Over the past nine years, Medicare spending on EpiPens has increased by 1,151 percent, even though the total number of EpiPen users has grown by 164 percent.

The findings from the nonpartisan Kaiser Family Foundation comes amid widespread anger over a 400 percent price hike for the allergy drug from 2007, the year that generic maker Mylan acquired it. The data comes a day before a major hearing of the House Oversight Committee that is expected to include testimony from Mylan CEO Heather Bresch.