We present a case in which serotonin syndrome developed immediately after the initiation of low-dose methadone following an increase in oxycodone dose and the initiation of duloxetine. The symptoms of serotonin syndrome were alleviated and later disappeared upon cessation of methadone alone. The case was a 47-year-old woman with a desmoid tumor. The administration of duloxetine (20 mg/day) was initiated while the patient took oxycodone sustained-release tablets (40 mg/day). The following day, excessive perspiration, chills, and tremors appeared after the initiation of 15 mg/day methadone. Discontinuation of methadone led to an alleviation of the symptoms which completely disappeared 3 days later. The results suggest that low-dose methadone can trigger serotonin syndrome as early as after the first dose. Thus, it is important to be aware of the risks and to immediately take action if symptoms appear.

BackgroundChemical coping is an inappropriate method for dealing with stress through the use of opioids; it is considered the stage prior to abuse and dependence. In patients with cancer, it is important to evaluate the risk of chemical coping when using opioids. There are some pediatric opioid use-related tolerances and addictions; however, no mention of chemical coping has been found.Case presentationWe present a case of an 11-year-old Japanese boy with acute lymphocytic leukemia. After transplantation, he complained of abdominal and articular pain, which are considered as symptoms of graft-versus-host disease; thus, opioid therapy was initiated, and the dose was gradually increased for pain management, resulting in a high dose of 2700 μg/day of fentanyl (4200–4700 μg/day including the rescue dose). After switching from fentanyl to oxycodone injections, he continued to experience pain, and there was no change in the frequency of oxycodone rescue doses. Physically, his pain was considered to have alleviated; thus, there was the possibility of mental anxiety resulting in the lowering of pain threshold and the possibility of chemical coping. Mental anxiety and stress with progress through schooling was believed to have resulted in chemical coping; thus, efforts were made to reduce the boy’s anxiety, and opioid education was provided. However, dose reduction was challenging. Ultimately, with guidance from medical care providers, the opioid dose was reduced, and the patient was successfully weaned off opioids.ConclusionsWhen chemical coping is suspected in pediatric patients, after differentiating from pseudo-addiction, it might be necessary to restrict the prescription for appropriate use and to provide opioid education while taking into consideration the emotional background of the patient that led to chemical coping.