Paramedics bring a middle-aged man who was found unconscious on the street to the ED. No identification orfurther information is available. Vital signs are blood pressure 160/90 mmHg, pulse rate 120 beats/minute, and respiratory rate 16 breaths/minute. Upon arrival, the patient begins experiencing sustained grand mal seizures and requires intubation. The nurse establishes an IV line. Which drug treatment is usually preferred to control status epilepticus?