A Case of Capecitabine-induced Hyperammonemia in a Patient with Colon Cancer

Background: Hyperammonemia is an infrequent adverse drug reaction (ADR) of chemotherapy. A few cases of 5-fluorouracil (5-FU) related hyperammonemia have been reported. However, hyperammonemia induced by capecitabine, an oral prodrug of 5-FU, has not been reported till date. Case Report: A patient with colon cancer was treated with CapeOx (oxaliplatin 200mg, day 1; capecitabine 1.5g bid, days 1-14). On the fifth day of first cycle chemotherapy, she developed hyperammonemia (245 μmol/L) and psychiatric symptoms. The serum 5-FU level (3.2μg/L) was lower than normal. When the patient recovered with drug treatment, capecitabine was restarted at a lower dose (1g bid). Hyperammonemia (98μmol/L) and psychiatric symptoms reappeared after three days. Serum 5-FU remained at a low level (4.6μg/L). This case highlighted the possibility of hyperammonemia induced by capecitabine. Case reports such as these would make physicians more aware of rare ADR and what to be done in such case.