Question

A 20-year-old male university student is brought to the emergency department by his roommate due to severe agitation and confusion. The roommate reports that the patient has been acting increasingly bizarre over the last six hours. When questioned, the roommate admits the patient ingested multiple bottles of over-the-counter dextromethorphan-containing cough syrup earlier today in an attempt to experience hallucinations. The patient has a history of major depressive disorder, for which he takes daily fluoxetine. Vital signs show a temperature of $39.4^\circ\text{C}$ ($102.9^\circ\text{F}$), pulse of $134/\text{min}$, blood pressure of $172/105\text{ mmHg}$, and respiratory rate of $22/\text{min}$. Physical examination reveals a diaphoretic, flushed young man who is disoriented to time and place. He exhibits spontaneous muscle twitching and a coarse bilateral tremor. Neurologic examination is notable for marked hyperreflexia in the lower extremities and sustained ocular clonus. In addition to providing intravenous fluids and supportive care, which of the following is the most appropriate next step in management?