Three U.S. senators have introduced a bill that would require doctors to use prescription drug monitoring programs before they prescribe painkillers. The Prescription Drug Monitoring Act is co-sponsored by Senators Joe Manchin of West Virginia, Amy Klobuchar of Minnesota and Angus King of Maine.

Minnesota is one of the states in which doctors’ participation in prescription drug monitoring is voluntary. At a news conference Tuesday, Klobuchar said if such programs are not mandatory, some doctors who excessively prescribe opioids can go undetected, the Star Tribune reported.

“You can say you have (a monitoring system), but if you’re not putting in the prescriptions, what good is it?” she asked.