A life-threatening drug-drug interaction between capecitabine and brivudine in a patient with metastatic breast cancer.

In the current report we present the case of a patient experiencing a life-threatening drug-drug interaction involving the concurrent administration of capecitabine and brivudine. A 65- year-old female with metastatic breast cancer was commenced on brivudine for Herpes Zoster, while on capecitabine treatment, by a physician unfamiliar with the potential repercussions of this drug-drug interaction. As a result, she developed skin rash, severe oral mucositis, and severe and prolonged pancytopenia. These side effects were attributed to a serious interaction of capecitabine with brivudine, resulting in inhibition of dihydropyrimidine dehydrogenase. The patient was admitted for supportive care including intravenous hydration, parenteral nutrition, mouth care solutions, fluconazole, antimicrobial therapy, filgrastim, red blood cell and platelet transfusions. She successfully recovered and was discharged on the 26th day after her admission. Drug-drug interactions can be serious, even life-threatening; thus the physicians should be cautious when prescribing new drugs.