ABSTRACT
<b>Objective</b>:To report a case of serotonin syndrome induced by an interaction between fentanyl and amoxapine in a patient treated for cancer pain. <b>Case:A</b> 37-year-old woman with recurrence of cervical cancer was treated with oxycodone and etodolac for her cancer pain in the gluteal region. She developed acute abdominal pain and received emergency surgery under the diagnosis of upper gastrointestinal tract perforation.Continuous fentanyl infusion was initiated during surgery and was continued postoperatively to control postsurgical and cancer pain. The route of fentanyl was changed to transdermal patch the next day, and dose was escalated during the following days in attempt to control her gluteal pain. Eight days after the operation, amoxapine was prescribed as an adjuvant analgesic. Five days later, the fentanyl dose was further escalated to 2100μg/day. The following day, the patient developed tremors of the extremities, confusion and hallucinations, followed by fever and involuntary movements of the lower extremities. Amoxapine was discontinued and the symptoms subsided within 4 days.<b>Conclusion</b>:Co-administration of a tricyclic antidepressant and high doses of fentanyl precipitated serotonin syndrome in this patient.