A retrospective study of intramuscular clozapine prescription for treatment initiation and maintenance in treatment-resistant psychosis

Casetta, Cecilia, Oloyede, Ebenezer, Whiskey, Eromona, Taylor, David Michael, Gaughran, Fiona, Shergill, Sukhi S., Onwumere, Juliana, Segev, Aviv, Dzahini, Olubanke, Legge, Sophie E. and MacCabe, James Hunter 2020. A retrospective study of intramuscular clozapine prescription for treatment initiation and maintenance in treatment-resistant psychosis. British Journal of Psychiatry 217 (3) , pp. 506-513. 10.1192/bjp.2020.115

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Abstract

Background Clozapine is uniquely effective in treatment-resistant psychosis but remains underutilised, partly owing to psychotic symptoms leading to non-adherence to oral medication. An intramuscular formulation is available in the UK but outcomes remain unexplored. Aims This was a retrospective clinical effectiveness study of intramuscular clozapine prescription for treatment initiation and maintenance in treatment-resistant psychosis over a 3-year period. Method Successful initiation of oral clozapine after intramuscular prescription was the primary outcome. Secondary outcomes included all-cause clozapine discontinuation 2 years following initiation, and 1 year after discharge. Discontinuation rates were compared with a cohort prescribed only oral clozapine. Propensity scores were used to address confounding by indication. Results Among 39 patients prescribed intramuscular clozapine, 19 received at least one injection, whereas 20 accepted oral clozapine when given an enforced choice between the two. Thirty-six (92%) patients successfully initiated oral clozapine after intramuscular prescription; three never transitioned to oral. Eight discontinued oral clozapine during the 2-year follow-up, compared with 83 out of 162 in the comparator group (discontinuation rates of 24% and 50%, respectively). Discontinuation rates at 1-year post-discharge were 21%, compared with 44% in the comparison group. Intramuscular clozapine prescription was associated with a non-significantly lower hazard of discontinuation 2 years after initiation (hazard ratio 0.39, 95% CI 0.14–1.06) and 1 year after discharge (hazard ratio 0.37, 95% CI 0.11–1.24). The only reported adverse event specific to the intramuscular formulation was injection site pain and swelling. Conclusions Intramuscular clozapine prescription allowed transition to oral maintenance in an initially non-adherent cohort. Discontinuation rates were similar to patients only prescribed oral clozapine and comparable to existing literature.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine MRC Centre for Neuropsychiatric Genetics and Genomics (CNGG)
Publisher:	Cambridge University Press
ISSN:	0007-1250
Date of First Compliant Deposit:	2 September 2020
Date of Acceptance:	18 May 2020
Last Modified:	06 Nov 2023 18:25
URI:	https://orca.cardiff.ac.uk/id/eprint/134637

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