Clinical Predictors of Response to Clozapine in Patients with Treatment Resistant Schizophrenia

Objectives Despite clozapine’s superior clinical efficacy in Treatment Resistant Schizophrenia (TRS), its adverse effects, need for periodic leukocyte monitoring, cost and variable clinical outcomes make the therapeutic decision making process difficult and mandate a clinical need to predict its treatment response. Hence, we investigated various clinical variables associated with treatment responses and adverse events of clozapine in TRS. Experimental Design We assessed socio-demographic and clinical profiles, premorbid adjustment, traumatic life events, cognition, disability, psychopathology and serum clozapine levels of 101 patients with TRS on stable dose of clozapine using the following instruments: Brief Psychiatric Rating Scale, Abnormal Involuntary Movements Scale, Addenbrooke’s Cognitive Examination—Revised, WHO Disability Assessment Scale-II, Childhood and Recent Traumatic Events Scale, and Premorbid Assessment Scale. We defined clozapine response a priori, adopted a case-control design framework and employed appropriate multivariate analyses. Principal Observations Past history of catatonia (p = 0.005), smoking more than one pack/day (p = 0.008), hyper-somnolence (p = 0.03) and cognitive dysfunction (p = 0.007) were associated with non-response to clozapine. Outcome definitions of non-response to clozapine influenced its association with clinical predictors. Conclusions Clinical variables are useful to predict response to clozapine. Smoking can be a potentially modifiable risk factor. Future longitudinal studies, investigating clinical and pharmacogenetic variables together, are desired.