5-FU is a prescription drug used topically to treat skin cancer. Brand names include Adrucil, Carac, Efudex, Fluoroplex, and Tolak. 5-FU can be a life saver to humans, but fatal to cats and dogs. 

While the FDA issued a warning concerning the dangers of 5-FU to cats and dogs, many medical doctors still do not alert their patients of the dangers. 

How does a pet come in contact with 5-FU? Typically a pet will chew and puncture the tube containing 5-FU. Additionally, a pet may lick a person who has applied 5-FU to themselves. Or, a person may touch their pet after having just applied 5-FU and the pet, especially a cat, will lick off the 5-FU. Signs of toxicity can start within 30 minutes. 

If your pet is around someone who uses 5-FU, please take steps to keep them safe. Many times there is nothing your veterinarian will be able to do to help your pet after ingestion of 5-FU.

To learn more, go to “FDA Warns of Illnesses and Deaths in Pets Exposed to Prescription topical (human) cancer treatment: Fluorouracil” and “5-fluorouracil (5-FU)“.