The average Part D plan will cost seniors about $30 a month in 2012, down from $30.76 in 2011, the Department of Health and Human Services said in a release Friday.
"The Affordable Care Act is delivering on its promise of better healthcare for people with Medicare," HHS Secretary Kathleen Sebelius said.
Under the Part D program, seniors and others on Medicare can join a privately administered, government-subsidized health plan for their drug prescriptions.
The decrease in average costs predicted for 2012 would mark the second time average premiums have gone down since the program started in 2006, the Los Angeles Times reported.
Competition among private plans and the growing use of less expensive generic drugs have combined to make the program much less costly than budget analysts originally expected.