Influence of dose, gender, and cigarette smoking on clozapine plasma concentrations

Michaela Mayerova,1–3 Libor Ustohal,1–3 Jiri Jarkovsky,4 Jan Pivnicka,1,5 Tomas Kasparek,1,2 Eva Ceskova1,3 1Faculty of Medicine, Masaryk University, Brno, Czech Republic; 2Department of Psychiatry, University Hospital Brno, Brno, Czech Republic; 3CEITEC – Central European Institute of Technology, Masaryk University, Brno, Czech Republic; 4Institute of Biostatistics and Analyses, Masaryk University, Brno, Czech Republic; 5Institute of Forensic Medicine, St. Anne’s University Hospital, Masaryk University, Brno, Czech Republic Introduction: Therapeutic drug monitoring (TDM) of clozapine is a very useful method for verifying both the correct intake and the interindividual variability of its metabolism, thereby avoiding the risk of toxicity. The purposes of this paper were to discover how many patients using clozapine in common clinical practice have clozapine plasma concentration (PC) levels in the proposed reference range and to identify factors that influence clozapine PC levels. Methods: Our study included 100 inpatients (diagnosed with schizophrenia or schizoaffective disorder) taking standard doses of clozapine (100–700 mg/day). Clozapine concentration was measured by high-performance liquid chromatography. Correlations between doses and PC levels and the influence of smoking and gender on clozapine PC levels were calculated. Results: A large number of the patients (67%) had PC levels outside the proposed reference range. The clozapine PC levels were influenced by dose, gender, and cigarette smoking. Conclusion: The correlations between dose, gender, and cigarette smoking and clozapine PC levels highlighted by our study overlap other research. It was surprising to find such a large number of patients with clozapine PC levels outside the therapeutic range. This result suggests the importance of clozapine TDM due to misunderstood inter- and/or intraindividual variability or misestimated partial therapeutic compliance. Keywords: therapeutic drug monitoring, plasma levels, interindividual variability, schizophrenia, schizoaffective disorde

Influence of dose, gender, and cigarette smoking on clozapine plasma concentrations [Corrigendum]

Mayerova M, Ustohal L, Jarkovsky J, et al. Neuropsychiatr Dis Treat. 2018;14:1535–1543. On page 1539, “Clozapine doses and clozapine PCs” section, second paragraph, line 2, the following sentence was incorrect: “The clozapine PC levels of 67% of patients were outside the proposed reference range (proposed reference range 350–600 ng/mL);28 the levels of 43% were above and 24% of patients had levels below the proposed reference range.” The correct sentence is: “The clozapine PC levels of approximately67% of patients were outside the proposed reference range (proposed reference range 350–600 ng/mL);7 42% of patients had levels below and 25% of patients had levels above the proposed reference range.”On page 1541, “Discussion” section, first paragraph, line 2, the following sentence was incorrect: “In contrast to the study by Couchman, in which more PC levels were below the proposed reference range (42.5% under and 28.4% above), in our study more PC levels were above (43% above and 24% under).”The correct sentence is: “In agreement with the study by Couchman, in which more PC levels were below the proposed reference range (42.5% below and 28.4% above), our study also found more PC levels below (42% below and 25% above).” Read the original articl

Efficacy of oral versus long-acting antipsychotic treatment in patients with early-phase schizophrenia in Europe and Israel: a large-scale, open-label, randomised trial (EULAST)

Background: Schizophrenia is a severe psychiatric disorder with periods of remission and relapse. As discontinuation of antipsychotic medication is the most important reason for relapse, long-term maintenance treatment is key. Whether intramuscular long-acting (depot) antipsychotics are more efficacious than oral medication in preventing medication discontinuation is still unresolved. We aimed to compare time to all-cause discontinuation in patients randomly allocated to long-acting injectable (LAI) versus oral medication. Methods: EULAST was a pragmatic, randomised, open-label trial conducted at 50 general hospitals and psychiatric specialty clinics in 15 European countries and Israel. Patients aged 18 years and older, with DSM-IV schizophrenia (as confirmed by the Mini International Neuropsychiatric Interview 5 plus) and having experienced their first psychotic episode from 6 months to 7 years before screening, were randomly allocated (1:1:1:1) using block randomisation to LAI paliperidone, LAI aripiprazole, or the respective oral formulations of these antipsychotics. Randomisation was stratified by country and duration of illness (6 months up to 3 years vs 4 to 7 years). Patients were followed up for up to 19 months. The primary endpoint was discontinuation, regardless of the reason, during 19 months of treatment. We used survival analysis to assess the time until all-cause discontinuation in the intention-to-treat (ITT) group, and per protocol analyses were also done. This trial is registered with ClinicalTrials.gov, NCT02146547, and is complete. Findings: Between Feb 24, 2015, and Dec 15, 2018, 533 individuals were recruited and assessed for eligibility. The ITT population included 511 participants, with 171 (33%) women and 340 (67%) men, and a mean age of 30·5 (SD 9·6) years. 410 (80%) of 511 participants were White, 35 (7%) were Black, 20 (4%) were Asian, and 46 (9%) were other ethnicity. In the combined oral antipsychotics treatment group of 247 patients, 72 (29%) patients completed the study and 175 (71%) met all-cause discontinuation criteria. In the combined LAI treatment arm of 264 patients, 95 (36%) completed the study and 169 (64%) met the all-cause discontinuation criteria. Cox regression analyses showed that treatment discontinuation for any cause did not differ between the two combined treatment groups (hazard ration [HR] 1·16, 95% CI 0·94–1·43, p=0·18). No significant difference was found in the time to all-cause discontinuation between the combined oral and combined LAI treatment groups (log rank test χ2=1·87 [df 1]; p=0·17). During the study, 121 psychiatric hospitalisations occurred in 103 patients, and one patient from each of the LAI groups died; the death of the patient assigned to paliperidone was assessed to be unrelated to the medication, but the cause of other patient's death was not shared with the study team. 86 (25%) of 350 participants with available data met akathisia criteria and 70 (20%) met parkinsonism criteria at some point during the study. Interpretation: We found no substantial advantage for LAI antipsychotic treatment over oral treatment regarding time to discontinuation in patients with early-phase schizophrenia, indicating that there is no reason to prescribe LAIs instead of oral antipsychotics if the goal is to prevent discontinuation of antipsychotic medication in daily clinical practice. Funding: Lundbeck and Otsuka