[A case of 5-fluorouracil-induced hyperammmonia after chemotherapy for metastatic colon cancer].

A 79-year-old woman with colon cancer and multiple liver metastases was admitted to our hospital for systemic chemotherapy. She underwent first cycle of modified FOLFOX6 chemotherapy. She was confused on treatment day 5. Blood test revealed her serum ammonia level to be 121 microg/dl. We diagnosed 5-fluorouracil (5FU)-induced hyperammonemia. Conservative treatment resulted in improvement of metal status. The reason for hyperammonemia after administration of 5FU was the excess production of ammonium from metabolites of 5FU.