A retrospective study of intramuscular clozapine prescription for treatment initiation and maintenance in treatment-resistant psychosis. (September 2020)

• Record Type: Journal Article
• Authors: Casetta, Cecilia; Oloyede, Ebenezer; Whiskey, Eromona; Taylor, David Michael; Gaughran, Fiona; Shergill, Sukhi S.; Onwumere, Juliana; Segev, Aviv; Dzahini, Olubanke; Legge, Sophie E.; MacCabe, James Hunter
• Is Part Of: British journal of psychiatry. Volume 217:Number 3(2020)
• Page Start: 506
• Page End: 513
• Publication Date: 2020-09
• Subjects: Intramuscular clozapine, -- clozapine, -- schizophrenia, -- treatment-resistant schizophrenia, -- clozapine discontinuation; Psychiatry -- Periodicals; Psychology, Pathological -- Periodicals; 616.89005
• DOI: 10.1192/bjp.2020.115
• Languages: English
• ISSNs: 0007-1250

Abstract

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.