Volume 45 | Number 2 | April 2010

Abstract List

Vicki Fung Ph.D., Carol M. Mangione, Jie Huang Ph.D., Norman Turk, Elaine S. Quiter, Julie A. Schmittdiel Ph.D., John Hsu M.D., M.B.A.


To compare drug costs and adherence among Medicare beneficiaries with the standard Part D coverage gap versus supplemental gap coverage in 2006.

Data Sources

Pharmacy data from Medicare Advantage Prescription Drug (MAPD) plans.

Study Design

Parallel analyses comparing beneficiaries aged 65+ with diabetes in an integrated MAPD with a gap versus no gap (=28,780); and in a network‐model MAPD with a gap versus generic‐only coverage during the gap (=14,984).

Principal Findings

Drug spending was 3 percent (95 percent confidence interval [CI]: 1–4 percent) and 4 percent (CI: 1–6 percent) lower among beneficiaries with a gap versus full or generic‐only gap coverage, respectively. Out‐of‐pocket expenditures were 189 percent higher (CI: 185–193 percent) and adherence to three chronic drug classes was lower among those with a gap versus no gap (e.g., odds ratio=0.83, CI: 0.79–0.88, for oral diabetes drugs). Annual out‐of‐pocket spending was 14 percent higher (CI: 10–17 percent) for beneficiaries with a gap versus generic‐only gap coverage, but levels of adherence were similar.


Among Medicare beneficiaries with diabetes, having the Part D coverage gap resulted in lower total drug costs, but higher out‐of‐pocket spending and worse adherence compared with having no gap. Having generic‐only coverage during the gap appeared to confer limited benefits compared with having no gap coverage.