Effects of prescription drug coverage restrictions on inhaled and oral corticosteroid use in a Medicare population with asthma

Background: Medicare patients face prescription drug benefit restrictions, including uncovered periods and limits on the drugs covered. For patients with persistent asthma, inhaled corticosteroids (ICS), which have no generic formulations, are a mainstay of disease control; however, some Medicare patients lack coverage for these drugs under benefits limited to generic drugs. We examined changes in steroid use in Medicare Advantage beneficiaries after the introduction of generic-only coverage.

Methods: Subjects were age 65+, with asthma, ongoing ICS treatment, and no chronic obstructive pulmonary disorder (n=2,908). In 2004 74% switched to generic-only coverage (restricted coverage), 26% had $15-25 brand copayments in 2003-2004 (unrestricted coverage), and 9% overall had high-risk asthma. We examined changes in ICS use, as well as oral corticosteroids (OCS), a powerful but non-specific treatment option for patients with moderate-to-severe asthma exacerbations. We measured changes in ICS and OCS use by the days-supply dispensed. We adjusted for individual patient characteristics.

Results: Among patients without high-risk asthma, restricted coverage patients reduced their ICS use from 2003-2004 by 10 days-supply [95% CI: -17.3, -2.6] more than unrestricted coverage patients. Among high-risk asthma patients, coverage-related reductions were greater (-22.6 days-supply [-46.5, 1.3]). High-risk patients with restricted coverage also experienced increases in OCS use compared with unrestricted coverage patients (14.8 days-supply [1.2, 28.4]).

Conclusions: Patients reduced their ICS use in response to drug coverage limitations. High-risk asthma patients had greater use of oral corticosteroids, an indication of serious asthma exacerbations. New Part D drug plans should offer continuous coverage for all medically necessary drugs.