The proportion of patients who recommence clozapine after cessation, the time taken to resume clozapine post-cessation, and distinguishing demographic and clinical characteristics of this group have been poorly researched. We evaluated these in the current study.
We retrospectively extracted selected demographic and clinical variables and clozapine treatment interruption and recommencement data up to December 2018 of a cohort of 458 patients who first commenced clozapine between 2006-2016. The study was conducted at three Australian health services.
Of the 310 (69%) patients who had at least one interruption of clozapine treatment, 170 (54.8%) did not resume clozapine and 140 (45.2%) recommenced it after the first interruption. More than half of those who recommenced did so within a month and 80% by 12 months. Cox regression analysis revealed that age was found to be significantly associated with recommencement, with a 2% decrease in the likelihood of restarting after an interruption for each year later that clozapine was initially commenced (HR=0.98 95%CI: 0.97, 0.997, p=0.02). Those who ceased clozapine due to adverse effects were less likely to restart than those who ceased due to noncompliance (HR=0.63 95%CI:0.41, 0.97, p=0.03). More time on clozapine prior to interruption increased the likelihood of restarting it, with each additional month on clozapine increasing this likelihood by 1% (HR=1.01 95%CI:1.01,1.02) p<0.001).
If the distinguishing demographic and clinical characteristics of the group identified in this study are corroborated through further research, this could further validate the need to identify treatment resistance and commence clozapine early in people with schizophrenia and provide appropriate interventions to those more at risk of permanent discontinuation of clozapine.