Adherence, Persistence, Readmissions, and Costs in Medicaid Members with Schizophrenia or Schizoaffective Disorder Initiating Paliperidone Palmitate Versus Switching Oral Antipsychotics: A Real-World Retrospective Investigation

Introduction Long-acting injectable antipsychotic agents have been suggested to improve adherence and patient outcomes in schizophrenia or schizoaffective disorder. The purpose of this study was to assess medication use patterns (i.e., medication adherence, persistence), hospital and emergency department readmissions, and total direct medical costs of Oklahoma Medicaid members with schizophrenia or schizoaffective disorder switching from an oral antipsychotic (OAP) to once-monthly paliperidone palmitate (PP1M) or to another OAP (OAP-switch). Methods A historical cohort analysis was conducted from 1 January 2016 to 31 December 2020 among adults aged >= 18 and <= 64 years with schizophrenia or schizoaffective disorder who were previously treated with an OAP. The first claim for PP1M or a new OAP defined the study index date. Members who transitioned from PP1M to 3-month formulation (PP3M) were included (i.e., PP1M/PP3M). Proportion of days covered (PDC), 45-day treatment gaps, 30-day readmissions to hospitals or emergency department, and total direct medical costs were assessed using multivariable, machine-learning least absolute shrinkage, and selection operator (Lasso) regressions controlling for numerous demographic, clinical, mental health, and provider characteristics. Results Among 295 Medicaid members meeting full inclusion criteria, 183 involved PP1M/PP3Ms (44 PP1M cases transitioned to PP3M) and 112 involved an OAP-switch. The multivariable-adjusted odds of readmission were significantly associated with a 45-day treatment gap (p < 0.05) and non-adherence (i.e., PDC < 80%) (p < 0.05). Relative to PP1M/PP3Ms, the multivariable analyses also indicated that OAP-switch was associated with an 18.5% lower PDC, 92.3% higher number of 45-day treatment gaps, and an approximately 90% higher odds of all-cause 30-day readmission (p < 0.05). The adjusted pre- to post-index change in cost was approximately 49% lower for OAP-switches versus PP1M/PP3Ms (p < 0.001), although unadjusted post-index costs did not differ between groups (p = 0.440). Conclusion This real-world investigation of adult Medicaid members with schizophrenia or schizoaffective disorder observed improved adherence and persistence with fewer readmissions with PP1M/PP3Ms versus OAP-switches.