - Georgios Schoretsanitis
- The Zucker Hillside Hospital, Psychiatry Research, Northwell Health, Glen Oaks, New York
- Department of Psychiatry, Zucker School of Medicine at Northwell/Hofstra, Hempstead, New York
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zürich, Zürich, Switzerland
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Geers LM, Cohen D, Wehkamp LM, van Wattum HJ, Kosterink JGW, Loonen AJM, Touw DJ. Population pharmacokinetic model and limited sampling strategy for clozapine using plasma and dried blood spot samples. Ther Adv Psychopharmacol 2022; 12:20451253211065857. [PMID: 35518123 PMCID: PMC9066631 DOI: 10.1177/20451253211065857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 11/23/2021] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND To improve efficacy, therapeutic drug monitoring is often used in clozapine therapy. Trough level monitoring is regular, but trough levels provide limited information about the pharmacokinetics of clozapine and exposure in time. The area under the concentration time curve (AUC) is generally valued as better marker of drug exposure in time but calculating AUC needs multiple sampling. An alternative approach is a limited sampling scheme in combination with a population pharmacokinetic model meant for Bayesian forecasting. Furthermore, multiple venepunctions can be a burden for the patient, whereas collecting samples by means of dried blood spot (DBS) sampling can facilitate AUC-monitoring, making it more patient friendly. OBJECTIVE Development of a population pharmacokinetic model and limited sampling strategy for estimating AUC0-12h (a twice-daily dosage regimen) and AUC0-24h (a once-daily dosage regimen) of clozapine, using a combination of results from venepunctions and DBS sampling. METHOD From 15 schizophrenia patients, plasma and DBS samples were obtained before administration and 2, 4, 6, and 8 h after clozapine intake. MwPharm® pharmacokinetic software was used to parameterize a population pharmacokinetic model and calculate limited sampling schemes. RESULTS A three-point sampling strategy with samples at 2, 6, and 8 h after clozapine intake gave the best estimation of the clozapine AUC0-12h and at 4, 10, and 11 h for the AUC0-24h. For clinical practice, however, a two-point sampling strategy with sampling points at 2 and 6 h was sufficient to estimate AUC0-12h and at 4 and 11 h for AUC0-24h. CONCLUSION A pharmacokinetic model with a two-time point limited sampling strategy meant for Bayesian forecasting using DBS sampling gives a better prediction of the clozapine exposure in time, expressed as AUC, compared to trough level monitoring. This limited sampling strategy might therefore provide a more accurate prediction of effectiveness and occurrence of side effects compared to trough level monitoring. The use of DBS samples also makes the collection of clozapine samples easier and wider applicable.
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Affiliation(s)
- Lisanne M Geers
- Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Dan Cohen
- FACT-Team Heerhugowaard, Department of Community Psychiatry, Mental Health Organization North-Holland North, Heerhugowaard, The Netherlands
| | - Laura M Wehkamp
- Department of Clinical Pharmacy, Medisch Spectrum Twente, Enschede, The Netherlands
| | | | - Jos G W Kosterink
- Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Anton J M Loonen
- Pharmacotherapy, -Epidemiology & -Economics, Groningen Research Institute of Pharmacy, University of Groningen, Groningen, The Netherlands
| | - Daan J Touw
- Department of Clinical Pharmacy and Pharmacology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
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A systematic review and meta-analysis of the association between clozapine and norclozapine serum levels and peripheral adverse drug reactions. Psychopharmacology (Berl) 2021; 238:615-637. [PMID: 33410989 DOI: 10.1007/s00213-020-05746-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/01/2020] [Indexed: 12/13/2022]
Abstract
