Encephalopathy following subcutaneous administration of Brixadi® extended-release buprenorphine.

Long-acting injectable buprenorphine is one option for the management of opioid use disorder. The United States Food and Drug Administration has approved two brands for monthly injection, Sublocade ® (Indivior, North Chesterfield, VA, USA) and Brixadi® (Braeburn, Plymouth Meeting, PA, USA). We report the development of encephalopathy following administration of Brixadi®. Consent was obtained from the patient. A 62-year-old patient with a history of current methamphetamine and prior fentanyl abuse, chronic pain due to lumbar radiculopathy presented to the emergency department with three days of altered mental status. She received subcutaneous Brixadi® 128 mg monthly formulation three days prior at an outpatient addiction medicine clinic, reportedly to treat simultaneously presumptive incidental opioid dependence from contaminated methamphetamine use due to serial positive urine fentanyl testing over the prior three visits, most recently 3 months prior, and chronic low back pain. Urine fentanyl testing on the date of presentation was negative. She developed persistent altered mentation and somnolence starting two hours after injection.