The nation’s supply of the opioid addiction medication methadone declined significantly during the pandemic, while the supply of buprenorphine increased, a new study finds.

Researchers at the RAND Corporation found the per capita supply of methadone fell 20% in the second quarter of 2020 and had not returned to 2019 levels as of June 2021, according to U.S. News & World Report. In contrast, supplies of the opioid addiction medication buprenorphine increased by 7% from the first quarter of 2020 through June 2021.

“The fact that methadone decreased, has sort of stayed down, and doesn’t really seem to have been compensated by buprenorphine is something that sends up a red flag as far as if there is a problem in some places in ensuring that patients still have access to these effective interventions,” said study lead author Dr. Bradley Stein.

Many of the states with the greatest decline in methadone were in the southern United States, the study found. The per capita supply dropped by more than 30% in Alabama, Mississippi and Nebraska, and by almost 50% in Florida and New Hampshire.