• Michael A Fischer, Margaret R Stedman, Joyce Lii, Christine Vogeli, William H Shrank, M Alan Brookhart, and Joel S Weissman.
• Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital, Boston, MA 02120, USA. mfischer@partners.org
• J Gen Intern Med. 2010 Apr 1; 25 (4): 284290284-90.

BackgroundNon-adherence to essential medications represents an important public health problem. Little is known about the frequency with which patients fail to fill prescriptions when new medications are started ("primary non-adherence") or predictors of failure to fill.ObjectiveEvaluate primary non-adherence in community-based practices and identify predictors of non-adherence.Participants75,589 patients treated by 1,217 prescribers in the first year of a community-based e-prescribing initiative.DesignWe compiled all e-prescriptions written over a 12-month period and used filled claims to identify filled prescriptions. We calculated primary adherence and non-adherence rates for all e-prescriptions and for new medication starts and compared the rates across patient and medication characteristics. Using multivariable regressions analyses, we examined which characteristics were associated with non-adherence.Main MeasuresPrimary medication non-adherence.Key ResultsOf 195,930 e-prescriptions, 151,837 (78%) were filled. Of 82,245 e-prescriptions for new medications, 58,984 (72%) were filled. Primary adherence rates were higher for prescriptions written by primary care specialists, especially pediatricians (84%). Patients aged 18 and younger filled prescriptions at the highest rate (87%). In multivariate analyses, medication class was the strongest predictor of adherence, and non-adherence was common for newly prescribed medications treating chronic conditions such as hypertension (28.4%), hyperlipidemia (28.2%), and diabetes (31.4%).ConclusionsMany e-prescriptions were not filled. Previous studies of medication non-adherence failed to capture these prescriptions. Efforts to increase primary adherence could dramatically improve the effectiveness of medication therapy. Interventions that target specific medication classes may be most effective.

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