1.  CNS lymphoma.  Upon admission, she was started on her Rituxan, which she tolerated well.  She was then hydrated with bicarbonate solution to a urine pH of 8.  She received methotrexate 5 g/m2.  24-hour creatinine was 0.9, 48-hour methotrexate level was elevated at 2.08.  This was likely secondary to the need to initiate treatment with antibiotics secondary to infection.  Her leucovorin was increased to 100 mg/m2.  72-hour methotrexate level was 0.58.  96-hour methotrexate was 0.16, and 19-hour was 0.08.  She continued additional four doses of oral leucovorin.  Her creatinine improved.  On day prior to discharge, she received her weekly dose of Rituxan.  She will return for Rituxan next week and then return for an appointment with Dr. X on August 18, 2008 with plans for admission for next cycle of methotrexate.