RATIONALE Clozapine is the most effective antipsychotic for treatment-refractory schizophrenia for reducing positive psychotic symptoms. It is associated with a reduction in hospitalisation and overall mortality. In spite of this, clozapine remains underutilised due to its complex adverse drug reaction (ADR) profile. OBJECTIVE This systematic review aims to investigate the association of clozapine and norclozapine serum levels, and peripheral ADRs. METHODS Studies were searched from four electronic databases (PubMed, EMBASE, PsycINFO and CINAHL) from inception to 12 June 2020. Studies were included if they had adult patients, provided data on steady-state trough clozapine or norclozapine levels and reported on clozapine-associated ADRs. Pregnant women, case reports and series were excluded. RESULTS A statistically significant correlation was found for clozapine serum levels and triglycerides (n = 70; r = 0.303, 95% CI 0.0119-0.546, p = 0.042), heart rate (n = 137; r = 0.269, 95% CI 0.0918-0.486, p = 0.035), and overall combined ADRs (n = 160; r = 0.264, 95% CI 0.110-0.405, p = 0.001), but not for absolute neutrophil count (n = 223; r = - 0.164, 95% CI - 0.529-0.253, p = 0.444) or total white cell count (n = 18; r = 0.0176, 95% CI - 0.203-0.237, p = 0.878). Interestingly, norclozapine serum levels were found to be statistically correlated to triglycerides (n = 120; r = 0.211, 95% CI 0.0305-0.378, p = 0.022), total cholesterol (n = 120; r = 0.272, 95% CI 0.0948-0.432, p = 0.003) and weight gain (n = 118; r = 0.208, 95% CI 0.0261-0.377, p = 0.025). CONCLUSIONS Heart rate, triglycerides and combined ADRs are significantly correlated with clozapine levels, and triglycerides, total cholesterol and weight gain with norclozapine levels. Future prospective, randomised controlled studies are needed to identify the cause-effect relationship between clozapine levels and peripheral ADRs.
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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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Given the Data of Hommers and Colleagues, Valproic Acid Is Not an Unequivocal Inducer of Clozapine Metabolism. J Clin Psychopharmacol 2019; 39:419-420. [PMID: 31188239 DOI: 10.1097/jcp.0000000000001072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Population pharmacokinetics of clozapine and its primary metabolite norclozapine in Chinese patients with schizophrenia. Acta Pharmacol Sin 2012; 33:1409-16. [PMID: 22820910 DOI: 10.1038/aps.2012.71] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
AIM To develop a combined population pharmacokinetic model (PPK) to assess the magnitude and variability of exposure to both clozapine and its primary metabolite norclozapine in Chinese patients with refractory schizophrenia via sparse sampling with a focus on the effects of covariates on the pharmacokinetic parameters. METHODS Relevant patient concentration data (eg, demographic data, medication history, dosage regimen, time of last dose, sampling time, concentrations of clozapine and norclozapine, etc) were collected using a standardized data collection form. The demographic characteristics of the patients, including sex, age, weight, body surface area, smoking status, and information on concomitant medications as well as biochemical and hematological test results were recorded. Persons who had smoked 5 or more cigarettes per day within the last week were defined as smokers. The concentrations of clozapine and norclozapine were measured using a HPLC system equipped with a UV detector. PPK analysis was performed using NONMEM. Age, weight, sex, and smoking status were evaluated as main covariates. The model was internally validated using normalized prediction distribution errors. RESULTS A total of 809 clozapine concentration data sets and 808 norclozapine concentration data sets from 162 inpatients (74 males, 88 females) at multiple mental health sites in China were included. The one-compartment pharmacokinetic model with mixture error could best describe the concentration-time profiles of clozapine and norclozapine. The population-predicted clearance of clozapine and norclozapine in female nonsmokers were 21.9 and 32.7 L/h, respectively. The population-predicted volumes of distribution for clozapine and norclozapine were 526 and 624 L, respectively. Smoking was significantly associated with increases in the clearance (clozapine by 45%; norclozapine by 54.3%). The clearance was significantly greater in males than in females (clozapine by 20.8%; norclozapine by 24.2%). The clearance of clozapine and norclozapine did not differ significantly between Chinese patients and American patients. CONCLUSION Smoking and male were significantly associated with a lower exposure to clozapine and norclozapine due to higher clearance. This model can be used in individualized drug dosing and therapeutic drug monitoring.
