http://www.fanciers.com/cat-faqs/health-care.shtml
(From Norsworthy, 1993
Medications that cats should NEVER be given:
* Acetominophen (=tylenol, paracetamol) (1 tablet can be fatal to an adult cat)
*
Benzocaine (the topical anaesthetic) (available in spray and cream forms--- Lanacaine and several hemhherrhoid preparations have lots of benzocaine)
* Benzyl alcohol
* Chlorinated hydrocarbons (like lindane, chlordane, etc.)
* Hexachlorophene (found in pHiso-Hex soap, among others)
* Methylene Blue (used to be used for urinary infections, many cats cannot tolerate it)
* Phenazopyridine (used in combination with sulfa as AzoGantrisin: fine for humans, deadly for cats)
* Phenytoin (=Dilantin) often used for seizures in other species
* Phosphate enemas (including Fleet (tm) enemas): may be fatal
http://www.petfinder.com/pet-care/pain- ... friendly=1
Pain Medication Poisonous to Cats
Charlotte Means, D.V.M., ASPCA National Animal Poison Control Center
...Local anesthetics like lidocaine, tetracaine, benzocaine or pramoxine are found in many topical antibiotic ointments and suppositories made for people. Products that contain these local anesthetics may include the phrase "plus pain relief" in the product name.
Concerned guardians often apply these topical medications to their cat's cuts or abscesses, not knowing that the local anesthetics can be absorbed through the skin or ingested during grooming. Cats are at an increased risk for toxicity because of their unique hemoglobin structure, which is easily damaged by the anesthetic. In large amounts, seizures, tremors and cardiac arrhythmia can occur. Before deciding which antibiotic ointment to keep in your cat's first aid kit, ask your veterinarian for recommendations and dosage guidelines. ...