Impact of Early Nonadherence to Oral Antipsychotics on Clinical and Economic Outcomes Among Patients with Schizophrenia

Abstract

To quantify early nonadherence to antipsychotic medications in patients with schizophrenia and its impact on short-term antipsychotic adherence, healthcare utilization, and costs. Patients who initiated oral antipsychotic treatment between January 1, 2006 to September 30, 2009 were identified from the MarketScan® Commercial Claims and Encounters (CCE) database (Truven Health Analytics, Ann Arbor, Michigan, USA). Patients were required to have a diagnosis of schizophrenia determined by the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) code 295.x, be 13-65 years of age, and have ≥ 12 months of continuous coverage prior to and after (follow-up) the earliest antipsychotic usage (index event). Medication discontinuation was defined as a gap of 30 days in available therapy; early nonadherence was defined as having the gap 90 days from the index event. During the follow-up period, medication adherence was estimated with quarterly medication possession ratios (MPR), and all-cause and schizophrenia-related healthcare resource utilization and costs were determined. The mean time to discontinuation (TTD) was 39.5 ± 20.1 days for early nonadherence patients (n = 873) and 250.7 ± 103.3 days for patients who were adherent early (n = 589). Early nonadherence resulted in more hospitalizations (0.57 vs. 0.38; P = 0.0006) with longer length of stay (LOS, 5.0 vs. 3.0 days; P = 0.0013) and higher costs ($5,850 vs. $4,211; P = 0.0244); schizophrenia-related hospitalizations, LOS, and costs were also greater. Patients that were adherent used more schizophrenia-related medications (10.4 vs. 4.7; P < 0.0001), increasing pharmacy costs ($3,684 vs. $1,549; P < 0.0001). Early nonadherence was correlated with lower drug adherence at each quarter of the follow-up period. Approximately 60% of patients with schizophrenia are nonadherent to antipsychotic medication early in treatment and are less likely to be adherent later. Early nonadherence resulted in more all-cause and schizophrenia-related hospitalizations with a greater LOS and cost of care.