Toxic to cats · Medications

Is 5-fluorouracil (5-FU) toxic to cats?

Extreme severity No safe amount — No amount is considered safe.

Yes, 5-fluorouracil (5-FU) is extremely toxic to cats. Even a small amount can be life-threatening, so treat any exposure as an emergency and contact a vet immediately. No amount is considered safe.

Symptoms to watch for

  • vomiting
  • diarrhea
  • tremors
  • seizures
  • bone marrow suppression
  • death

How vets treat it

Immediate veterinary treatment is necessary for the best patient outcome after exposure.

Why it's dangerous

The topical medication causes acute gastrointestinal distress, severe neurological impairment, and bone marrow suppression when ingested by pets.

Toxic compound: 5-fluorouracil

Good to know

Clinical signs occur within 30 minutes to 6 hours. Even a single lick can be highly toxic.

Sources

This page is informational and is not veterinary advice. If your pet has been exposed to something risky, contact your vet or an animal poison control line right away.

· How we prepare our guides

More substances toxic to cats

Acetaminophen Extreme severity Aspirin Extreme severity Calcipotriene Extreme severity Carprofen Extreme severity Everything toxic to cats →

Barcode food checks, now on iPhone.

Scan a product's barcode with StrawPaw to spot ingredients that can harm dogs and cats. The app is free to download.

Download on the App Store