The U.S. Food and Drug Administration (FDA) has received reports of dogs and cats having serious reactions after being accidentally exposed to the topical drug 5-fluorouracil (5-FU), which is used to treat skin cancer, keratosis, and vitiligo in people. All the dogs died or were euthanized due to the severity of their condition. Cats also are especially vulnerable to poisoning by this medicine.
Pets can be exposed when they lick their owner’s skin where the topical medication is applied or by chewing on tubes of 5-FU. Nearly all cases of pets being exposed to fluorouracil are accidental. The drug is marketed under the brand names Carac, Efudex, Fluoroplex, and Tolak, and the generic name Fluorouracil Cream USP, 5%.
Signs of fluorouracil poisoning in pets usually occur within 30 minutes of exposure and include vomiting, seizures, tremors, difficulty breathing, decreased activity level, and diarrhea. Death may occur without prompt treatment. To help with awareness, the FDA has asked manufacturers to place a warning on the medicine container.
The FDA will continue to monitor reports of reactions after exposure to topical fluorouracil products and asks that reactions in pets be reported to www.fda.gov/medwatch.