A new clinical trial will compare the ability of patients to remain in treatment for opioid addiction when prescribed buprenorphine or methadone in an office setting, STAT reports.

Since fentanyl has become more widespread in the United States, many people seeking treatment for opioid addiction have found that methadone is the only medication effective at easing cravings and withdrawal, the article notes. Many patients find that buprenorphine treatment leads to intolerable withdrawal symptoms.

“While we do have hints from the scientific literature that methadone has better outcomes with respect to retention in treatment and decreases in illicit drug use, we actually don’t have that literature in patients who are primarily using fentanyl,” said lead researcher David Fiellin, the director of Yale Medical School’s Program in Addiction Medicine.

Past studies comparing methadone and buprenorphine have included patients who were already in stable recovery when the trial began. The new study will be the first to focus on patients who have not yet entered treatment. The lead investigators are selecting six sites for the study. Results are not expected for several years.