Metallic Taste as a Side Effect of Topical Fluorouracil Use

October 2011 | Volume 10 | Issue 10 | Case Reports | 1201 | Copyright © October 2011

as a potential gastrointestinal side effect of the medication,13 to our knowledge, this is the first report of metallic taste associated with topical use of topical 5-fluorouracil in the literature.
Systemic administration of 5-fluorouracil, however, has been implicated in the development of dysgeusia in 2-7 percent of patients receiving this medication.14,15 Altered taste sensation is a commonly reported problem among cancer patients receiving systemic chemotherapy, with up to 75 percent of chemotherapy patients reporting such changes.16,17 The mechanism behind these disturbances is not well understood but is thought to involve damage to cells responsible for taste. The medication may destroy taste receptor cells within taste buds.18 These cells have a high turnover rate of 10 days and are susceptible to toxicity from chemotherapeutic agents.19 These medications may also affect neuronal cells leading to disruption of afferent taste pathways.18
Initial studies in absorption of radiolabeled, topical 5% 5-fluorouracil showed that ~6 percent of the topical dose is systemically absorbed.20 Other studies showed absorption to be only 2.6 percent, but diseased skin had 15-75 times greater absorption compared to healthy skin.21,22 While our patient only applied 5-fluorouracil to a limited body surface area, systemic absorption of the medication likely accounts for her transient dysgeusia. Other common side effects of systemic 5-fluorouracil include myelosuppresion, mucositis and diarrhea. Life-threatening toxicity due to topical application of 5-fluorouracil for treatment of basal cell carcinoma has been reported.23 In that case, the patient was found to have a deficiency of dihydropyrimidine dehydrogenase (DHD), the initial rate-limiting enzyme in the metabolism of fluorouracil, which led to severe hematological and gastrointestinal toxicity. While the DHD status of our patient is unknown, we do not recommend use of fluorouracil over any larger surface area in this patient in the future due to the potential for more serious side effects.
Dysgeusia, which developed during topical fluorouracil treatment for squamous cell carcinoma in situ, was fortunately a self-limited side effect in our patient. Given that this medication is frequently applied over larger body surface areas than in our patient, those prescribing this medication should be aware of rare but potentially serious side effects of this medication due to its systemic absorption.


The authors have no relevant conflicts of interest to disclose.


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