OBJECTIVES

To identify the effects of using extended-release (XR) medications on adherence, HbA1C control and diabetes-related hospitalizations among patients prescribing oral antidiabetic agents.

METHODS

: Using a commercial claims database, we identified 29,969 patients, who prescribed either XR or non-XR formulations of Metformin or Glipizide, for at least a year from 2011 to 2012. We measured adherence from first fill till 12/31/2012, changes in HbA1C before and in 2013, and count of diabetes-related hospital admissions in 2013.

We first used multivariate regressions to model the relationship between XR formulation and adherence, changes in HbA1C and count of hospital admissions, controlling for patients’ sociodemographic characteristics and comorbidities.

To address self-selection into XR formulations, we built a two-stage endogenous binary variable model (EBVM), which first modeled patients’ formulation choice. Our plausibly exogenous instrumental variable for XR use was the relative out-of-pocket cost of XR versus non-XR medications in each insurance plan in 2011 and 2012.

RESULTS

: After adjustment, patients prescribing XR formulations had improved adherence (78.4% vs. 75.8%, P < 0.01) and a lower count of hospital admissions in 2013 (0.054 vs. 0.068 per person, p < 0.01). XR users had larger decreases in HbA1C than Non-XR users (-0.10% vs. -0.17%), though statistically insignificant.

Our EBVM model indicates that if all patients were using XR formulations in our sample, adherence would improve by 5.1% (81.6% vs. 76.5%, p < 0.01), the annual count of diabetes-related hospitalization decrease by 50% (0.032 vs. 0.063, p < 0.01), and HbA1C would decrease by 1.50% more (-1.66% vs. -0.15%, p < 0.01).

Based on the model predictions and costs from claims, on an individual level, using XR formulations incurred an additional annual cost of $33.55, but saved $470.08 through reduced hospitalizations.

CONCLUSIONS

: Extended-release medications improve patients’ adherence, lowers HbA1c, and reduces diabetes-related hospitalizations. Extended-release medications can generate significant social value.