The FDA published a consumer update on September 7, 2022 regarding the potential harm faced by pets that come into contact with the topical skin cancer cream fluorouracil, also knowns as “5-FU” or “5-fluorouracil.” Containers of the topical cream or solution may include the brand names Efudex, Carac, Tolak, or Fluoroplex.

Fluorouracil, if ingested, can be deadly to pets. FDA has received reports involving dogs that were exposed to the drug and all of the dogs died. If your prescription list contains fluorouracil, immediately move the drug somewhere out of reach of your pets and keep them from licking your skin where you’ve applied the medicine. FDA has not received any reports of fluorouracil poisoning in cats or other pets but recommends the drug be kept away from all pets.

Fluorouracil is an FDA-approved chemotherapy drug commonly used to treat a wide variety of cancers in people, including some types of skin cancers and a condition called solar or actinic keratosis, which can lead to skin cancer. It’s also used to treat warts in children and occasionally in veterinary medicine to treat cancers in horses. Pets can be exposed to fluorouracil by chewing on containers, usually tubes, of topical fluorouracil or by licking the area of your skin where you applied the medicine.

Signs of fluorouracil poisoning in pets can start within 30 minutes, and include vomiting, shaking, seizures, difficulty breathing and diarrhea. Death can happen in as little as 6 to 12 hours after a pet is exposed to fluorouracil. If your pet comes into contact with fluorouracil, seek immediate veterinary care, and bring the container of fluorouracil with you.

Because so many pet owners and healthcare providers are unaware  of how deadly fluorouracil is to animals, the FDA asked makers of fluorouracil topical products to add new wording to the product labels that warn users about the danger to pets. For example, the new wording states, “May be fatal if your pet licks or ingests. Avoid allowing pets to contact this tube or your skin where fluorouracil has been applied. Store and dispose out of reach of pets.”

If your pet has a problem with fluorouracil or any other human or animal drug, please report it to FDA’s Center for Veterinary Medicine. In the meantime, keep all drugs for people and animals stored safely and out of reach of your pet. Safely storing your fluorouracil topical products can save your pet’s life.

Click here to read the full FDA consumer update on fluorouracil, including tips on how to keep pets safe when this drug is in your home.