Discontinuation of clozapine: a 15-year naturalistic retrospective study of 320 patients

Objective: Clozapine is underutilized in the management of treatment-resistant schizophrenia. To understand contributing factors, we analyzed the frequency and causes of clozapine discontinuations that occurred over a 15-year period in a clinical setting. Method: Data were extracted from computerized records and from mandatory termination reports for discontinuation events 1993-2007. The reasons for termination were analyzed. Results: Over half of the patients (n = 183/320; 57%) had at least one discontinuation (median time 609 days). The two most common causes for discontinuation were non-adherence (35%) and side-effects (28%). Hematological side-effects accounted for 45% of all side-effect associated discontinuations; most such patients remained eligible for clozapine treatment, and a significant fraction remained on clozapine after rechallenge. Central nervous system side-effects accounted for 35% of side-effect induced discontinuations. General factors significantly associated with discontinuation were African American race, older age at initiation of clozapine and less improvement in psychiatric symptoms. Conclusion: In addition to anticipating and addressing causes of non-adherence, psychiatrists should consider clozapine rechallenge in eligible patients and implement measures to mitigate clozapine-associated sedation, seizures, and other side-effects. Future studies should particularly address why African American and older patients may be more likely to discontinue clozapine.