title: [A case of phenytoin intoxication caused by interaction between phenytoin and capecitabine].
abstract: We report a case of phenytoin intoxication caused by an interaction between phenytoin and capecitabine. A 41-year-old woman was started on phenytoin (200 mg p.o. daily) for convulsive attacks due to breast cancer brain metastasis. Three months later, chemotherapy with 2,400 mg/d capecitabine (3 weeks on and 1 week off) and 1,250 mg/d lapatinib was initiated for the treatment of breast cancer. Approximately 10 weeks after starting chemotherapy, the patient began to complain of nausea, vomiting, and unsteadiness, and she was admitted to our hospital. Since her serum phenytoin level was more than 40 μg/mL, she was diagnosed with phenytoin intoxication. Phenytoin is metabolized in the liver, primarily by the CYP2C9 isozyme, which can be competitively inhibited by capecitabine. Thus, we determined that the patient developed phenytoin intoxication due to the interaction between phenytoin and capecitabine. This indicates the importance of considering the potential drug-drug interactions while prescribing anticancer agents and antiepileptic drugs simultaneously.
authors: Department of Neurology, Toyama University Hospital.
authors: Yoshiharu
authors: Y
authors: Taguchi
authors: Shutaro
authors: S
authors: Takashima
authors: Kortaro
authors: K
authors: Tanaka
mesh_terms: D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000556:secondary; D000069287:Capecitabine; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004347:Drug Interactions / Q000502:physiology*; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000031:analogs & derivatives; D006801:Humans; D008279:Magnetic Resonance Imaging; D010672:Phenytoin / Q000008:administration & dosage / Q000009:adverse effects*
chemical_list: D000927:Anticonvulsants; D000970:Antineoplastic Agents; D003841:Deoxycytidine; D010672:Phenytoin; D000069287:Capecitabine; D005472:Fluorouracil