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. 2023 Jul;14(5):414-418.
doi: 10.6004/jadpro.2023.14.5.6. Epub 2023 Jul 1.

Hyperammonemia Secondary to 5-Fluorouracil

Affiliations

Hyperammonemia Secondary to 5-Fluorouracil

Ashley Scott et al. J Adv Pract Oncol. 2023 Jul.

Abstract

5-fluorouracil (5-FU) is one of the most common adjuvant antineoplastic agents used in the treatment of localized and metastatic colon cancer. Frequent side effects of 5-FU include myelosuppression, mucositis, nausea, vomiting, and diarrhea. However, hyperammonemic encephalopathy is a rare neurologic toxicity that can occur after 5-FU chemotherapy administration. Patients with 5-FU-induced hyperammonemic encephalopathy often exhibit symptoms of altered mental status with no radiologic abnormalities or laboratory abnormalities except for significantly elevated ammonia levels with occasional lactic acidosis and respiratory alkalosis. We report a case of a patient with stage IV colon adenocarcinoma who experienced altered state of consciousness due to hyperammonemia during the administration of palliative chemotherapy with 5-FU, bevacizumab, and leucovorin. On cycle 1 day 2 of chemotherapy, the patient became drowsy and confused at home, prompting a visit to the emergency department and ultimately hospital admission. Laboratory tests revealed an elevated blood ammonia level (838 μg/dL). After an extensive negative workup, his altered state of consciousness was thought to be secondary to 5-FU-induced hyperammonemia. Upon admission, 5-FU was immediately discontinued and the patient was treated with lactulose enemas, intravenous fluids, rifaximin, and continuous renal replacement therapy with gradual recovery to baseline mental status. It is crucial for advanced practitioners to be aware of this rare side effect to ensure prompt diagnosis and maximize treatment effectiveness.

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Conflict of interest statement

The author has no conflicts of interest to disclose.

Figures

Figure 1
Figure 1
Ammonia level trends during day 1 of hospitalization through day 5 of hospitalization when ammonia level normalized. The following are the ammonia values respectively: 838 μg/dL (day 1),1,704 μg/dL (day 2 AM), 1,649 μg/dL (day 2 PM), 237 μg/dL (day 3), 15 μg/dL (day 4), < 15 μg/dL (day 5).

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