OBJECTIVES: The cost of diabetes drugs has risen steadily since 80s. The increase in out-of-pocket cost lead to a reduction in treatment adherence. This study evaluated trends in insulin prices in the period 01/01/1983-01/01/2021 and analyzed the effect of follow-on and authorized generic competition on insulin prices.

METHODS: Data of marketed insulin products was derived from the FDA, the wholesale acquisition cost from the RedBook (IBM Micromedex), and the consumer price index from the U.S. Bureau of Labor Statistics. Descriptive statistics and linear spline regression analyses were performed.

RESULTS: There were 70 insulins and analogs marketed in the U.S. in the period 01/01/1983-01/01/2021. The study analytical sample included 51 injectable insulins, including 41(80.4%) brand products, 7(13.7%) authorized generics, and 3(5.9%) follow-on insulins. The first human insulin entered the market with a WAC 30-defined daily dose (DDD) of $12.42. It increased 14.4 times to $178.44 by 1/1/2021, representing 5.4 times the CPI increase. The rest of the insulins and analogs exhibited similar price trends. We identified four statistically significant different periods (p<0.05): 1983-1999 (the prices for human insulins increased by $0.53/year); 2000-2009 ($2.32/year increase for human insulins and $6.56/year for long-acting and rapid/intermediate combination analogs); 2010-2017 ($16.60/year and $22.37/year increase for insulins and analogs, respectively); and 2018-2020($2.40/year decrease for human insulins, and $5.00/year increased for analogs). These price trends may be related with the Medicaid Drug Rebate (1999), the Affordable Care Act (2010), and the social and political pressure on pharmaceutical companies to lower insulin prices, and the introduction of follow-on and authorized generic competition that occurred in 2018-2020.

CONCLUSIONS: Prices of insulins and analogs increased significantly above the the inflation rate from 1/1/1983 to 1/1/2021. Changes in insulin prices occurred after the Medicaid Drug Rebate enactment (1999), the Affordable Care Act (2010), and the social pressure to reduce prices and market competition in 2018-2020.