title: Fluorouracil for allergic reactions to capecitabine.
abstract: OBJECTIVE
  To report the safe use of fluorouracil in a patient with breast cancer who had allergic reactions to capecitabine.
  
  
  METHODS
  A 42-year-old African American woman with metastatic breast cancer developed progressive disease. Capecitabine 1500 mg taken by mouth twice daily was prescribed as the salvage chemotherapy. She developed a generalized rash and itching, sore throat, and dizziness approximately 4 hours after the first dose of capecitabine. These reactions recurred immediately after the second dose. Capecitabine was discontinued and the allergic reactions resolved after the woman took diphenhydramine for 1 week. In view of limited therapeutic options for her progressive disease, a trial of fluorouracil 300 mg/m(2)/d continuous intravenous infusion over 5 days was initiated without any premedications. She did not experience any reactions. The dose of fluorouracil in the second cycle was increased to 400 mg/m(2)/d continuous infusion over 5 days.
  
  
  CONCLUSIONS
  Capecitabine is not intrinsically cytotoxic, but is converted to fluorouracil in tumor tissues via a 3-step enzymatic pathway. Capecitabine reaches peak blood concentrations in about 1.5 hours, with peak fluorouracil concentrations occurring at 2 hours. The elimination half-life of both drugs is 0.5-0.7 hours. The patient tolerated the rechallenge with fluorouracil without complications. Objective causality assessment revealed that the adverse event was probably drug induced. It was postulated that the allergic reaction was most likely caused by capecitabine or the intermediate metabolites based on the immediate reappearance of symptoms from the rechallenge, pharmacokinetic data, and well-tolerance of fluorouracil.
  
  
  CONCLUSIONS
  The use of fluorouracil treatment with careful monitoring can be considered in a patient with mild allergic reactions to capecitabine.
authors.affiliation: Department of Pharmacy, Harper University Hospital/Karmanos Cancer Institute, Detroit Medical Center, 3990 John R, MI 48201-2108, USA. cliu@dmc.org
authors.forename: Chin Y
authors.initials: CY
authors.lastname: Liu
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D000069287:Capecitabine; D003841:Deoxycytidine / Q000009:adverse effects* / Q000031:analogs & derivatives* / Q000276:immunology*; D004342:Drug Hypersensitivity; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D016879:Salvage Therapy / Q000009:adverse effects
chemical_list: D000970:Antineoplastic Agents; D003841:Deoxycytidine; D000069287:Capecitabine; D005472:Fluorouracil