The toxic effects of ibuprofen on cats include damage to the stomach and kidneys that may lead to kidney failure, severe stomach irritation and stomach ulcers, according to Vetstreet. Ibuprofen inhibits blood flow to the cat's kidneys and reduces the production of compounds that protect the inner lining of the cat's stomach.
A 200-milligram ibuprofen tablet is dangerous to a cat and causes rapid toxic effects, Vetstreet reports. Once ingested, the stomach and intestines of the animal quickly absorb the drug. Toxic effects can occur in an hour, while some signs take several days to appear, depending on the dosage of the swallowed drug. Stomach irritation is the most common side effect. In mild cases, cats experience vomiting, while they vomit blood in severe cases. Severe irritation leads to stomach ulcers and stomach perforations, which are holes in the stomach wall that enable stomach acid to flow into the abdomen. Blood transfusions are needed to save a cat that suffers from extreme stomach bleeding.
Vetstreet notes that very high doses of ibuprofen can affect the cat's brain and result in an altered mental status, seizure and coma. Veterinarians often induce vomiting to treat the toxicity when swallowing the drug is recognized immediately. Another possible treatment is sedating the cat to expel the contents of the stomach.