Effect of increased cost-sharing on oral hypoglycemic use in five managed care organizations: how much is too much?

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BACKGROUND

For patients with a chronic disease, increased cost-sharing for medications may lead to unintended consequences, including reduced use of medications essential for control of their disease.

OBJECTIVE

The objective of this study was to estimate the effects of small ($1-6 per 30-day supply), moderate ($7-10), and large (>$10) increases in medication cost-sharing on 12-month trends in oral hypoglycemic (OH) use among adults with type 2 diabetes.

METHODS

We conducted a quasiexperimental study using a time series with comparison group design. Data were obtained from computerized membership, benefit, and pharmacy dispensing data of 5 managed care organizations (MCOs). A total of 13,110 12-month episodes of OH use and a medication cost-sharing increase ("intervention") were matched with 13,110 that had no increase. The dependent variable was OH average daily dose (ADD) standardized to each episode's mean OH ADD in the 6-month preintervention period. The principal independent variable was change in cost per 30-day OH supply between the 6-month pre- and postintervention periods. Effects of changes in cost-sharing on OH ADD were estimated using segmented time series regression.

RESULTS

Episodes with >$10 increase in cost-sharing had significantly (alpha=0.05) decreased OH ADD in the postintervention period. At 6 months after this increase, OH ADD had decreased by 18.5% from that predicted from the preintervention trend. Episodes with a $1 to $10 increase in cost-sharing and those with no increase in cost-sharing had significant linear increases in OH use over the 12-month period.

CONCLUSIONS

Large increases in medication cost-sharing were associated with immediate and persistent reductions in OH use. Small and moderate increases had little effect on OH use in the 6-month period after the increase.

Abbreviation
Med Care
Publication Date
2005-10-01
Volume
43
Issue
10
Page Numbers
951-9
Pubmed ID
16166864
Medium
Print
Full Title
Effect of increased cost-sharing on oral hypoglycemic use in five managed care organizations: how much is too much?
Authors
Roblin DW, Platt R, Goodman MJ, Hsu J, Nelson WW, Smith DH, Andrade SE, Soumerai SB