Adherence, health care utilization, and costs between long-acting injectable and oral antipsychotic medications in South Carolina Medicaid beneficiaries with schizophrenia.

Background: Schizophrenia and schizoaffective disorder require long-term antipsychotic treatment with antipsychotic medications, but poor medication adherence can lead to increased health care utilization and costs. Long-acting injectable antipsychotics (LAIs) offer potential therapeutic advantages in that they require less frequent dosing and improved medication adherence. South Carolina has the highest adoption of LAIs among US states, making it an ideal population for comparing the effectiveness of LAIs vs oral antipsychotics (OAPs) in treating schizophrenia or schizoaffective disorder.

Objective: To evaluate the effect of LAIs compared with OAPs on medication adherence, health care resource utilization, and costs among South Carolina Medicaid beneficiaries with schizophrenia or schizoaffective disorder.

Methods: South Carolina Medicaid beneficiaries with at least 1 claim for an LAI or OAP between January 1, 2015, and December 31, 2018, aged 18 to 65, with at least 2 claims with diagnoses of schizophrenia or schizoaffective disorder were included. Propensity scores (PSs) were calculated using logistic regression adjusting for confounders and predictors of the outcome. We estimated the "average treatment effect on the treated" by employing PS-weighted t-tests and chi-square tests.

Results: A total of 3,531 patients met the inclusion criteria, with 1,537 (44.5%) treated with LAIs and 1,994 (56.5%) treated with OAPs. In PS-weighted analyses, the LAI cohort had a greater proportion of days covered than the OAP cohort with a 365-day fixed denominator (69% vs 64%; P < 0.0001), higher medication possession ratio with a variable denominator while on therapy (85% vs 80%; P < 0.0001), and higher persistence (82% vs 64%; P < 0.0001). The average number of inpatient visits and emergency department visits did not significantly differ between cohorts (0.28 hospitalizations, P = 0.90; 3.68 vs 2.96 emergency department visits, P = 0.19). The number of outpatient visits, including visits for medication administration, were greater in the LAI cohort (23.1 [SD 24.2]) vs OAP (16.9 [SD 21.2]; P < 0.0001); however, including the costs for medication administration visits, outpatient costs (per member) were approximately $2,500 lower in the LAI cohort (P < 0.0001). The number of pharmacy visits was greater in the OAP cohort (LAI 21.0 [SD 17.0] vs OAP 23.0 [SD 15.0]; P = 0.006). All-cause total costs were greater in the LAI cohort ($26,025 [SD $29,909]) vs the OAP cohort ($17,291 [SD $25,261]; P < 0.0001) and were driven by the difference in pharmaceutical costs (LAI $15,273 [SD $16,183] vs OAP $4,696 [SD $10,371]; P < 0.0001).

Conclusions: Among South Carolina Medicaid beneficiaries, treatment with LAIs for schizophrenia or schizoaffective disorder was associated with greater medication adherence rates. Patients using LAIs had higher drug costs and total costs, but lower outpatient and total nondrug costs compared with those using OAPs.