Affordable Medicines Utilization Act of 2011 - Amends title XIX (Medicaid) of the Social Security Act, with respect to FY2012-FY2014, to require an increase in the quarterly Medicaid payment to a state by 50% of the generic drug utilization savings amount if the state's generic substitution rate for the most recent preceding fiscal year for which data is available is greater than its rate for the most recent second preceding fiscal year for which data is available.
Directs the Secretary of Health and Human Services (HHS) to determine the state's generic substitution rate for such fiscal years.
Defines "generic substitution rate" as the share of all drug units for which Medicaid payment is made to a state for the 20 most widely prescribed multiple source drugs under the state program that have a specific National Drug Code.