Antipsychotic Adherence Over Time Among Patients Receiving Treatment for Schizophrenia: A Retrospective Review

Marcia Valenstein, M.D., M.S.; Dara Ganoczy, M.P.H.; John F. McCarthy, Ph.D.; Hyungjin Myra Kim, Sc.D.; Todd A. Lee, Pharm.D., Ph.D.; and Frederic C. Blow, Ph.D.

Objective: Approximately 40% of patients with schizophrenia are poorly adherent to their antipsychotics at any given time. However, little is known about patients' adherence over time, although this has important services implications. We examined antipsychotic adherence over 4 years at the aggregate and the individual level among a large cohort of patients.

Method: We identified 34,128 Veterans Affairs patients who received a schizophrenia diagnosis and an antipsychotic fill in fiscal year (FY) 1999, completed schizophrenia visits in each of the next 4 years (FY2000, FY2001, FY2002, FY2003), and had valid medication possession ratios (MPRs) in each of these years. We examined whether patients had consistently good adherence (MPRs >= 0.8 in all 4 years), consistently poor adherence (MPRs < 0.8 in all years), or inconsistent adherence. We examined predictors of consistently poor or inconsistent adherence.

Results: The cross-sectional prevalence of poor adherence among the patient population remained stable over time; 36%-37% were poorly adherent in each year. However, 61% of patients had adherence difficulties at some point over the 4-year period. Approximately 18% had consistently poor adherence, 43% were inconsistently adherent, and 39% had consistently good adherence. Patients who were younger and nonwhite, with a substance use diagnosis, a psychiatric hospitalization, or predominant treatment with first-generation antipsychotics, were more likely to have consistently poor adherence.

Conclusions: Antipsychotic adherence is not a stable trait; most patients have difficulties with adherence over time. Health organizations and clinicians must emphasize adherence-enhancing interventions that can be provided on a longer term basis to the majority of patients.

(J Clin Psychiatry 2006;67:1542-1550)

Received Feb. 9, 2006; accepted May 10, 2006. From the Department of Veterans Affairs, Ann Arbor Center of Excellence (COE), Serious Mental Illness Treatment Research and Evaluation Center (SMITREC), Ann Arbor, Mich. (Drs. Valenstein, McCarthy, Kim, and Blow and Ms. Ganoczy); the Department of Psychiatry, University of Michigan, Ann Arbor (Drs. Valenstein, McCarthy, and Blow); the Center for Statistical Consultation and Research, University of Michigan, Ann Arbor (Dr. Kim); and the Department of Veterans Affairs, Midwest Center for Health Services and Policy Research, Hines VA Hospital, Hines, Ill., and Northwestern University Feinberg School of Medicine, Chicago, Ill. (Dr. Lee).

This research was supported by grants from the U.S. Department of Veterans Affairs, Health Services Research and Development Service: RCD 98-350 and IIR 01-174-01 to Dr. Valenstein, MRP 03-320 to Dr. McCarthy, and TXI 01-014 to Dr. Blow. The research was also supported by the Serious Mental Illness Treatment Research and Evaluation Center, Ann Arbor, Mich.

In the spirit of full disclosure and in compliance with all ACCME Essential Areas and Policies, the faculty for this CME article were asked to complete a statement regarding all relevant financial relationships between themselves or their spouse/partner and any commercial interest (i.e., a proprietary entity producing health care goods or services consumed by, or used on, patients) occurring within at least 12 months prior to joining this activity. The CME Institute has resolved any conflicts of interest that were identified. The disclosures are as follows: Drs. Valenstein, McCarthy, Kim, Lee, and Blow and Ms. Ganoczy have no personal affiliations or financial relationships with any proprietary entity producing health care goods or services to disclose relative to the article.

The views expressed in this article are those of the authors and do not represent the views of the U.S. Department of Veterans Affairs.

Corresponding author and reprints: Marcia Valenstein, M.D., M.S., SMITREC/Department of Veterans Affairs, Ann Arbor Center for Excellence, P. O. Box 130170, Ann Arbor, MI 48113-0170 (e-mail: marciav@umich.edu).