A client reports that her cat has been given Tylenol and is now unwell. What should you tell her to do?

Acetaminophen, the active ingredient in Tylenol, is highly toxic to cats, and ingestion can lead to serious health complications, including liver damage and potentially death. If a cat has been given Tylenol and is exhibiting signs of illness, it is critical to seek immediate veterinary care.

Administering acetylcysteine is a common treatment for acetaminophen toxicity because it acts as an antidote by replenishing glutathione levels in the body, which helps to detoxify the harmful metabolites produced by acetaminophen. This treatment is most effective when administered promptly after ingestion, which is why it is imperative for the client to bring her cat to the hospital as soon as possible.

Given the severity of acetaminophen toxicity in cats, merely monitoring the cat, administering more Tylenol, or just providing water without professional intervention are not appropriate responses. They do not address the underlying toxicity and could lead to further complications. Therefore, directing the client to seek immediate veterinary assistance for acetylcysteine treatment is the most responsible and necessary course of action.