Interaction between capecitabine and brivudin in a patient with breast cancer.

BACKGROUND: A 66-year-old woman with metastatic mammary carcinoma, who was being treated with capecitabine, contracted a herpes zoster infection that was treated with the antiviral drug brivudin. A drug-drug interaction between brivudin and capecitabine caused medullar aplasia, serious toxic effects to the intestinal mucous membrane, hand-foot syndrome, onycholysis and dental pigmentation. INVESTIGATIONS: Physical examination, blood analysis, blood cultures, chest X-ray, bone marrow aspiration and biopsy. DIAGNOSIS: Serious adverse event secondary to inhibition of dihydropyrimidine dehydrogenase by a drug-drug interaction between capecitabine and brivudin. MANAGEMENT: Intravenous hydration, imipenem, red blood cell and platelet transfusions, filgrastim, omeprazole, care of the mouth and feet, topical anesthetics, systemic analgesics and parenteral nutrition.