Senator Chuck Grassley (R-IA) says that taxpayers overpaid for Mylan's (MYL) - Get Report EpiPen allergy medication by $1.27 billion.

Grassley, the chairman of the Judiciary Committee, today received an estimate from the Department of Health and Human Services Office of Inspector General saying taxpayers were overpaying for the EpiPen between 2006 and 2016.

Grassley is said to be pushing Mylan and the Centers for Medicare and Medicaid Services for documents and answers explaining why EpiPen was misclassified under the Medicaid Drug Rebate Program, which resulted in overcharges to states and taxpayers.

"High prescription drug prices are a major concern across the country. I'm working to advance legislation that would help, including bills to bring more lower cost generic drugs to the market. As part of bringing down drug costs, we have to make sure companies that take part in federal health care programs aren't gaming the system," Grassley said.

Shares of Mylan were down by 1.24% to $38.86 on Wednesday afternoon.

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