Administration of Intravenous Lipid Emulsion for Dextromethorphan Poisoning with Serotonin Syndrome: A Case Report

Dextromethorphan (DXM) is used to treat colds and coughs; however, it can cause central nervous system symptoms, such as severe serotonin syndrome (SS). To our knowledge, there is no specific treatment for severe DXM poisoning, and there are no reports on the clinical use of intravenous lipid emulsion (ILE) for its treatment. Herein, we report a case of severe DXM poisoning with SS that was successfully treated with ILE. An older adolescent male visited the emergency department 1 h after ingesting 4500 mg of DXM orally. Physical examination revealed generalized convulsions, muscle rigidity, mydriasis (8.0/8.0 mm), and flushed skin, with a Glasgow Coma Scale score of 8 (E3V1M4). Severe DXM poisoning with SS was diagnosed. The patient was intubated and administered midazolam for continuous convulsions and SS. Activated charcoal was also administered, and body surface cooling was performed. After an 11 h intensive care unit admission, SS with mydriasis (6.0/6.0 mm) did not improve. Subsequently, 1100 mL of 20% soybean oil was injected as an ILE. Mydriasis improved (3.5/3.5 mm) 30 min after ILE administration; simultaneously, blood DXM concentration rapidly increased approximately two-fold. After discontinuing midazolam, the patient's consciousness signs improved, and he was weaned off the ventilator. SS was cured with no recurrence of convulsions. In cases of DXM poisoning with severe central nervous system disorders, such as SS, ILE treatment can potentially be an effective therapeutic option. For oral overdose cases, where the drug may remain in the intestinal tract, measures such as administering activated charcoal should be taken before administering ILE.