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Maehara S, Hikichi H, Ohta H. Behavioral effects of N-desmethylclozapine on locomotor activity and sensorimotor gating function in mice—Possible involvement of muscarinic receptors. Brain Res 2011; 1418:111-9. [DOI: 10.1016/j.brainres.2011.08.056] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 08/20/2011] [Accepted: 08/22/2011] [Indexed: 10/17/2022]
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Maehara S, Satow A, Hikichi H, Ohta H. Antipsychotic effects of N-desmethylclozapine on sensorimotor gating function in rats — Possible involvement of activation of M1 muscarinic receptors. Eur J Pharmacol 2011; 667:242-9. [DOI: 10.1016/j.ejphar.2011.05.063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 05/09/2011] [Accepted: 05/22/2011] [Indexed: 12/01/2022]
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Maehara S, Okuda S, Ohta H. Ameliorative effect of N-desmethylclozapine in animal models of social deficits and cognitive functions. Brain Res Bull 2011; 86:146-51. [PMID: 21855612 DOI: 10.1016/j.brainresbull.2011.08.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 07/30/2011] [Accepted: 08/02/2011] [Indexed: 10/17/2022]
Abstract
One of the major circulating metabolites of clozapine, N-desmethylclozapine (NDMC), has been demonstrated to exhibit partial agonistic activity at M(1) muscarinic receptors. Some of the unique therapeutic effects of clozapine might involve the pharmacological effects of this metabolite. The purpose of the present study was therefore to examine whether NDMC improved behavioral abnormalities in animal models of social deficits and cognitive deficits of schizophrenia. NDMC (3mg/kg) and clozapine (1-3mg/kg) each improved the reduction of social interaction caused by a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, 5R,10S-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) (0.1mg/kg), without affecting locomotor activity in rats. NDMC (3-10mg/kg) and clozapine (1-3mg/kg) each also resulted in better discrimination of a novel from a familiar object 24h after a training trial in a rat object recognition test. These findings suggest that NDMC can improve behavior in animal models of social deficits and cognitive deficits of schizophrenia as well as clozapine.
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Chetty M, d'Esposito F, Zhang WV, Glen J, Dore G, Stankovic Z, Edwards RJ, Ramzan I, Murray M. In vitro and in vivo evaluation of the inhibition potential of risperidone toward clozapine biotransformation. Br J Clin Pharmacol 2010; 68:574-9. [PMID: 19843060 DOI: 10.1111/j.1365-2125.2009.03476.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
AIMS To study the impact of risperidone (RISP) on clozapine (CLZ) biotransformation in vitro in microsomal fractions containing varying expression of CYP oxidases and in vivo in patients. METHODS Human liver microsomes (n= 11) were assessed for expression of CYPs 1A2, 2D6 and 3A4, because these enzymes mediate RISP and CLZ oxidation. Inhibition of CLZ oxidation by RISP was assessed. Plasma CLZ elimination was estimated in patients with schizophrenia who received either CLZ alone or the CLZ-RISP combination (n= 10 per group). RESULTS (i) The CYP3A4 and CYP1A2 inhibitors ketoconazole and fluvoxamine inhibited CLZ oxidation to varying extents in individual microsomal fractions. (ii) RISP did not inhibit CLZ oxidation, regardless of variations in CYP expression. (iii) RISP co-administration did not impair CLZ clearance. CONCLUSIONS No evidence was found for CYP-mediated inhibitory or pharmacokinetic interactions between RISP and CLZ. Occasional literature reports of such interactions may involve other pathways that participate in CLZ disposition.
