Introduction: To quantify early nonadherence to antipsychotic medications in patients with schizophrenia and its impact on short-term antipsychotic adherence, healthcare utilization, and costs.
Methods: 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.
Results: 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.
Conclusion: 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.