Undoubtedly, you’ve received questions from your patients and staff about what Medicare Part D is and how it works. This transition has many scratching their heads, so to help clarify it, we condensed the following basic information provided by the Centers for Medicare & Medicaid Services (CMS) and the Social Security Administration (SSA) for you to share with patients and coworkers: When did it take effect? Medicare Part D is part of the Medicare Prescription Drug, Improvement and Modernization Act of 2003, which President Bush signed into law on December 8, 2003. The Medicare Part D benefit, which provides prescription drug coverage for Medicare beneficiaries, took effect January 1, 2006. Open enrollment for this program began November 15, 2005, and continues through May 15, 2006.