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Clozapine exposure and the impact of smoking and gender: a population pharmacokinetic study. Ther Drug Monit 2009; 31:360-6. [PMID: 19349931 DOI: 10.1097/ftd.0b013e31819c7037] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The primary objective of this study was to evaluate the magnitude and variability of concentration exposure to clozapine and norclozapine in a real-world clinical setting, with a focus on smoking status, using population pharmacokinetic methodologies. A retrospective review of plasma clozapine and norclozapine concentrations taken from inpatients at the Centre for Addiction and Mental Health, Toronto, from 2001 to 2007 was conducted. A nonlinear mixed-effects model was developed using NONMEM, including age, gender, weight, smoking status, and dosage formulation as covariates. Pharmacokinetic parameters and interindividual and residual variabilities were estimated with 1- and 2-compartment models. A total of 519 plasma clozapine concentrations from 197 patients (138 males; mean +/- SD age, 38 +/- 13 years; schizophrenia spectrum disorder 98.2%) were included for the analysis. A 1-compartment model with first-order absorption and elimination best described the data. Apparent volume of distribution was fixed to a previously reported value in the literature of 7 L/kg.The population-predicted oral clearance of clozapine and norclozapine was 18.0 and 39.0 L/h, respectively; both the predicted clearance values vary nearly 6-fold (range, 9.18-59.06 and 16.29-97.84 L/h, respectively). For clozapine, smokers and males showed increased oral clearance by 6.0 and 4.5 L/h, respectively. For norclozapine, smokers and male gender were associated with an increased oral clearance of 11.3 and 7.6 L/h, respectively. The formulation of clozapine administered had an impact on the absorption rate with a Ka of 0.14/h for tablet and 10.3/h for the suspension form.The data suggest that smoking and male gender are associated with lower exposure to clozapine and norclozapine due to the higher oral clearance. These findings may account for some of the variability in clozapine exposure and have important implications for individualized drug dosing and therapeutic drug monitoring.
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Doude van Troostwijk LJAE, Koopmans RP, Vermeulen HDB, Guchelaar HJ. CYP1A2 activity is an important determinant of clozapine dosage in schizophrenic patients. Eur J Pharm Sci 2004; 20:451-7. [PMID: 14659489 DOI: 10.1016/j.ejps.2003.09.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Clozapine is an effective atypical antipsychotic drug applied in the treatment of resistant schizophrenia. The drug is mainly metabolized by cytochrome P-450 (CYP) enzymes especially the isozyme CYP1A2. Remarkably, the effective dosage varies widely among patients, making it necessary to individualize drug therapy with clozapine. The explanation for dosage variation may be differences in drug metabolism, and more specifically of CYP1A2 activity. This study is aimed at determining to what extent variability in clozapine dose can be explained by pharmacokinetic (PK) factors and more specifically by CYP1A2 activity in effectively treated psychiatric patients. In 22 evaluable patients with a schizophrenic disorder chronically using clozapine, the CYP1A2 activity and the clozapine clearance were estimated. For calculation of the pharmacokinetic parameters of clozapine, population PK software based upon Bayesian analysis was used. Caffeine clearance was estimated with the paraxanthine/caffeine ratio and served as estimate of CYP1A2 activity.A significant linear relationship was found between the clozapine dose and clozapine clearance (R: 0.71; P<0.05), whereas no relationship was found between clozapine dosage and clozapine serum trough concentration. Moreover, individual caffeine and clozapine clearances were found to be significantly related (R: 0.62; P<0.05) as were clozapine dose per kg body weight and P/C mol ratio (R: 0.44; P<0.05). We conclude that CYP1A2 activity is an important determinant of the variability of effective clozapine doses in psychiatric patients.
