What can be given to a cat for a urinary tract infection?

Six year old male cat that has been fixed. All of a sudden he is growling at me and not using his litter box both which is very out of character for him.

Editors note: There are various types of urinary tract problems in cats, including stones, crystals, and cystitis. Bacterial infections are treated with antibiotics prescribed by your vet. The only way to confirm a diagnosis of a urinary tract infection is to see your vet.

Urinary blockage in male cats is life threatening and must be treated by a veterinarian immediately.

If he's growling and gone off his litter box I would suspect he's in pain and needs treatment, even if he's not blocked. I would only trust a hands on examination by a professional to know whether or not he's blocked and what his prognosis is. Please let us know what happens and how he gets on.

-Kurt