A new study finds half of all buprenorphine drug treatments for opioid use disorder are prescribed by only 5% of doctors.

Researchers at the RAND Corporation analyzed data that includes about 90% of all prescriptions filled at retail pharmacies in the United States. They identified doctors who prescribed buprenorphine to treat opioid use disorder at least once between January 2017 and December 2018, UPI reports.

Earlier this year, the U.S. Department of Health and Human Services (HHS) announced new guidelines that allow doctors more flexibility in prescribing buprenorphine to treat opioid addiction. HHS eliminated the requirement that doctors obtain a special federal waiver to prescribe buprenorphine. Doctors were required to take an eight-hour course to receive the waiver.

“Given that a relatively low number of providers account for most of the buprenorphine prescribing, providing targeted support to those willing to safely treat more patients may be a more promising strategy to increase medication treatment among people struggling with opioid addiction than primarily focusing on increasing the number of new prescribers,” lead study author Dr. Bradley Stein said in a news release.