U.S.DepartmentofHealthandHumanServices
Office of Inspector General
Data Snapshot
July2023,OEI-05-23-00130
Part D Plans Generally Include Drugs Commonly Used By
Dual-Eligible Enrollees: 2023
Why OIG Did This Review KeyTakeaway
For dual-eligible enrolleesthat is, people enrolled in both Medicare and 
Dual-eligibleenrollees
Medicaidaccess to prescription drugs is particularly important.  Overall,they have
haveaccess to the majority 
verylow incomes andbecause they are more likely to be in poorer health than 
of commonly used drugs 
other people enrolled in Medicaretend to use more Medicare services.1 Because  in 2023 via Part D plans.
Medicare prescription drug coverage is an important tool for ensuring access to 
This is consistent with 
prescription drugs, Congressmandated that OIGstudy whether PartDformularies
OIGs findings from 
coverprescription drugscommonly usedby dual-eligible enrollees.2
previous years.  
Dual-eligible enrollees 
What OIG Did have several options if 
their plans do not cover 
For this report, we determined whether the 445 unique formularies used by the 
specific drugs; however, 
5,619PartD plansoperating in 2023cover 195of the 200drugs most commonly 
these options maybe
usedby dual-eligibleenrollees. Seethemethodology for more information about
burdensomeand do 
how wedetermined themostcommonly useddrugs. ThisisOIGsthirteenth 
not guarantee access 
annuallymandated report examining dual-eligible enrollees access to drugs under  to the drugs.
Medicare Part D.
Results
A majority of the 445 Part D plan formularies  Part D plans with premiums below the 
covered almost all (at least 97 percent) of the  regionalbenchmarkalsocoveredalmostall 
drugs most commonly used by dual-eligible  commonly used drugs.
enrollees. Similarly,among PartDplanswithpremiumsbelow 
Regardless of the plan in which they are enrolled,  the regional benchmark, a majority of formularies 
dual-eligible enrollees can expect to have access to  (92of 130)covered at least97percent of the drugs 
most drugs. commonly used by dual-eligible enrollees.
Each year, the Centers for Medicare & Medicaid 
services (CMS) establishes a premium benchmark 
for Part D plans that varies by region.3 It is 
particularlyimportantthatplanswithpremiums 
below the regional benchmark have high 
inclusionratesfor the mostcommonly useddrugs 
because:
 Dual-eligibleenrolleesdonotneedtopay
additional amounts in premiums for these
plans.4
 WhenCMSrandomly assignsdual-eligible
enrolleesto Part D plans, it assigns them to
plans with premiums below the regional
benchmark withoutconsideringtheirspecific
prescription drug needs.5
1 Results (contd)
Asmallnumber ofdrugswerecoveredby While dual-eligible enrollees have several 
fewer than 75 percent of formularies. options if their formularies do not cover specific 
drugs, these optionsrequirethemtotake
Although formularies frequently omitted eight  administrative actions and do not guarantee that
commonly used drugs in 2023, they all covered 
they can getthe drugs.
alternativedrugsinthesamerespectivetherapeutic 
classes, as CMS requires.6
Dual-eligibleenrollees haveuptothree
chances duringthefirst9monthsofthe
yearto switch to plans that cover the 
prescription drugs they require.7
Dual-eligible enrollees can use an 
exceptions and appeals process to 
request coverageofnonformulary drugs
bytheir plans.8
Dual-eligible enrollees can work with their 
prescriberstofindanalternativedrug 
covered by their plans.
Dual-eligibleenrollees canpayoutof
pocketfor the noncovered drugs.
Conclusion
When establishing formularies, Part D plans are permitted to balance Medicare enrollees needs for adequate 
prescription drug coverage against the need to contain costs for plan sponsors and for the Part D program.  
PartD plansmay omit certain drugsfrom prescription coverage inorder tocontrol costs. However, omitting 
drugs from coverage can also limit the ability of enrollees to access the prescription drugs they need.
In general, dual-eligible enrollees have access to nearly all of the most commonly used drugs via their Part D 
plan formularies in 2023. A majority of these formularies covered almost allcommonly used drugs, and only a 
small number of commonly useddrugs were not covered by mostformularies. Thesefindingsare largely 
unchanged from OIGs findings reported from 2011 through 2022.  Dual-eligible enrollees have several options 
if their formularies do not cover specific drugs, but these options may be burdensome and do not guarantee 
access to the drugs.
2 Top 200 Commonly Used Drugs*
3 Top 200 Commonly Used Drugs (contd)*
4 Methodology
We determined whether the unique formularies used by Part D plans operating in 2023 cover the prescription 
drugs most commonly used by dual-eligible enrollees.
