The cost of buprenorphine treatment for opioid use disorder decreased from 2015 to 2020, according to a new study. But costs varied widely depending on a patient’s insurance, Axios reports.

Average daily out-of-pocket costs for buprenorphine decreased overall from $4.79 in 2015 to $1.91 in 2020.

Researchers at the Centers for Disease Control and Prevention found in 2020, patients had daily average out-of-pocket costs of 10 cents for a prescription paid by Medicaid, or 46 cents for one paid by Medicare. Patients with private or commercial insurance paid an average of $1.82 for a prescription. Patients who paid for prescriptions themselves or were part of an assistance program paid the most — $8.44 and $6.31 respectively in 2020.

The price of a buprenorphine prescription varied by region. The South had the highest number of prescriptions written, as well as the greatest average cost — $2.91 daily. In the Northeast, patients paid an average daily cost of $1.04.