Clozapine treatment and discontinuation in Iceland: A national longitudinal study using electronic
patient records
Sammanfattning
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.