An autopsy case of fatal lacosamide overdose

Lacosamide is a third-generation antiepileptic drug that selectively promotes the slow inactivation of sodium channels. Herein, we report a case of fatal lacosamide poisoning following an autopsy. A female in her fifties was found dead in her living room. She had been diagnosed with epilepsy and had been prescribed lacosamide, carbamazepine, lamotrigine, and perampanel. At the scene, empty blister packs containing a total of 4950 mg of lacosamide were found in her bag. Additionally, two tablets of a commercially available sleeping medication containing diphenhydramine were missing. A medicolegal autopsy was conducted two days later. The stomach contained 120 mL of a slightly viscid fluid, which appeared powdery and suspended. Qualitative analysis using gas chromatography-mass spectrometry detected lacosamide, carbamazepine, and lamotrigine, while perampanel and diphenhydramine were not found. The blood lacosamide concentration was 70.1-86.8 µg/mL. These values were higher than the current reference range of lacosamide and comparable to or higher than those of previous fatal cases. Carbamazepine and lamotrigine levels were within or below the therapeutic range. Based on these findings, we determined that the cause of her death was lacosamide poisoning.