OBJECTIVES: Prior literature indicates long-acting injectable (LAI) antipsychotics (APs) have advantages over oral APs, including higher adherence rates and lower healthcare resource utilization. However, comparisons among individual LAI second generation antipsychotics (SGAs) have resulted in mixed findings since many studies did not adjust for confounders. This retrospective cohort study compared adherence for enrollees with schizophrenia by LAI SGA medication.

METHODS: Texas Medicaid continuously enrolled adults (18-63 years) diagnosed with schizophrenia and with ≥1 LAI SGA claim during 2015-2019 were included. The index date was the date of the first LAI SGA prescription claim. Medication adherence was measured using proportion of days covered (PDC) during the 12-month follow-up period, with PDC ≥ 0.8 representing adherence. Inverse probability of treatment weighting (IPTW) was employed to balance demographic and clinical characteristics among the LAI SGA groups. Repeated measures ANOVA and logistic regression were used to address the study objective.

RESULTS: Baseline demographic and clinical characteristics were comparable across the five LAI SGA groups after IPTW (N=4,422). Mean PDC was highest for paliperidone palmitate 3-month (PP3M)(0.91±0.20), followed by aripiprazole lauroxil 2-month (0.69±0.34), risperidone 4-week (0.64±0.34), aripiprazole monohydrate once monthly (0.63±0.33), paliperidone palmitate once monthly (PP1M) (0.62±0.33), and aripiprazole lauroxil once monthly (0.57±0.33). The majority (86.9%) of PP3M recipients were adherent—a significantly higher proportion than the other LAI SGA groups (aripiprazole lauroxil 2-month, 60.2%; risperidone 4-week, 44.8%; aripiprazole monohydrate, 44.3%; PP1M, 41.3%; aripiprazole lauroxil once monthly, 33.4%;p≤0.01).

CONCLUSIONS: While results of previous research were inconclusive, this large observational real-world study showed that 3-month administration frequency was superior regarding LAI SGA adherence. There were no significant differences regarding 1- or 2-month administration frequencies.