U.S. Department of Health and Human Services. February 2, 2012.
Nearly 3.6 million people with Medicare saved $2.1 billion on their prescription drugs in 2011 thanks to the Affordable Care Act according to data issued by the Department of Health and Human Services (HHS). Savings for people with Medicare will increase over time. According to the report, the average person with Medicare will save nearly $4,200 by 2021 because of the new law.
http://aspe.hhs.gov/health/reports/2012/MedicareBeneficiarySavings/ib.pdf [PDF format, 4 pages].