Rate of Formulary Adoption for Newly Approved Drugs in Part D Plans

Between 2009 and 2013, Medicare Part D adopted 33 new drugs within 8 therapeutic drug classes. In order to understand the formulary placement and restrictions for these newly approved FDA drugs in the Part D marketplace, a recent analysis, published in The American Journal of Managed Care, assessed formulary decisions made by Part D plans.

The researchers, led by Bruce Stuart, PhD, and colleagues, sought to understand how quickly Part D sponsors add newly FDA-approved drugs to their formularies. The researchers had three main objectives, including:

• tracking rates of formulary placement by Part D plans for each new drug selected for analysis for a minimum of 12 months following FDA approval;
• identify policies that plans adopted upon formulary placement; and,
• assess how formulary adoption decisions were influenced by characteristics of the drugs, number of competing products, and Part D plan characteristics.

The researchers conducted a retrospective cohort study in order to identify the formulary placement and restrictions for the 33 drugs within the following 8 therapeutic classes: antihyperglycemics, anticoagulants, antiplatelets, disease-modifying agents for multiple sclerosis and rheumatoid arthritis, chronic obstructive pulmonary disease (COPD) drugs, antiepileptics, and antipsychotics.

Further, the researchers observed 863 Part D plans with continuous CMS contracts between 2009 and 2013. They used multivariable models to estimate the impact of drug and Part D plan characteristics on the probability of drug adoption. For the adopters, they then evaluated factors associated with the months to adoption and requirements for prior authorization or step therapy.

“We employed two-part regression models to estimate the impact of drug and plan characteristics on formulary placement (part 1) and we identified factors expected to be associated with placement (months to formulary adoption and step therapy and prior authorization restrictions) for plans that added the drugs to their formularies (part 2),” Dr Stuart and colleagues explained.

According to the findings, Part D formulary placements varied from 2 to 14 months post FDA approval. Within 6 months, 56.7% of plans placed each drug of the National Drug Code assignment date, and 64.1% were placed within 1 year, on average.

The researchers found that the most rapid adoption was for antipsychotics and antiepileptics. They noted that the slowest adoption rate was for COPD drugs. Over 90% of disease-modifying agents for both multiple sclerosis and rheumatoid arthritis were subject to prior authorization and step therapy was uncommon for antihyperglycemic agents.

According to the adjusted analyses performed, 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). The overall findings concluded that Medicare Advantage prescription drug plans had higher placement rates due to greater reliance on enhanced plan offerings and higher star ratings.

“The role that Part D plan characteristics play in formulary adoption decisions largely met our expectations,” the researchers wrote. “Nonbenchmark plans and those offering enhanced benefits had higher uptake rates for new drugs, as did plans with higher star ratings.”

In order to determine if the pattern found in this study applies to other drug classes, further research is necessary, according to the researchers.

—Julie Gould

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