Life-Threatening Reaction with Topical 5-Fluorouracil

Abstract

A 67-year-old man developed a suspected adverse drug reaction during treatment with topical 5-flu-orouracil (5-FU) for multiple actinic keratosis of the face, neck, and forearms. The man received topical 5-FU at a dosage of 0.5% for the actinic keratoses. After 1 week, he developed extreme lethargy, fatigue, fever, and mouth erosions. Several days later, and after discontinuation of 5-FU, painful mucositis and systemic side effects occurred, meeting criteria for hospitalization because of dehydration and a 6.8 kg weight loss. Hematology/oncology was consulted , and a possible systemic 5-FU reaction, similar to reactions to intravenous chemotherapy seen with a dihy-dropyrimidine dehydrogenase deficiency was suggested. The patient was not taking any concurrent medications, and he refused dihydropyrimidine dehydrogenase deficiency testing. Key Points We report a life-threatening reaction, possibly from topical 0.5% 5-fluorouracil cream, which is a lower strength dose than the only reported case of a life-threatening adverse event with 5.0% 5-fluorouracil cream. Given the common use of topical 5-fluorouracil cream, it is important for clinicians to consider the adverse side effects that can occur, especially in patients with a dihydropyrimidine dehydrogenase deficiency.