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Dear Daisy Dog

I use Efudex cream for my skin problem, solar keratoses. When I apply it to my face, Winston, my Labrador retriever, tries to lick it off. Is it safe for him?

Daisy Responds

No. Efudex is toxic when pets ingest it.

Besides, it needs to remain on your skin to prevent your solar keratoses from developing into squamous cell carcinoma.

Efudex contains fluorouracil (“floor-oh-your-a-sill”), a powerful anti-cancer drug humans use to treat skin disorders associated with excessive ultraviolet light exposure. These include solar (or actinic) keratoses and basal cell carcinoma.

Other skin products that contain fluorouracil are Fluoroplex and Carac.

Unfortunately, fluorouracil ranks near the top of the Animal Poison Control Center’s list of human drugs that commonly poison pets.

When ingested, the drug can cause severe vomiting, uncontrollable seizures and even death.

Other possible effects are lethargy, bloody diarrhea, tremors, cardiac arrhythmia, respiratory depression and decreased white blood cell count.

Dogs most often are poisoned when they chew on their humans’ fluorouracil tubes or dropper bottles and consume the drug.

Toxicity develops at just 4 mg per pound of dog, and death occurs at 9 to 14 mg per pound – less than half a tube for a dog Winston’s size.

Clinical signs begin 30 minutes to five hours after ingestion. Despite aggressive treatment, most affected dogs die.

Tragically, physicians and pharmacists rarely warn people about the risks fluorouracil poses to their pets, and most people assume skin creams are innocuous.

To protect Winston, don’t let him lick your face, and don’t leave your Efudex tube on a counter or table, where he can snatch it. Always store it securely in a drawer or medicine cabinet.

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