Senator Claire McCaskill (D-MO) is looking into the sales and marketing practices of the country's top five drugmakers as part of a larger effort to take on America's opioid crisis.

The U.S. Centers for Disease Control and Prevention says 91 Americans die every day as a result of an overdose.

"This epidemic is the direct result of a calculated sales and marketing strategy major opioid manufacturers have allegedly pursued over the past 20 years to expand their market share," the Missouri Senator said in a letter to the drug companies, Reuters notes.

McCaskill, the top Democrat on the Senate Homeland Security and Governmental Affairs Committee, has asked for internal estimates on the risk of abuse, addiction and overdose of opioids from Johnson & Johnson, (JNJ - Get Report) Mylan, Purdue Pharma, Insys Therapeutics (INSY) and Depomed. (DEPO)