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Abstract
OBJECTIVE Clozapine is generally recommended to be prescribed in a divided dosing regimen based on its relatively short plasma half-life. However, there has been little evidence to support the superiority of divided dosing of clozapine over once-daily dosing. To our knowledge, there have been no studies examining differences in actual plasma concentrations or adverse effects between the 2 dosing strategies of clozapine. We aimed to compare actual plasma concentrations of clozapine between once-daily and divided dosing regimens, and to examine the relationships of these regimens with psychiatric symptoms and adverse effects of clozapine. METHODS We analyzed data from 108 participants of a previous study conducted in 2 hospitals in Japan. A population pharmacokinetic model was used to estimate the peak and trough plasma concentrations of clozapine based on actual plasma concentrations. We evaluated psychiatric symptoms with the Brief Evaluation of Psychosis Symptom Domains and adverse effects of clozapine with the Glasgow Antipsychotic Side-effects Scale for Clozapine. RESULTS The estimated peak and trough plasma concentrations of clozapine did not differ significantly between once-daily and divided dosing regimens. There were no significant differences in psychiatric symptoms except for depression/anxiety or subjective adverse effects of clozapine between the 2 dosing strategies. CONCLUSIONS Our findings tentatively support the feasibility and clinical utility of once-daily dosing of clozapine in clinical practice. Further studies are needed to replicate these findings and determine causality between dosing strategies and clinical outcomes.
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Nomura N, Kitagawa K, So R, Misawa F, Kodama M, Takeuchi H, Bies R, Straubinger T, Banker C, Mizuno Y, Mimura M, Uchida H. Comprehensive assessment of exposure to clozapine in association with side effects among patients with treatment-resistant schizophrenia: a population pharmacokinetic study. Ther Adv Psychopharmacol 2021; 11:20451253211016189. [PMID: 34046160 PMCID: PMC8138292 DOI: 10.1177/20451253211016189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/20/2021] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND There have been scarce data on the distribution of clozapine concentrations in comparison with the recommended range (350-600 ng/ml) or their relationship with side effects among patients with treatment-resistant schizophrenia. Furthermore, no studies have assessed the association between side effects and overall exposure to the drug by calculating the 24-h area-under-curve (AUC). METHODS In- and outpatients with schizophrenia or schizoaffective disorder (ICD-10) who were receiving a stable dose of clozapine for ⩾2 weeks were included. Side effects were assessed using the Glasgow antipsychotic side-effects scale for clozapine (GASS-C). Using two collected plasma samples, plasma clozapine and norclozapine concentrations at peak and trough and their 24-h AUC were estimated using population pharmacokinetic models. RESULTS A total of 108 patients completed the study (mean ± SD age, 43.0 ± 10.1 years; clozapine dose, 357.5 ± 136.9 mg/day); 33 patients (30.6%) showed estimated trough concentrations of clozapine within the recommended range (350-600 ng/ml) whereas the concentrations were higher and lower than this range among 37 (43.5%) and 28 (25.9%) patients (%), respectively. There were no significant correlations between estimated peak or trough concentrations or 24-h AUC of both clozapine or norclozapine, and GASS-C total or individual scores. No significant differences were found between GASS-C total or individual item scores between the patients with estimated trough concentrations of clozapine of >600 ng/ml and the other subjects. CONCLUSION The results suggest that clozapine or norclozapine concentrations are not linked directly to the extent of side effects experienced in clozapine-treated patients with treatment-resistant schizophrenia while the cross-sectional study design limits the interpretation of any causal relationships. These findings indicate that side effects associated with clozapine may occur at any dose or concentration.
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Affiliation(s)
- Nobuyuki Nomura
- Department of Neuropsychiatry, Yamanashi Prefectural Kita Hospital, Yamanashi, Japan
| | - Kohei Kitagawa
- Department of Neuropsychiatry, Okayama Psychiatric Medical Center, 3-16, Shikatahonmachi, Kita-ku, Okayama-shi, Okayama, 700-0915, Japan
| | - Ryuhei So
- Department of Neuropsychiatry, Okayama Psychiatric Medical Center, 3-16, Shikatahonmachi, Kita-ku, Okayama-shi, Okayama, 700-0915, Japan
| | - Fuminari Misawa
- Department of Neuropsychiatry, Yamanashi Prefectural Kita Hospital, Yamanashi, Japan
| | - Masafumi Kodama
- Department of Neuropsychiatry, Okayama Psychiatric Medical Center, Okayama, Japan
| | - Hiroyoshi Takeuchi
- Department of Neuropsychiatry, Yamanashi Prefectural Kita Hospital, Yamanashi, Japan
| | - Robert Bies
- Department of Pharmaceutical Sciences, University at Buffalo, New York, USA
| | - Thomas Straubinger
- Department of Pharmaceutical Sciences, University at Buffalo, New York, USA
| | - Christopher Banker
- Department of Pharmaceutical Sciences, University at Buffalo, New York, USA
| | - Yuya Mizuno
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Masaru Mimura
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Hiroyuki Uchida
- Department of Neuropsychiatry, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
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