A 52-year-old woman is brought to the emergency department after being found walking in the middle of a freeway on-ramp. She was given intramuscular haloperidol by emergency medical personnel for agitation on the way to the hospital. Her medical history is notable for polysubstance use.
On physical examination in the emergency department, she is alert and restless but calms down with verbal reassurance. Blood pressure is 155/90 mm Hg, and pulse rate is 110/min. She is admitted to the observation unit.
One hour later, she becomes severely agitated and tries to leave. Temperature is 38.2 °C (100.8 °F), blood pressure is 210/104 mm Hg, pulse rate is 124/min, and respiration rate is 14/min. Oxygen saturation is 97% breathing ambient air. The pupils are symmetric, dilated, and reactive to light. Slight tremor of the hands is noted. No tongue fasciculations are observed. The skin is warm and diaphoretic. The chest is clear to auscultation.
Laboratory studies reveal a serum creatine kinase level of 6600 U/L, creatinine level of 1.1 mg/dL (97.2 µmol/L), and a normal troponin level.
An electrocardiogram reveals sinus tachycardia without ischemic changes.
Which of the following is the most appropriate next step in treatment?