A 22-year-old man is brought to the emergency department by his friends due to bizarre behavior at a music festival. They report that he took a psychedelic drug earlier in the evening. He is experiencing intense visual hallucinations, euphoria, and paranoia, and he appears anxious and agitated. His vital signs reveal an elevated heart rate, increased blood pressure, and hyperthermia. He also reports insomnia and loss of appetite. Which of the following substances is most likely responsible for his symptoms?
