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Health Services Research & Development

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2006 HSR&D National Meeting Abstract

3083 — The Stability of Medication Adherence Among Patients with Schizophrenia

Author List:
Valenstein MA (Veterans Affairs Ann Arbor Health System)
Ganoczy D (Veterans Affairs Ann Arbor Health System)
McCarthy JF (Veterans Affairs Ann Arbor Health System)
Kim M (Veterans Affairs Ann Arbor Health System)
Lee T (Hines Veterans Health System)
Blow FC (Veterans Affairs Ann Arbor Health System)

Cross-sectionally, 30-45% of patients with schizophrenia are poorly adherent with antipsychotic medications, increasing their risks for adverse outcomes. Few studies have examined adherence over time, despite important clinical and services implications. We examined antipsychotic and service use among patients with schizophrenia over a four-year period.

Using the VA’s National Psychosis Registry, we identified 74,550 patients with treatment encounters for schizophrenia and antipsychotic medication fills in fiscal year (FY) 1999. We examined whether these patients received treatment for schizophrenia and calculated antipsychotic medication possession ratios (MPRs) for each of the next four years (FY00, FY01, FY02, and FY03). We examined the consistency of adherence among patients having both service encounters for schizophrenia and MPRs in each of the study years (n=33,975) and among patients with MPRs in all years, regardless of schizophrenia service encounters (n=52,245). We categorized patients as demonstrating consistently poor adherence, (MPRs <0.8 in all study years), consistently good adherence (MPRs always > 0.8), or inconsistent adherence. Finally, we examined predictors of consistently poor adherence.

Among patients with encounters for schizophrenia in all four years, 60% had difficulties with adherence. Only 40% demonstrated good adherence across all four years, 44% demonstrated inconsistent adherence, and 17% demonstrated poor adherence. When broader groups of patients were examined, smaller percentages demonstrated consistent adherence. Among patients with four MPRs but at least one year without service encounters for schizophrenia, only 29% showed consistently good adherence and 39% showed inconsistent adherence. Younger patients, African Americans, Hispanics, patients with substance abuse, and patients with a past psychiatric hospitalization were more likely to demonstrate consistently poor adherence.

Antipsychotic adherence does not appear to be a stable patient “trait”. Most patients with schizophrenia show inconsistent adherence over time, with the large majority (60%-70%) having difficulties over a four year period.

Study findings have implications for clinical and organizational efforts to address poor adherence. One time or time-limited efforts to improve adherence are insufficient. Clinicians must periodically address adherence with the majority of their patients. Organizational efforts to improve adherence will need to be ongoing or periodically repeated.

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