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Affiliation(s)
- Lous J A E Doude van Troostwijk
- Department of Clinical Pharmacy, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, NL 1105 AZ Amsterdam, The Netherlands
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Sur C, Mallorga PJ, Wittmann M, Jacobson MA, Pascarella D, Williams JB, Brandish PE, Pettibone DJ, Scolnick EM, Conn PJ. N-desmethylclozapine, an allosteric agonist at muscarinic 1 receptor, potentiates N-methyl-D-aspartate receptor activity. Proc Natl Acad Sci U S A 2003; 100:13674-9. [PMID: 14595031 PMCID: PMC263872 DOI: 10.1073/pnas.1835612100] [Citation(s) in RCA: 223] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The molecular and neuronal substrates conferring on clozapine its unique and superior efficacy in the treatment of schizophrenia remain elusive. The interaction of clozapine with many G protein-coupled receptors is well documented but less is known about its biologically active metabolite, N-desmethylclozapine. Recent clinical and preclinical evidences of the antipsychotic activity of the muscarinic agonist xanomeline prompted us to investigate the effects of N-desmethylclozapine on cloned human M1-M5 muscarinic receptors. N-desmethylclozapine preferentially bound to M1 muscarinic receptors with an IC50 of 55 nM and was a more potent partial agonist (EC50, 115 nM and 50% of acetylcholine response) at this receptor than clozapine. Furthermore, pharmacological and site-directed mutagenesis studies suggested that N-desmethylclozapine preferentially activated M1 receptors by interacting with a site that does not fully overlap with the acetylcholine orthosteric site. As hypofunction of N-methyl-d-aspartate (NMDA) receptor-driven neuronal ensembles has been implicated in psychotic disorders, the neuronal activity of N-desmethylclozapine was electrophysiologically investigated in hippocampal rat brain slices. N-desmethylclozapine was shown to dose-dependently potentiate NMDA receptor currents in CA1 pyramidal cells by 53% at 100 nM, an effect largely mediated by activation of muscarinic receptors. Altogether, our observations provide direct evidence that the brain penetrant metabolite N-desmethylclozapine is a potent, allosteric agonist at human M1 receptors and is able to potentiate hippocampal NMDA receptor currents through M1 receptor activation. These observations raise the possibility that N-desmethylclozapine contributes to clozapine's clinical activity in schizophrenics through modulation of both muscarinic and glutamatergic neurotransmission.
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Affiliation(s)
- Cyrille Sur
- Department of Neuroscience, Merck & Co. Inc., West Point, PA 19486, USA.
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Guitton C, Kinowski JM, Abbar M, Chabrand P, Bressolle F. Clozapine and metabolite concentrations during treatment of patients with chronic schizophrenia. J Clin Pharmacol 1999; 39:721-8. [PMID: 10392327 DOI: 10.1177/00912709922008245] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Results presented in this article are focused on the variability in pharmacokinetics. The purpose of this study was (1) to investigate intra- and interindividual variabilities of pharmacokinetic parameters of clozapine and its two main metabolites in plasma after multiple oral administration in 8 chronic schizophrenic patients (Study 1) and (2) to gain more information regarding plasma concentrations of these drugs after multiple doses in a group of 25 treatment-responsive patients (Study 2). Patients were treated with clozapine in fixed daily doses (given every 8-12 hours) between 200 and 900 mg. Plasma drug concentrations were determined by high-performance liquid chromatography. The mean volume of distribution and the total plasma clearance of clozapine, uncorrected for bioavailability, were 7 L/kg and 40.5 L/h, respectively. The terminal elimination half-lives averaged 10.5 hours for clozapine, 19.2 hours for norclozapine, and 8.6 hours for the N-oxide metabolite. Significant relationships were observed between clozapine and norclozapine (or clozapine N-oxide) plasma concentrations. Large inter- and intrapatient variations in pharmacokinetics were observed. Clozapine was generally well tolerated by the patients, with sedation, hypersialorrhea, and tiredness as the most common side effects encountered.
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Affiliation(s)
- C Guitton
- Laboratoire de Pharmacocinétique, Hôpital Carémeau, Nîmes, France
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