Placement of selected new FDA-approved drugs in Medicare Part D formularies, 2009-2013

To assess formulary decisions by Part D plans for selected newly approved drugs.

Retrospective cohort study.

Formulary placement and restrictions were identified for 33 drugs in 8 therapeutic classes (antihyperglycemics, anticoagulants, antiplatelets, disease-modifying agents for multiple sclerosis [MS] and rheumatoid arthritis [RA], chronic obstructive pulmonary disease [COPD] drugs, antiepileptics, and antipsychotics) in 863 Part D plans with continuous CMS contracts between 2009 and 2013. Multivariable models estimated the impact of drug characteristics and Part D plan characteristics on probability of drug adoption and, for adopters, evaluated factors associated with months to adoption and requirements for prior authorization (PA) or step therapy (ST).

First Part D formulary placements varied from 2 to 14 months post FDA approval. On average, 56.7% of plans placed each drug within 6 months and 64.1% placed within 1 year of the National Drug Code assignment date. The most rapid adoption was for antipsychotics and antiepileptics. The slowest was for COPD drugs. More than 90% of disease-modifying agents for MS and RA were subject to PA. ST was uncommon except for antihyperglycemic agents. In adjusted analyses, enhanced benefit plans had a 4% higher probability of formulary placement (P <.01), and each additional star in the CMS star rating system increased the probability of adoption by 4% (P <.01). Overall, Medicare Advantage prescription drug plans had higher placement rates due to greater reliance on enhanced plan offerings and higher star ratings.

We found significant heterogeneity in formulary placement and restrictions for 33 new drugs in the Part D marketplace between 2009 and 2013. Further research is necessary to determine whether this pattern applies to other drug classes.