 We used the 2020 Medicare Current Beneficiary Survey (MCBS) Cost and Use data to create a list of drugs 
with the highest utilization by dual-eligible enrollees.
 We used the February 2023 First DataBank National Drug Data File to identify the drug product information 
for the drugs with the highest utilization by dual-eligible enrollees.
 To determine the drugs most commonly used by dual-eligible enrollees, we took the following steps:
o We created a list of all drugs reported by dual-eligible enrollees surveyed in the 2020 MCBS, 
excluding territories.
o We collapsed this list to a list of drugs based on their active ingredients.
o We ranked the drugs by frequency of utilization, weighting the drug-event information from MCBS 
by sample weight.
o We selected the 200 drugs with the highest utilization by dual-eligible enrollees.
 Of the top 200 drugs, we analyzed 195 drugs for this review.  We removed four drugs not covered under 
Part D and one drug for which we were unable to confidently project use to the entire dual-eligible enrollee 
population.
 We collected from CMS the formulary data and the plan data for Part D plans operating in 2023.  The
 formulary data include Part D plans formularies for plans operating in 2023.
 We then analyzed the unique Part D plan formularies to determine their rates of inclusion of the drugs 
commonly used by dual-eligible enrollees.  We counted a drug as included in a Part D plans formulary if the 
formulary included the active ingredient.
Standards
Weconducted thisstudy inaccordance with theQualityStandards for Inspection and Evaluation issuedbythe 
Council of the Inspectors General on Integrity and Efficiency.
Acknowledgments
Jonathan Carroll servedastheproject leaderfor thisstudy. Office of Evaluation and Inspections headquarters 
staff who provided support include Robert Gibbons, Sarah Swisher, and Mike Novello.  This report was 
prepared under the direction of Laura Kordish, Regional Inspector General for Evaluation and Inspections in the 
Chicago regional office; Adam Freeman, Deputy Regional Inspector General; and Hilary Slover, Assistant 
Regional Inspector General.
Sources
1Kaiser Family Foundation, What is the role of Medicare for dual-eligible beneficiaries?, A Primer on Medicare: Key Facts About 
the MedicareProgramandthePeopleitCovers. Accessedathttps://www.kff.org/report-section/a-primer-on-medicare-what-is-the-
role-of-medicare-for-dual-eligible-beneficiaries/on April 6, 2022.
2 For the mandate, see the Patient Protection and Affordable Care Act, P.L. No. 111-148, 3313(a).  For each study, OIG has 
reviewed drug coverage under Medicare PartDfor all dual-eligible enrollees, rather than only for full-benefit dual-eligible 
enrollees as specified by the mandate.  (Under SocialSecurity Act 1935(c)(6), full-benefit dual-eligible enrollees are individuals 
who are eligible for both Medicare and full Medicaid benefits.)  Withthedataavailableforthese studies, wecouldnotconfidently
identify andseparate full-benefit dual-eligibleenrolleesandthus the drugs they usedfrom the total population of dual-
eligible enrollees.
3SocialSecurityAct1860D-14(b);42CFR 423.780(b)(2)(i).
4Medicaresubsidizesdual-eligibleenrolleespremiums,deductibles,andothercost-sharingobligationsuptoadetermined
premiumbenchmark that varies by region.  Medicare Prescription Drug, Improvement, and Modernization Act of 2003, P.L. No. 
108-173 (enacted Dec. 8, 2003), 101, Social Security Act 1860D-14.
5 Sources (contd)
5CMS randomlyassigns dual-eligibleenrolleestoaPartDplanwithpremiumsbelowthe regionalbenchmark when (1)they become
eligible for both Medicare and Medicaid but have not elected a Part D plan, (2) their current Part D plan will have a premiumabove 
the regional benchmark for the following year, or (3) the plan to which they were assigned is terminated.  CMS, Prescription Drug 
Benefit Manual (PDBM), ch.3, 40.1.4-5.  As an additional protection, Section 3305 of the Patient Protection and Affordable Care Act 
also requires that dual-eligible enrollees who are reassigned to a different plan receive a letter outlining the formulary coverage in 
their new plan for the drugs they are taking.  The Patient Protection and Affordable Care Act, P.L. No. 111-148, 3305.
6Planformularies donotgenerally havetoincludeeveryavailabledrug. Rather, tomeetCMSsformularyrequirements, they must 
include at least two drugs in each therapeutic category or class.  CMS, PDBM, ch.6, 30.2.1.
7 83Fed.Reg.16440,1651419(Apr.16,2018).
8CMS,PartsC&DEnrolleeGrievances,Organization/CoverageDeterminations,andAppealsGuidance,40-60.
6