580. Clinical treatment pathways of antipsychotics in patients with schizophrenia spectrum disorder: a retrospective longitudinal observational study

Abstract

Abstract Background Treatment of schizophrenia relies on antipsychotics. Real-world antipsychotic prescribing sequences in first-episode schizophrenia (FES) remain understudied outside clinical trials. Understanding early treatment pathways is key to personalizing care and timely clozapine use for treatment resistance. Aims & Objectives This study aims to: 1) quantify first-line antipsychotic prescriptions after a first diagnosis; 2) analyze prescribing trends over time; and 3) determine one-year clozapine initiation rates, stratified by demographics. Method Using a psychiatric hospital cohort (2014 - 2019) we identified 3054 SSD patients who had at least one year of medical records, and reconstructed their prescription pathways with the “Cohort Pathway” module; temporal trends were tested with Kendall’s τ, one-year clozapine incidence was calculated with the “Incidence Analysis” module, and baseline characteristics were summarized through the “Cohort Characteristics” module, all within ATLAS. Results The five most commonly initiated agents were quetiapine (34.4 %), olanzapine (16.6 %), aripiprazole (13.2 %), oral risperidone (10.3 %), and amisulpride (5.4 %). In the second round of switching, the top three alternatives remained within this same quintet. Quetiapine rose (τ = +0.73, p = 0.06) while risperidone fell (τ = −0.73, p = 0.06) across 2014-2019. Among children, however, aripiprazole ranked first (26.8%). Only 27 patients (15.1 per 1000 person-years) initiated clozapine within 12 months; rates were numerically higher in males and children, but the 95 % CI crossed unity. Discussion & Conclusions This analysis of antipsychotic prescribing for first-episode SSD from 2014-2019 found quetiapine, olanzapine, aripiprazole, risperidone, and amisulpride were the most common initial agents. Quetiapine use rose as the dominant choice while risperidone fell. Clozapine initiation within one year was very low (15.1/1000 person-years). The shift toward quetiapine aligns with international trends. Key limitations include potential case identification bias from using single-hospital data, lack of symptom severity information to explain prescribing patterns, and low precision for clozapine estimates. In this large, single-centre real-world cohort, quetiapine dominated both first-line and second-switch antipsychotic choices, followed by olanzapine, aripiprazole, oral risperidone, and amisulpride, yet early clozapine uptake remains rare. These sequence maps provide an evidence base for benchmarking and refining personalized, guideline-concordant prescribing pathways in SSD.