Cost-effectiveness of olanzapine long-acting injection in the treatment of patients with schizophrenia in the United States: a micro-simulation economic decision model

To compare, from the perspective of third-party payers in the United States health care system, the cost-effectiveness of olanzapine long-acting injection (LAI, depot) with alternative antipsychotic agents including risperidone-LAI, paliperidone-LAI, haloperidol-LAI, and oral olanzapine, in the treatment of patients with schizophrenia who have been non-adherent or partially adherent with oral antipsychotics. A 1-year micro-simulation economic decision model was developed to simulate the dynamics of usual care of patients with schizophrenia who continue, discontinue, switch, or restart their medication. The model uses a range of clinical and cost parameters including adherence levels, relapse with and without hospitalization, quality-adjusted life years (QALYs), treatment discontinuation rates by reason, treatment-emergent adverse events, suicide, health care resource utilization, and direct health care costs. Published medical literature and a clinical expert panel were used to develop baseline model assumptions. Key model outputs include annual total direct cost (US$$) per treatment and incremental cost-effectiveness values per additional QALY gained. Model results found that the olanzapine-LAI treatment strategy was more effective (greater QALYs) and less costly than risperidone-LAI, paliperidone-LAI, and haloperidol-LAI. In addition, olanzapine-LAI was both more effective and more costly, with an estimated incremental cost/QALY of $$26,824 compared to oral olanzapine. The base-case and multiple sensitivity analyses found olanzapine-LAI to remain within acceptable cost-effective ranges (<$$50,000) in terms of incremental cost/QALY gained. This micro-simulation model finds the olanzapine-LAI treatment strategy to result in better effectiveness and to be a cost-effective alternative compared to oral olanzapine and the LAI formulations of risperidone, paliperidone, and haloperidol in the treatment of non-adherent and partially adherent patients with schizophrenia in the United States. A key limitation is the assumption how LAI therapies compare to oral counterparts due to sparse head-to-head data. Further research is needed to verify baseline assumptions.