Are all states required to participate in the Medicaid Drug Rebate Program (MDRP)? If not, is there a listing published by Medicaid indicating who is not participating?

Drug coverage under Medicaid is an optional benefit for the states. However, if a state opts to cover prescription drugs in their Medicaid program, they must participate in the MDRP.  As part of that participation in the MDRP, states are required to submit quarterly drug utilization data to CMS.  All states and the District of Columbia currently participate in the MDRP; therefore, they all submit quarterly drug utilization data to CMS.