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The impact of switching to clozapine on psychiatric hospital admissions: a mirror-image study

  • P. Kirwan (a1), L. O’Connor (a1), K. Sharma (a1) and C. McDonald (a1)



Clozapine is an atypical antipsychotic agent used primarily in the management of treatment-resistant schizophrenia. Previous studies have demonstrated clozapine’s superior efficacy over other antipsychotic medications in treating this population of patients. The aim of this study was to assess if the number of hospital admissions and days spent in hospital reduced with the initiation of clozapine, compared with when the same sample of patients were prescribed other antipsychotics prior to clozapine initiation.


A mirror-image study design was adopted. In this case the intervention under study was the initiation of clozapine. Information was collected retrospectively from the charts of patients attending the University Hospital Galway clozapine clinic. The number of admissions and number of hospital days were collected for each patient over the 3 years before and after clozapine initiation. Wilcoxon’s signed-rank test was used to test for statistical significance.


The total sample size comprised of 62 patients, of which the majority were male (74.2%) and had a diagnosis of schizophrenia (82.3%). The mean dose of clozapine was 417 mg, and mean age of the sample was 38 years. Mean number of hospital admissions reduced from 2.8 to 0.8 (p<0.0001) following initiation of clozapine. Mean number of days spent in hospital reduced from 116.4 to 17.1 (p<0.0001).


After initiation of clozapine treatment, patients experience a substantial reduction in number of hospital admissions and number of days spent in hospital when compared with a similar period prior to clozapine initiation.


Corresponding author

*Address for correspondence: Dr Patrick Kirwan, MB, BCh, BAO, MRCPsych, MMedSc, Senior Registrar in General Adult Psychiatry, Department of Psychiatry, University Hospital Galway, Newcastle Road, Galway, H91 TK33 Ireland. (Email:


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