The Impact of the Medicare Part D Prescription Benefit on Generic Drug Use
Little information exists regarding the impact of Medicare Part D on generic drug use.
To examine changes in the use of generic prescriptions attributable to Part D among a sample of Medicare beneficiaries.
Design, participants, and measurements
Difference-in-difference analysis of pharmacy claims of Part D enrollees and non-enrollees aged 67–79 years from 2005 to 2006. The final sample represented approximately 2.4 million unique subjects. Analyses were conducted separately for major therapeutic classes, limited to subjects filling at least one prescription within the class during 2005 and 2006, and adjusted for subject characteristics, prescription characteristics, socio-demographic characteristics measured through zipcode-linked Census data, baseline differences between Part D and non-Part D enrollees, and secular trends in generic use.
Generic drugs accounted for 58% of total prescriptions. Among the entire group of beneficiaries, there was a trend of increased generic drug use in 13 out of 15 drug classes examined. However, after adjusting for potential confounders, the growth rate of generic drug use was lower among Part D enrollees than among non-enrollees; enrollees were slightly less likely to fill prescriptions for generic drugs vs. brand-name drugs in 2006 compared to 2005 (odds ratio 0.95, 95% confidence interval 0.94–0.95).
Despite secular trends of increased utilization of generic drugs among both Part D enrollees and non-enrollees, the net impact of Part D among these beneficiaries was a modest decrease in the use of generic drugs. This finding, which is consistent with economic theory but contrary to several recent reports, highlights the complexity of assessing the impact of Part D on overall consumer welfare.
KEY WORDSmedicare Part D prescription coverage pharmacoepidemiology generic drugs
- 4.Center for Medicaid and Medicare Services Press Release. Medicare drug plans strong and growing: beneficiaries compared plans and continued to sign up for prescription drug coverage. January 30, 2007. http://www.cms.hhs.gov/apps/media/press_releases.asp (Accessed July 7, 2008).
- 7.Generic drug utilization in the Medicare Part D program. Department of Health and Human Services. Office of the Inspector General. November 2007 (OEI-05–07–00130).Google Scholar
- 9.Hass JS, Phillips KA, Gerstenberger EP, Seger AC. Potential savings from substituting generic drugs for brand-name drugs: Medical Expenditure Panel Survey, 1997–2000. Ann Intern Med. 2005;142:891–7.Google Scholar
- 10.National Association of Chain Drug Stores. Available online at http://www.nacds.org/wmspage.cfm?parm1=507 (Accessed on July 7, 2008).
- 12.Bhat VN. Patent term extension strategies in the pharmaceutical industry. Pharmaceuticals Policy and Law. 2005;6:109–22.Google Scholar
- 13.Center for Medicaid and Medicare Services Press Release. Generic drug use on the rise: consumers and payers benefit as more Americans turn to generics as way to save money and improve their health. February 8, 2007. http://www.cms.hhs.gov/apps/media/press_releases.asp (Accessed July 7, 2008).
- 14.“Medicare drug plans prompt rise in generic use.” ACP Observer. 2007;27:5.Google Scholar
- 15.“Strategies to avoid Medicare’s big hole.” New York Times. November 24, 2007.Google Scholar
- 17.Stuart B, Singhal P. The stability of Medicaid coverage for low-income dually eligible Medicare beneficiaries. Kaiser Family Foundation Policy Brief. May 2006. Publication #7512.Google Scholar
- 19.Krieger N. Overcoming the absence of socioeconomic data in medical records: Validation and application of a census-based methodology. Am J Epidemiol. 1992;82:703–10.Google Scholar
- 20.Angrist J, Krueger A. “Empirical Strategies in Labor Economics,” Handbook of Labor Economics, Vol. 3, ed. by A. Ashenfelter and D. Card, Amsterdam: Elsevierss; 1999.Google Scholar
- 23.Artz MB, Hadsall RS, Schondelmeyer SW. Impact of generosity level of outpatient prescription drug coverage on prescription drug events and expenditure among older persons. American Journal of Public Health 2002;1257–63.Google Scholar
- 28.Steinberg M, Jones K. Coverage through the ‘doughnut hole’ grows scarcer in 2007. Families USA, November 2006 (Publication #06–107).Google Scholar