Impact of clozapine as the mainstay therapeutical approach to schizophrenia and substance use disorder: A retrospective inpatient analysis

A retrospective study was conducted to analyze prescription pattern of clozapine in dual diagnosis inpatients' and to find out if there was any association between clozapine prescription and acute relapses either from psychiatric symptoms or from substance use disorder. All patients admitted at Lisbon's Psychiatric Hospital Center during a 4 months' period for psychiatric inpatient treatment with a dual diagnosis at discharge were selected and their clinical files were screened. From 536 patients, 17,5% had a dual diagnosis at discharge. Most frequent psychiatric diagnosis associated with substance use disorder was schizophrenia (50%), followed by major depression disorder (17%) and bipolar disorder (10,6%). Most frequent substance of abuse was alcohol, followed by cannabinoids, nicotine, cocaine, and opiates. At least one antipsychotic drug was prescribed to 85,1% patients, and clozapine was prescribed to 22,3%. There was a statistically significant association between clozapine prescription and prevention of acute relapses of psychiatric symptoms in dual diagnosis patients. Although there was no significant association between prescription of clozapine versus other antipsychotic drugs in the prevention of relapses of substance use, there was a larger than expected number of patients in clozapine that didn't have a relapse of substance use.