1. Part D plans generally include drugs commonly used by dual eligibles: 2017 Publication: [Washington, D.C.] : U.S. Department of Health and Human Services, Office of Inspector General, June 2017 Subject(s): Dual MEDICAID MEDICARE EligibilityFormularies as TopicInsurance CoverageMedicare Part D -- statistics & numerical dataDrug UtilizationMedicare Part D -- economicsHumansUnited StatesUnited States. Department of Health and Human Services.United States.