Medicare Rx Drug Discount and Security Act of 2003

Medicare Rx Drug Discount and Security Act of 2003 - Amends title XVIII (Medicare) of the Social Security Act (SSA) to add a new part D (Voluntary Medicare Prescription Drug Discount and Security Program). Establishes, within the Centers for Medicare and Medicaid Services of the Department of Health and Human Services (HHS), a Center for Medicare Prescription Drugs, headed by a Director of Medicare Prescription Drugs, to administer the Voluntary Medicare Outpatient Prescription Drug Discount and Security Program. Directs the Secretary of HHS to establish this Program, under which an eligible beneficiary may voluntarily enroll in a prescription drug card plan offered by an eligible entity and endorsed by the Secretary and receive specified benefits, including a catastrophic benefit. Outlines enrollee protections. Makes the costs of providing program benefits payable from the Medicare Federal Supplementary Medical Insurance Trust Fund.

Establishes a Medicare Competition and Prescription Drug Advisory Board.

Amends SSA title XVIII part B (Supplementary Medical Insurance) to provide for the exclusion of new part D costs from the determination of the Medicare part B monthly premium.

Revises Medicare supplemental health insurance (Medigap) requirements with respect to revision of the 1991 National Association of Insurance Commissioners Model Regulation to accord with this Act.