S202. PROXIMAL AND DISTAL FACTORS ASSOCIATED WITH CLOZAPINE EXPOSURE IN A SAMPLE OF TREATMENT RESISTANT AND TREATMENT RESPONSIVE SCHIZOPHRENIA PATIENTS

BACKGROUND: Clozapine is the gold standard for Treatment Resistant Schizophrenia (TRS) and its use is strongly recommended after failure of two/three antipsychotics. Nonetheless, prescribing trends do not appear to follow the global guidelines and switching to clozapine is often delayed or improper. Reasons for clozapine underuse are quite understood, whereas little is known on clozapine misuse. In fact, more stringent operative criteria to define TRS should be used in clinical practice, taking advantage of standardized assessment tools in order to avoid false TRS positive. In these perspectives, we studied the patterns of clozapine prescription in a sample of TRS and non-TRS patients, in order to identify psychopathological variables associated with lifetime exposure to clozapine. METHODS: 198 consecutive patients have been screened for eligibility criteria from 2016 until 2019 at Treatment Resistant Psychosis Centre of the University of Naples “Federico II”. Only stabilized schizophrenic patients aged between 18 and 65 were enrolled. All relevant clinical-demographic data were recorded. TRS diagnosis was based on TRRIP working group operational criteria and clear pseudo-resistance factors were excluded. Patients were subdivided into two groups: those having received or currently under clozapine treatment (eCLZ) and those never treated by clozapine (nCLZ). Patients were assessed for psychotic symptoms (PANSS), cognitive performances (BACS), neurological soft signs (NES), functional capacity (UPSA), social functioning (PSP and SLOF scales), and severity of illness (CGI-S). RESULTS: Among the patients included (92), eCLZ were 50 (54.3%), of which 20% being non-TRS. Compared to nCLZ, eCLZ had a significantly earlier age at onset, more hospitalizations, higher daily antipsychotic doses; eCLZ patients had significantly higher scores on the CGI-S, PANSS total, PANSS Negative, General Psychopathology and PAUSS subscale and, according to the Five Factor PANSS Model, higher score on Negative and Disorganization Factors; eCLZ had also more impaired Working Memory performances, higher NES Total score, lower PSP and all SLOF areas scores, except Area4. Then we use univariate and multivariate analysis to delineate predictors of clozapine exposure and to evaluate whether these factors may organize in proximal (independent) and distal (mediated) associations. We found five independently associated variables that mediate all the other ones: high antipsychotic doses, higher disease severity, suicide attempts, impaired working memory, more severe Stereotyped Thinking. DISCUSSION: While it is expected that some TRS patients might not receive clozapine, the observation that non-TRS patients had been exposed to clozapine may surprise. A possible explanation may be the lack of systematized procedure to diagnose TRS, which is often merely coincident with a nonspecific lack of response to antipsychotics. Due to mediation analysis, we further gained insights into the hierarchy of these variables’ impact on clozapine prescription and we finally compose a complex network of proximal and distal factors predicting clozapine exposure in schizophrenic patients. The above-mentioned independent variables significantly associated with clozapine exposure let intend that eCLZ patients may belong to a subset of more severely ill ones, beyond reaching the response threshold. Earlier onset patients may suffer from a more severe disease, be more prone to suicide attempts, and less responsive to antipsychotics. This result needs to be replicated in wider samples, and this relevant therapeutic issue should be further debated in order to gather robust evidence to support or discourage clozapine off-label use and misuse.