Sensitivity of medication use to formulary controls in medicare beneficiaries: a review of the literature.

BACKGROUND: Several studies have examined the impact of formulary management strategies on medication use in the elderly, but little has been done to synthesize the findings to determine whether the results show consistent trends.
OBJECTIVE: To summarize the effects of formulary controls (ie, tiered copays, step edits, prior authorization, and generic substitution) on medication use in the Medicare population to inform future Medicare Part D and other coverage decisions.
METHODS: This systematic review included research articles (found via PubMed, Google Scholar, and specific scientific journals) that evaluated the impact of drug coverage or cost-sharing on medication use in elderly (aged ≥65 years) Medicare beneficiaries. The impact of drug coverage was assessed by comparing patients with some drug coverage to those with no drug coverage or by comparing varying levels of drug coverage (eg, full coverage vs $1000 coverage or capped benefits vs noncapped benefits). Articles that were published before 1995, were not original empirical research, were published in languages other than English, or focused on populations other than Medicare beneficiaries were excluded. All studies selected were classified as positive, negative, or neutral based on the significance of the relationship (P <.05 or as otherwise specified) between the formulary control mechanism and the medication use, and on the direction of that relationship.
RESULTS: Included were a total of 47 research articles (published between 1995 and 2009) that evaluated the impact of drug coverage or cost-sharing on medication use in Medicare beneficiaries. Overall, 24 studies examined the impact of the level of drug coverage on medication use; of these, 96% (N = 23) supported the association between better drug coverage (ie, branded and generic vs generic-only coverage, capped benefit vs noncapped benefit, supplemental drug insurance vs no supplemental drug insurance) or having some drug coverage and enhanced medication use. Furthermore, 84% (N = 16) of the 19 studies that examined the effect of cost-sharing on medication use demonstrated that decreased cost-sharing was significantly associated with improved medication use.
CONCLUSION: Current evidence from the literature suggests that restricting drug coverage or increasing out-of-pocket expenses for Medicare beneficiaries may lead to decreased medication use in the elderly, with all its potential implications.