BACKGROUND: The median cost of anti-seizure medications (ASM) in the United States (U.S.) nearly doubled per person between 2006 and 2021. This increase, combined with shifts in ASM usage and the impact of the COVID-19 pandemic on drug supply chains amid rising inflation, underscored the urgent need to scrutinize ASM pricing dynamics. This study aimed to analyze the complex dynamics of ASM pricing in the U.S. over the past decade (2013-2023); this included how the entry of generic ASMs influenced the pricing of brand-name counterparts and what impacted price variations across different ASM formulations (e.g., significant inflation, the COVID-19 pandemic).
METHODS: This study utilized National Average Drug Acquisition Cost (NADAC) data from November 2013 to July 2023. We adjusted ASM prices for inflation using the Consumer Price Index for Medicinal Drugs - Seasonally Adjusted (CPI-MDS). Statistical analyses included fixed effects regressions and multivariable regression analysis to evaluate the impact of inflation, the number of medication labelers, and the COVID-19 pandemic on ASM prices.
RESULTS: Our study analyzed 23 ASMs approved by the U.S. Food and Drug Administration (FDA), which encompassed 223 oral formulations:112 brand-name and 111 generics. From 2013-2016 to 2020-2023, accounting for standard deviations (SD), the average price of brand-name ASMs increased from $8.71 (SD 5.9) to $15.43 (SD 10.7), while generic ASMs saw a slight decrease from $1.39 (SD 1.8) to $1.26 (SD 1.6). Consequently, the price gap between brand-name and generic ASMs surged from 1452.39 % to 3399.26 %. The proportion of matched brand-name and generic ASMs with a price difference of 1000 %-9999 % increased from 32.88 % (2013-2016) to 41.43 % (2020-2023), while those exceeding 10,000 % rose from 16.44 % to 20 % in the same period. Generic immediate-release (IR) formulations were significantly less expensive than extended-release (ER) or delayed-release (DR) counterparts, with cost differences reaching up to 7751.20 %. The number of medication labelers was inversely related to generic ASM prices, which decreased by 5.45 % (p = 0.001) with each additional generic labeler, while brand-name ASM prices increased by 2.46 % (p < 0.001) with each additional generic labeler. The COVID-19 pandemic led to a 24.4 % increase in brand-name ASM prices and a 23.1 % decrease in generic ASM prices.
CONCLUSIONS: The findings reveal an expanding price disparity between brand-name and generic oral ASMs. An inverse relationship was observed between the number of medication labelers and generic ASM prices, with additional labelers driving down generic prices. However, introducing more generic labelers led to a significant increase in brand-name ASM prices. Furthermore, following patent expirations, brand-name ASM prices rose-a trend explained by the "generics paradox," where, contrary to expectations, brand prices do not decrease and may even increase when generics enter the market. These findings underscore the need for targeted interventions in drug pricing policies to manage the rising costs associated with epilepsy treatment. To ensure equitable access to ASMs, stakeholders must understand and address the factors driving these pricing dynamics.