Measurement of treatment adherence with antipsychotic agents in patients with schizophrenia

Abstract

Xinhua S Ren1,2,3, Lawrence Herz4,5, Shirley Qian1,2,3, Eric Smith3,4, Lewis E Kazis1,2,31The Center for the Assessment of Pharmaceutical Practices (CAPP), Boston University School of Public Health, Boston, MA, USA; 2Department of Health Policy and Management, Boston University School of Public Health, Boston, MA, USA; 3Center for Health Quality, Outcomes, and Economic Research, Bedford Veterans Affairs Medical Center, Bedford, MA, USA; 4Division of Psychiatry, Boston University School of Medicine, Boston, MA, USA; 5Mental Health Service Line, Bedford VA Medical Center, Bedford, MA, USAAbstract: The importance of medication adherence in sustaining control of schizophrenic symptoms has generated a great deal of interest in comparing levels of treatment adherence with different antipsychotic agents. However, the bulk of the research has yielded results that are often inconsistent. In this prospective, observational study, we assessed the measurement properties of 3 commonly used, pharmacy-based measures of treatment adherence with antipsychotic agents in schizophrenia using data from the Veterans Health Administration during 2000 to 2005. Patients were selected if they were on antipsychotics and diagnosed with schizophrenia (N = 18,425). A gap of ≥30 days (with no filled index medication) was used to define discontinuation of treatment as well as medication “episodes,” or the number of times a patient returned to the same index agent after discontinuation of treatment within a 1-year period. The study found that the 3 existing measures differed in their approaches in measuring treatment adherence, suggesting that studies using these different measures would generate different levels of treatment adherence across antipsychotic agents. Considering the measurement problems associated with each existing approach, we offered a new, medication episode-specific approach, which would provide a fairer comparison of the levels of treatment adherence across different antipsychotic agents.Keywords: medication adherence, antipsychotic agents, schizophrenia