(271) Discontinuation of long-acting injectable versus oral antipsychotics in US patients with schizophrenia: a new-user survival analysis

Background: : The American Psychiatric Association suggests the use of long-acting injectable (LAI) antipsychotics for patients with schizophrenia if they have a history of poor adherence. As most LAI antipsychotics require administration only every 2 weeks to 3 months, treatment discontinuation may possibly be reduced compared to daily oral administration. However, LAI antipsychotics are still underutilized in the US, and the costs are still high. With newer LAI antipsychotics available on the market in recent years, there is a critical need to evaluate the benefits of LAI antipsychotics in contrast to oral antipsychotics.

Objective: : To compare discontinuation rates between LAI and oral antipsychotics in new users diagnosed with schizophrenia.

Methods: : This study was a survival analysis with a new-user design using Merative MarketScan claims data in the US from 2020 to 2022. Patients aged 18 years or over with a diagnosis of schizophrenia or schizoaffective disorder and at least one prescription of an LAI or oral antipsychotic initiated after a six-month washout period were included. Inverse probability of treatment weighting (IPTW) was used to control for confounders including age, sex, geographic region, urban residence, psychiatric and somatic comorbidities. Time to discontinuing LAI versus oral antipsychotics (defined as a 90-day gap in days’ supply) after initiating the first antipsychotic prescription was compared using Kaplan-Meier curves. Cox proportional hazards model estimated the hazard ratio, with additional adjustment for Elixhauser readmission score and number of therapeutic drug classes. Subgroup analyses were also conducted to exclude patients on clozapine, first-generation antipsychotics, or both.

Results: : 2,936 patients were included, of which 183 were using LAI antipsychotics, and 2,753 were taking oral antipsychotics. After IPTW, standardized differences of the confounders were less than 0.1, indicating a good balance between groups. Median time to discontinuation was 195 days for LAI users, while that of oral antipsychotics was 133 days. Comparing LAI versus oral antipsychotics, the hazard ratio of discontinuation was 0.786 (95% CI: 0.734-0.842), meaning that LAI users had a 21.4% lower hazard of discontinuing their antipsychotic than oral users. Subgroup analyses also showed similar hazard ratios.

Conclusions: : LAI antipsychotics have a lower hazard of discontinuation compared to oral antipsychotics. These findings support broader formulary coverage and clinical use of LAI antipsychotics to improve adherence among patients with schizophrenia.

Sponsorship:: None.