• Andrew Chambers, Jessica Patton, and Brandon K Wills.
• Virginia Poison Center, Division of Clinical Toxicology, United States of America; Department of Emergency Medicine, Virginia Commonwealth University Health System, Richmond, VA, United States of America.
• Am J Emerg Med. 2024 May 1; 79: 230.e1230.e2230.e1-230.e2.

BackgroundOlanzapine/Samidorphan (Lybalvi®) is a novel oral agent for the treatment of schizophrenia and bipolar I disorder. It was designed to reduce weight gain associated with olanzapine. Samidorphan is an analog of naltrexone, initially intended to treat substance use disorders by antagonizing mu, delta, and kappa opioid receptors.Case ReportWe present the case of a 36-year-old who took their first dose of olanzapine/samidorphan shortly before calling for emergency services. The patient took diphenhydramine and an epinephrine autoinjector for what they thought was an allergic reaction but continued to have symptoms. EMS reported involuntary muscle movements thought to be due to dystonia from olanzapine. In the ED, they experienced generalized muscle spasms lasting for several seconds and diaphoresis. Initially, the staff treated for a presumed dystonic reaction to olanzapine and administered diphenhydramine 25 mg IV, diazepam 2 mg IV, midazolam 5 mg IV, and benztropine 1 mg IV without improvement. It was later determined that the patient took 16 mg of buprenorphine SL daily. With this information, precipitated opioid withdrawal was felt to be the likely cause of symptoms. The patient received 16 mg of buprenorphine for an initial Clinical Opiate Withdrawal Scale (COWS) score of 11 with repeat COWS of 6. Why should an emergency physician be aware of this? Initiating olanzapine/samidorphan in the setting of chronic opioid therapy may result in precipitated opioid withdrawal. Additional SL buprenorphine may be a reasonable treatment modality.Copyright © 2024 Elsevier Inc. All rights reserved.

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