Q. A 32-year-old male with newly diagnosed Hodgkin's lymphoma is admitted to the hospital for initiation of chemotherapy. He has a large mediastinal mass and extensive lymphadenopathy. During the first 24 hours after starting chemotherapy, he developed a generalized seizure. His temperature is 99.8°F (37.6°C), heart rate is 100/min, respiratory rate is 16/minute, and blood pressure is 110/70 mm of Hg. On physical examination, he looks confused and tired. Laboratory testing is shown below. Which of the following prophylactic measures would have prevented this complication?