A Case of Recurrent Hyperammonemic Encephalopathy during Adjuvant Chemotherapy(Modified FOLFOX6)for Colorectal Cancer

: A 60-year-old woman was administered mFOLFOX6 therapy as postoperative adjuvant chemotherapy for fStage III a ascending colon cancer. The patient developed a disorder of consciousness(Japan Coma Scale[JCS]III-200)immediately after the completion of the therapy. Blood ammonia levels were high at 319 mg/dL, and a diagnosis of disturbance of consciousness due to hyperammonemia was made. The patient's state of consciousness improved on the following day as blood ammonia levels decreased due to treatment with branched chain amino acid(BCAA)formulation and oxygen. Two months later, mFOLFOX6 therapy was again administered with strengthening measures for side effects to nausea and vomiting and reducing 5-FU, but the patient again developed a disorder of consciousness(JCS III-200). The 5-FU administration rate was considered as a potential cause of hyperammonemia. Hyperammonemia induced by 5-FU is relatively rare, with a reported incidence of 5-9%; however, caution is required with high dosage regimens of 5-FU that are currently recommended for colorectal cancer therapy because hyperammonemia is an important side effect.