Objective: The effectiveness of clozapine is clearly superior to other antipsychotics in the treatment of refractory schizophrenia. Clozapine leads to various side effects, and therefore many patients are forced to discontinue. In this study, we analyzed the registry database of all cases in Japan to identify risk factors for discontinuation of clozapine. Methods: The Clozaril patient monitoring service® (CPMS) database from July 31, 2009 to January 26, 2020 was acquired. We defined the following exclusion criteria: patients who had ever taken clozapine by a non-CPMS method, such as an individual import or clinical trial, patients who did not receive clozapine after being enrolled in CPMS, and patients with initial doses other than 12.5 mg (outside the current protocol). Therefore, all patients in this study are new users. Multivariate Cox regression analysis was used to investigate independent risk factors associated with time to discontinuation of clozapine. Results: We identified 8,263 patients as the study population. Clozapine discontinuation was significantly associated with age 40 and older [hazard ratio (HR)=1.66, p<0.001], intolerance to olanzapine (HR=1.31, p=0.018), previous treatment with clozapine (HR=1.30, p=0.001), and leukocyte counts <6,000/mm3 (HR=1.24, p<0.001). The Kaplan-Meier curves for clozapine discontinuation by age group revealed that older age at the time of clozapine introduction tended to have lower continuation rates. Conclusion Careful administration is important because patients with these factors have a high risk of discontinuation. In addition, the initiation of clozapine during the younger period was more effective and more tolerated.

The Standardized Structured Medical record Information eXchange (SS-MIX) was started in 2006 as the project supported by the Ministry of Health, Labour and Welfare (MHLW) for promoting the exchange of the standardized medical information. Free soft wares developed in the project allow the storage of medical information to receive HL7 messages for prescription, laboratory test results, diagnoses and patient demographics in the hospital information system (HIS). We encourage the use of the SS-MIX standardized storage for postmarketing surveys and clinical studies. The recommendations consist of the following 7 parts. [1] In surveys and clinical studies, the information of drugs and laboratory test results in the SS-MIX standardized storage can be directly transferred to the electronic questionnaire and the investigators may obtain the information with high accuracy and granularity. [2] The SS-MIX standardized storage works as the backup system for the HIS because it can provide the minimum information essential in patient care even under the disastrous condition like earthquake or unexpected network failure. [3] The SS-MIX standardized storage may be useful to conduct a good pharmacoepidemiology study not only because it provides the information in the storage efficiently but also it can be used to identify “new users” who started the drug after some period of non-use.The “new user” design is often essential to have the unbiased results. [4] When the drug company conducts postmarketing surveys according to the current regulation, the use of the SS-MIX standardized storage will facilitate the fast and efficient collection of data to develop the timely measure to minimize the drug-related risk. With the SS-MIX standardized storage, it is also expected that many types of study design can be employed and the quality of data is improved in the survey. [5] The SS-MIX standardized storage maybe also useful to evaluate the risk minimization action plan by comparing the prescription pattern or incidence of the targeted adverse event between two periods before and after the implementation of the action plan. [6] In planning clinical trials, the SS-MIX standardized storage may be used to estimate the size of eligible patients. The storage may also allow conducting cross-sectional studies to know characteristics of diseases or drug treatment. In addition, cohorts of those who had coronary artery angiography, new users of a drug and those with a rare disease may be readily identified. Using such cohorts, investigators can initiate a case-control study nested within the cohort, pharmacogenomic studies and comparative effectiveness researches. [7] The SS-MIX standardized storage may be used as the formal data source in clinical trials in the future when some conditions are satisfied. For instance, the formal agreement should be reached between industry, government and academia on the use of standards of data structure in Clinical Data Interchange Standards Consortium (CDISC) and on the operation of computerized system validation (CSV) in the clinical trials.