Medicare Prescription Drug Savings Act of 2003 - Amends part D (Voluntary Prescription Drug Benefit Program) of title XVIII (Medicare) of the Social Security Act, as added by the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, to direct the Secretary of Health and Human Services, for each year beginning with 2006, to: (1) offer a Medicare operated prescription drug plan nationally that only offers standard prescription drug coverage and access to negotiated prices, but not any supplemental prescription drug coverage; and (2) enter into negotiations with pharmaceutical manufacturers to reduce the purchase cost of covered Medicare part D drugs for eligible part D individuals, and encourage use of more affordable therapeutic equivalents. Requires the monthly beneficiary premium charged under such a plan to be uniform nationally and determined by the Secretary.