Efudex (Fluorouracil) Toxicity in Dogs

Other common brand names include Adrucil, Fluoroplex, 5-FU and Carac. Once a canine ingests Efudex it is quickly absorbed from the gastrointestinal tract. Symptoms of the toxicity can be observed within 30 to 45 minutes. Toxicity usually manifests itself mainly in the gastrointestinal, respiratory or neurologic systems. 

If your pet has ingested any amount of Efudex, get him to a veterinarian or veterinary emergency clinic immediately.  It is a good idea to call them beforehand to let them know you are coming in with a dog that has ingested Fluorouracil.  You can also call the ASPCA Animal Poison Control Center (APCC) for guidance.

Efudex (Fluorouracil) is a common prescription anti-cancer medication used topically for humans. Efudex (Fluorouracil) is extremely poisonous if ingested by a dog, even a small amount can be fatally toxic.

Common symptoms may be:

• Tremors
• Drooling
• Vomiting with or without blood
• Seizures
• Diarrhea with or without blood
• Bone marrow suppression
• Poor appetite 
• Weakness
• Dehydration
• Ataxia

Efudex is very dangerous to pets; it is extremely toxic to rapidly dividing cells and can cause severe gastrointestinal symptoms.  Toxic doses can be as little as 5 mg/kg, and doses ≥40 mg/kg are reported to be fatal. Unfortunately, pharmacists and physicians do not always warn of the potential toxicity some medicines may pose to pets.

• Ingesting a tube of Efudex (Fluorouracil) cream 
• Licking the skin of someone that has used Efudex
• A pet owner may apply cream on the skin and then handle the pet;  the dog then grooms his fur, ingesting Efudex

Your veterinarian will take a medical history of your pet, which will include if he is currently on any medications. It is critical that you let your veterinarian know how much Efudex (Fluorouracil) your pet has ingested and the approximate the time that it happened.

Your veterinarian will run blood tests to check your pet’s electrolyte levels and blood cell counts. When a dog ingests Efudex (Fluorouracil) he will often have low white cell counts, abnormal electrolyte concentrations, and dehydration.

Efudex toxicity must be treated immediately and aggressively. If your pet has been brought into the veterinarian within an hour of ingesting Fluorouracil, your veterinarian will induce emesis and will administer activated charcoal and a cathartic. The veterinarian team will have started an IV to keep your pet hydrated.  

To help protect your canine’s gastrointestinal tract, sucralfate and gastric acid inhibitors may be given to your pet. Dogs that are having seizures will be given diazepam, and often pentobarbital or phenobarbital may need to be added. The white cells known as neutrophils are vital in fighting infections; if they become too low, administration of filgrastim or granulocyte may be useful. Pain medications will also be administer to your pet.

Your pet will be need to be hospitalized for a period of time to help keep him stable.  Blood work will be repeated to determine if there is ongoing organ damage and to see how well your pet is responding to the treatment.  Your pet’s body temperature, electrolytes and serum chemistries for liver and renal failure will need to be monitored closely.

Prognosis is not always good because of the rapid absorption of Efudex (Fluorouracil) in the canine’s body. Death often occurs due to secondary complications such as bacterial infection of the blood (sepsis), brain hemorrhage and or gastrointestinal tract bleeding.

When the veterinarian team releases your pet, it is important to follow their treatment plan.  Your dog may need to eat a bland diet for a short amount of time.  Follow-up visits will be necessary to retake blood work and check on his progress.  If your pet experienced bone marrow suppression or pulmonary complications he may have long-lasting effects, your veterinarian will discuss a treatment plan with you. 

Efudex is also toxic to cats.  Most cats will die from a very small exposure to Efudex , canines have a slightly better prognosis with 25% survival. Some precautions to help keep pets safe from medications:

• It is important to keep medications out of the reach of our pets, inside a cabinet is the best choice as pets can jump and reach medications left on a counter
• It is critical that you wash your hands thoroughly after applying any ointment before handling your pet or his food bowls
• Do not let your pet lick your skin if there has been a recent application of ointment or cream medication
• Let family and friends know about the potential dangers of human medications