Medicare Part D, also called the Medicare prescription drug benefit, is an optional United States federal-government program to help Medicare beneficiaries pay for self-administered prescription drugs through prescription drug insurance premiums (the cost of almost all professionally administered prescriptions is covered under optional Part B of United States Medicare). Part D was originally proposed by President Bill Clinton in 1999, then by both political parties and Houses of Congress and President Bush during 2002 and 2003. The final bill was enacted as part of the Medicare Modernization Act of 2003 (which also made changes to the public Part C Medicare health plan program) and went into effect on January 1, 2006. The various proposals were substantially alike in that Part D was optional, it was separated from the other three Parts of Medicare in most proposals, and it used private pharmacy benefit managers on a regional basis to negotiate drug prices. The differences included consistent benefits nationwide in the Clinton/Democratic proposals (as opposed to multiple options in the Republican plans and the bill finally enacted) and a wide array of deductibles and co-pays (including the infamous "donut hole"); Bush's initial proposal included true catastrophic coverage for middle income seniors, but it was not in the final version and is a feature still not available in Part D.