Ask Dr. Richards: 07/03

Question: I have a five-year-old female cat with extremely bad urine crystals. She chooses to urinate in an empty cat box (no litter) and if I let it evaporate for a few hours, it is caked with crystals. Should I give her medication or feed her a special diet?

Answer: Looking for the presence and evaluating the type of crystals in cat urine is a useful diagnostic tool. Finding certain rare types of crystals in a urine sample always signifies a problem. But many veterinarians believe that if the more commonly found urinary crystals are observed – at least from a cat with no past history of urinary stones and no current signs of disease – then theres little to be concerned about. Other veterinarians take a more cautious approach, believing that these seemingly normal cats are probably at higher risk of future development of urinary stones than are cats with crystal-free urine. Theyll suggest additional diagnostic tests, along with closer monitoring at home. 

Meaningful…But Only if Fresh
Urine crystals are meaningful, and only if found in fresh urine samples. But what if the veterinarian isnt able to evaluate the urine right away? How long can the sample sit around? A group of researchers recently studied the effects of storage time and temperature on crystal formation in urine samples from cats. They found that both the passage of time and the cooling of the urine after collection caused crystals to form, even in urine free of crystals when fresh from the cat. Their findings led them to recommend that veterinarians evaluate urine for crystals within an hour after collection. Any found after this period of time may be of questionable significance. 

So the crystals youve found in the drying urine in the litterbox mean very little. In fact, I would be surprised if you didnt see crystals! If left to evaporate, cat urine – any cat urine – will leave behind a crystalline deposit. Urine isnt just water; it contains many dissolved substances that will crystalize if circumstances allow. Youre able to see them simply because the urine isnt enmeshed in kitty litter. So if the crystals in the litter box are the only things that concern you about your kittys health – and if she is normal in every other way – then dont worry about it.


Question: I recently lost my pet cat, Yeti, to an acetaminophen poisoning due to a lack of communication. Yeti had many allergies, so my veterinarian told me to give her an over-the-counter antihistamine, chlorpheniramine.  His receptionist wrote, chlorpheniramine 2 mg twice a day on a post-it note, and off I went to the pharmacy. I asked the pharmacist where I could find a product containing the drug. She handed me a Tylenol product (Maximum Strength Tylenol Allergy Sinus DayTime) with exactly the right amount of the drug. It came as a gelatin tablet so it would be easier for my cat to swallow. I gave one tablet to her, but the next day she was acting weird. I called my veterinary hospital and rushed her there immediately. They tried to save her, but she died later the next evening. Please let other cat lovers know about this and how to prevent it from happening to them.

Answer: Thank you for sharing your painful experience and giving us an opportunity to warn cat lovers of the potential dangers of over-the-counter (OTC) drugs. Acetaminophen, the active ingredient in Tylenol is VERY toxic to cats. As little as 50 milligrams can poison the average-sized cat, yet each gel tab of the medicine Yeti received contains 10 times that amount.

And even though many cat owners are aware of the danger of Tylenol, its easy to forget that acetaminophen (also known as paracetamol in Britain; phenacetin is another source of acetaminophen) is often included in many other OTC medications. In fact, its the major ingredient of most aspirin-free pain relievers and cold remedies. Because cats are so very much different from humans and dogs in the way they handle medications – not even mentioning the huge difference in size – a veterinarian should always be consulted before any medication is given to a cat. And always make sure to inform the veterinarian of any other drugs present in combination products youre inquiring about giving to your cat.