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Rothendler JA, Fincke BG, Reisman JI, Christiansen CL, Miller DR, Borzecki AM, Berlowitz DR. Diabetes Control in Patients on Oral Monotherapy Regimens: Relationship to Adherence and Medication Dose. Poster session presented at: VA HSR&D National Meeting; 2008 Feb 14; Baltimore, MD.
Objectives: Many patients with diabetes mellitus (DM) have suboptimal blood sugar control, a finding that may be related to both medication non-adherence as well as insufficient intensification of medication regimens. In particular, for some individuals, monotherapy with oral medications may result in insufficient control. We sought to assess the association of diabetes control with medication adherence and medication dose levels in patients on stable monotherapy regimens. Methods: In VA patients with a recorded hemoglobin A1c (HbA1c) during 4/04-9/04, we identified 47,066 individuals who had received as monotherapy at least 5 prior 90-day fills of a hypoglycemic medication with the same daily dose. All doses were classified as either "low" or "high". We assessed "refill adherence" by a "medication possession ratio" (MPR), defined as the days' supply of medication dispensed at the first 4 fills (360 days) divided by the interval between fills 1-5. Logistic regression, accounting for age, gender and month of HbA1c, was used to determine the odds ratio of having HbA1c < 7% for MPR < 0.8 relative to reference MPR of 0.9-1.1. Results: For those on "low" vs. "high" medication doses, the overall percent with HbA1c < 7% was 77.4% vs. 61.2% (p < .0001) respectively. The odds ratio of having HbA1c < 7% with an MPR < 0.8 (compared to reference of 0.9-1.1) was 0.805 (p < .0001) and 0.855 (p = .0004) for "low" and "high" doses, respectively. However, there was variation among individual medications and doses in the association of MPR to HbA1c control, and the relationship of MPR values to HbA1c control was typically not monotonic. Implications: Patients on "high" or "low" dose monotherapy regimens with sub-optimal adherence, as reflected by MPR < 0.8, were less likely to have HbA1c < 7%. The seemingly paradoxical observation that those on higher medication doses had worse overall HbA1c control likely reflects the presence of more severe DM, so that simply increasing the medication dose while maintaining monotherapy was insufficient to control blood sugars. Impacts: Interventions that address both patient non-adherence as well as the need for adequate intensification of medications by providers are needed to improve overall DM control in the VA population.
