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. Aims: 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.

Keywords:

• Antipsychotics
• Clozapine
• Polypharmacy
• Schizophrenia
• Treatment-resistant

Acknowledgements

We thank Georg Vougiouklakis, Harpa Rúnarsdóttir, Sigurlaug J. Sigurðardóttir, Hrönn Scheving Guðmundsdóttir and Vilborg Kristín Gísladóttir for assistance in retrieving additional patient data, Þuríður Þórðardóttir and Ingibjörg Richter for assistance with databases, Elín Björk Héðinsdóttir for assisting with references, Ubaldo Benitez Hernandez for assistance with statistical analysis and the CRESTAR team.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Funding information

This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 279227.

J.H.M. receives salary support from the National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London. The views expressed are those of the authors and not necessarily those of the European Union, the NHS, the NIHR or the UK Department of Health.