title: Clozapine treatment and discontinuation in Iceland: A national longitudinal study using electronic patient records.
abstract: BACKGROUND
  Clozapine is the only drug approved for treatment-resistant schizophrenia. There is evidence that clozapine is underutilized.
  
  
  OBJECTIVE
  To evaluate the initiation and discontinuation of clozapine at Landspitali University Hospital in Iceland and the prevalence of antipsychotic polypharmacy in clozapine-treated patients.
  
  
  METHODS
  The study is a part of an ongoing longitudinal study of schizophrenia in Iceland. We identified 201 patients on clozapine or who have been on clozapine by using a keyword search in the electronic health records and by reviewing their medical records.
  
  
  RESULTS
  Mean age at first treatment with clozapine was 37.8 years. Mean follow-up period on clozapine was 11 years. After 20 years of treatment 71.2% of patients were still on clozapine. After one year of treatment 84.4% of patients were still receiving clozapine treatment. We estimate that 11.4% of patients with schizophrenia in Iceland are taking clozapine and that 16% have been treated with clozapine at some point. Polypharmacy is common, since nearly 2/3, 65.6%, of patients taking clozapine use at least one other antipsychotic and 16.9% are also receiving depot injections.
  
  
  CONCLUSIONS
  We need to increase the awareness of psychiatrists in Iceland with regard to treatment with clozapine, since only about half of the estimated population of patients with treatment-resistant schizophrenia in Iceland have ever been treated with clozapine. Nearly two thirds of patients who are prescribed clozapine in Iceland remain on it long-term.
authors.affiliation: a Faculty of Medicine , School of Health Sciences, University of Iceland , Reykjavik , Iceland ;|b Mental Health Services, Landspitali University Hospital , Reykjavik , Iceland ;
authors.forename: Oddur
authors.initials: O
authors.lastname: Ingimarsson
authors.affiliation: c Kings College London , UK ;|d National Psychosis Unit, Bethlem Royal Hospital, South London and Maudsley NHS Foundation Trust , London , UK.
authors.forename: James H
authors.initials: JH
authors.lastname: MacCabe
authors.affiliation: a Faculty of Medicine , School of Health Sciences, University of Iceland , Reykjavik , Iceland ;|b Mental Health Services, Landspitali University Hospital , Reykjavik , Iceland ;
authors.forename: Magnús
authors.initials: M
authors.lastname: Haraldsson
authors.affiliation: a Faculty of Medicine , School of Health Sciences, University of Iceland , Reykjavik , Iceland ;|b Mental Health Services, Landspitali University Hospital , Reykjavik , Iceland ;
authors.forename: Halldóra
authors.initials: H
authors.lastname: Jónsdóttir
authors.affiliation: a Faculty of Medicine , School of Health Sciences, University of Iceland , Reykjavik , Iceland ;|b Mental Health Services, Landspitali University Hospital , Reykjavik , Iceland ;
authors.forename: Engilbert
authors.initials: E
authors.lastname: Sigurdsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014150:Antipsychotic Agents / Q000627:therapeutic use*; D003024:Clozapine / Q000627:therapeutic use*; D015331:Cohort Studies; D057286:Electronic Health Records / Q000639:trends*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D019338:Polypharmacy; D012559:Schizophrenia / Q000188:drug therapy* / Q000453:epidemiology*; D028761:Withholding Treatment / Q000639:trends*; D055815:Young Adult
chemical_list: D014150:Antipsychotic Agents; D003024:Clozapine
keywords: Antipsychotics; Clozapine; Polypharmacy; Schizophrenia; Treatment-resistant