Medicare Prescription Drug Act of 2000 - Amends title XVIII (Medicare) of the Social Security Act (SSA) to add a new part D (Prescription Drug Benefit for the Aged and Disabled) outlining the following program components: (1) establishment of a voluntary insurance program, administered by the Director of the Office of Personnel Management, to provide prescription drug benefits for individuals who are aged or disabled or have end-stage renal disease and who elect to enroll under such program, to be financed from enrollee premium payments together with contributions from Federal appropriations; (2) scope of benefits; (3) payment of benefits and benefit limits; (4) eligibility and enrollment; (5) monthly premium rates; (6) special eligibility, enrollment, and co-payments rules for low-income individuals; (7) creation within the Federal Supplemental Medical Insurance Trust Fund of the Prescription Drug Insurance Account for payments; (8) administration of benefits through benefit managers; (9) authorization for the Employer Incentive Program to encourage employers to provide adequate prescription drug benefits to retired individuals by subsidizing, in part, the sponsor's cost of providing coverage under qualifying plans; and (10) authorization of appropriations to the Account to cover Government contributions.

Directs the Secretary to conduct a study on the feasibility and advisability of establishing an annual open enrollment period under the new part D program.

Amends SSA title XIX (Medicaid) to: (1) provide for coverage for certain low-income individuals of part D premiums; (2) require State Medicaid plans to provide that in the case of any individual whose eligibility for medical assistance is not limited to Medicare or Medicare drug cost-sharing, and for whom the State elects to pay monthly premiums under part D, the State will purchase all prescription drugs, without regard to whether the benefit limit for such individual has been reached; and (3) require Government payment of Medicare drug cost-sharing for qualified Medicare beneficiaries and for Medicare-eligible individuals with incomes between 100 and 150 percent of the Federal poverty line.

Directs the Medicare Payment Advisory Commission (MEDPAC) to study and report to Congress on: (1) the ability of benefit managers to improve quality and reduce costs and to assume risk; (2) strategies to improve risk assumption by such managers; (3) the likely effect of allowing benefit managers to vary aspects of the benefit packages based on costs, utilization, and access; and (4) the use of the stop-loss provision, including analysis of benefit manager data on beneficiary utilization and the effectiveness of cost constraints once the stop-loss is triggered.