Date of Award

January 2021

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Joseph S. Ross


The affordability of prescription medications in the United States is a topic of scrutiny due to its influence on access and adherence to medications that may ultimately improve health outcomes. Despite attempts to curb drug costs through a variety of mechanisms, the convoluted nature in which drugs are priced makes it unclear whether such attempts help all patients better access their medications, especially those that should be taken over lengthy time periods in order to prevent complications of common chronic diseases. In this study, we examine two main analyses regarding drug pricing for common chronic diseases. In our first analysis, we examine Medicare Part D Prescription Drug files to evaluate the average costs that Medicare beneficiaries are required to pay out-of-pocket as either a dollar copayment or a percentage coinsurance. We characterized trends in the out-of-pocket costs required by Medicare prescription drug plans (PDPs) for generic drugs used for chronic diseases and compared them to the cash price of Walmart’s generic drug discount program (GDDP), which offers commonly used medications for $4 for a 30-day supply or $10 for a 90-day supply regardless of insurance status, from 2009 to 2017. In our second analysis, we investigate trends in list prices of branded medications used for common chronic conditions and existing within the same drug classes on the market contemporaneously. For our first analysis, there were 62 generic medications used to treat common chronic diseases available through Walmart’s GDDP in 2009, and 43 in 2017. Across all PDPs, the median beneficiary out-of-pocket expenditure for a 30-day supply of the GDDP-available medications for chronic diseases decreased from $5.70 (Interquartile Range [IQR], $2.55-$7.98) in 2009 to $2.00 (IQR, $0.00-$4.00) in 2017 (P<0.001) Approximately three-fifths (60.2%) of PDPs required beneficiaries to pay out-of-pocket costs higher than those of Walmart’s GDDP in 2009, but only one-third (33.4%) did so in 2017. In our second analysis, five drug classes of branded medications (direct oral anticoagulants [DOACs], SGLT-2 inhibitors, DPP-4 inhibitors, GLP-1 receptor agonists, and P2Y12 inhibitors) used for atrial fibrillation, diabetes, and ischemic heart disease were examined. From 2015 to 2020, monotonic increases in average wholesale prices for these drugs demonstrated median tau-b values for drugs within each class ranging from 0.84 for P2Y12 inhibitors to 0.98 for DOACs and SGLT-2 inhibitors. Median compound annual growth rates (CAGRs) ranged from 6.6% for DPP-4 inhibitors to 13.5% for P2Y12 inhibitors. The results of these analyses support concern for the affordability of prescriptions drugs used for several of the most common chronic conditions among adults in the United States. Although Medicare beneficiary out-of-pocket costs for commonly used generic drug prescriptions generally decreased over time, Medicare beneficiaries may still be paying more for the same drugs than they would through Walmart’s GDDP. Increased generic drug price transparency, including enforcing bans on gag clauses, is needed to ensure Medicare beneficiaries obtain drugs using the most affordable options. In addition, the lock-step increases in list prices, which are used to determine percentage coinsurances, and the lack of transparency of rebates and discounts would be expected to adversely affect patient adherence to medications and thus clinical outcomes. Policies that limit lock-step price increases, shorten patent durations, and encourage development of generic equivalents may ultimately mitigate rising drug prices.


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