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Abstract
Objective:
To examine medication adherence among Medicare Part D beneficiaries initiating oral anti-diabetic medications and explore whether there is any association of using mail-order pharmacy (vs. retail pharmacy) with better adherence in this patient population.
Research design and methods:
Using administrative pharmacy claims data, we conducted a retrospective cohort study on Medicare Part D beneficiaries who newly initiated oral anti-diabetic treatment between July 1, 2008 and December 31, 2008. Mail-order pharmacy users were matched to retail pharmacy users via propensity scoring, controlling for patient demographic and clinical characteristics. Adherence with oral anti-diabetic medications during the benefit year of 2009 was assessed using the proportion of days covered (PDC). Comparison of medication adherence between the mail-order pharmacy group and retail pharmacy group was conducted in the propensity matched sample using the paired t-tests and McNemar’s tests.
Results:
A total of 22,546 patients who initiated oral anti-diabetic medications were identified. The average PDC was 0.60 and only 41.6% of the study population attained good adherence (defined as PDC ≥ 0.8) with oral anti-diabetic medications during calendar year 2009. The matched sample included 1361 patients in each of the mail-order and retail pharmacy cohorts. Compared with the retail pharmacy group, mail-order pharmacy users demonstrated a significantly higher PDC (0.68 vs. 0.61; P < 0.001) throughout the benefit year. More patients in the mail-order pharmacy group (49.7%) attained good adherence with their oral anti-diabetic medications compared to 42.8% in the retail pharmacy group (P < 0.001).
Limitations:
The study was subject to limitations inherent in retrospective claims database analysis.
Conclusions:
Adherence with oral anti-diabetic medications among Medicare Part D beneficiaries is suboptimal. Patients using mail-order pharmacy had better adherence to oral anti-diabetic medications than those who used retail pharmacies. However, the causal relationship between mail-order pharmacy use and adherence should be further examined in a randomized study setting.
Transparency
Declaration of funding
There was no external funding for this study.
Declaration of financial/other relationships
L.Z., A.Z., K.M.S., A.S.H., B.S.C., and B.K.S. are employees of Prescription Solutions. K.M.S., A.S.H., and B.S.C. have disclosed that they are stock share-holders of the United Health Group.
Acknowledgements
The authors have disclosed that they have received no additional support or contributions from others in the preparation of this manuscript.
This study was presented in part at the 16th Annual Meeting of International Society for Pharmacoeconomics and Outcomes Research, May 21–25, 2011, Baltimore, MD, USA.