Dear Dr. Jody: Occasionally, our 8 year old lab, “Sadie”, seems stiff and sore after a good day’s exercise. We don’t want her on long term pain medication, but we would like to be able to relieve her discomfort as needed. Are there safe, low doses of Advil or Tylenol that we can give her from time to time?
Thank you for asking! I am always so relieved when owners take the time to ask this question before medicating their pets at home. It is surprising how frequently a pet owner will mention to me that they have given their pet a human pain reliever. Although most pet owners give relatively low doses (often using baby aspirin or Advil), this is still a potentially life-threatening practice.
It is important to understand that dogs and cats are not little people in fur suits. Dogs and cats are vastly different physiologically from people. When a human takes Tylenol (acetaminophen), a variety of complex chemical reactions occur in the liver to break the drug down into non-toxic components that are harmlessly excreted by the kidneys and into the urine. One of the enzymes that catalyze these chemical reactions is called glucuronyl transferase, or GT. Cats do not possess GT in their bodies. Because felines lack this critical enzyme, even a minuscule dose of Tylenol is rapidly fatal to an otherwise healthy cat. Tylenol can, in rare instances, be safely used in dogs; however, not only must the dose be carefully calculated by a veterinarian, but the dog’s bloodwork requires frequent evaluation to ensure that no long term damage is occurring.
Advil (ibuprofen) is another pain reliever that I see used non-judiciously by pet owners. Allow me to explain how this non-steroidal anti-inflammatory (NSAID) works.
NSAIDs such as ibuprofen work by inhibiting the production of prostaglandins. Prostaglandins chemicals that are involved in the development of inflammation and the perception of pain. By inhibiting the production of prostaglandins, NSAIDs are decreasing inflammation and the perception of pain. Sounds pretty good, doesn’t it?
Well, yes and no. Prostaglandins also have some other important functions. One of these important actions is that they promote the secretion of the protective mucus lining in the stomach. Without this lining, highly acidic and corrosive stomach juices can easily start to digest the lining of the stomach, leading to stomach ulcers. When prostaglandin production is inhibited by NSAIDs, the protective mucus barrier disappears. Dogs and cats are more sensitive to this process than humans, and are far more likely to suffer from ulcers as a result of NSAID use, even at very low doses.
Prostaglandins also promote a healthy blood supply to the kidneys. When prostaglandin production is inhibited, renal blood flow is compromised and kidney failure can easily develop within a few days of ibuprofen administration.
A third human pain reliever that clients frequently administer to their pets is aspirin (acetylsalicylic acid or ASA). One of the prostaglandins that ASA inhibits is the prostaglandin that makes platelets sticky. Platelets are the tiny little structures floating around in your bloodstream that allow you to clot your blood when you are injured. In order for platelets to form a clot, they must be able to adhere together once the clotting reaction has been initiated. The administration of ASA inhibits the production of the particular prostaglandin that makes platelets work properly. This is the reason that low doses of aspirin are used as a “blood thinner” or anti-coagulant in human patients who are at risk of forming blood clots that may lead to certain heart diseases or stroke. The good news for humans taking this medication is that our bodies metabolize and eliminate the drug fairly rapidly and it does not build up in our system. When a person takes a single dose of aspirin, all traces of the drug have been eliminated from the body within 30 hours, which makes daily dosing reasonable.
When a dog takes a single dose of aspirin, detectable levels of the drug persist for three days. This means that, if you give your dog one dose of aspirin daily, you are giving each subsequent dose when there are still significant quantities of aspirin in his body from the previous day’s dose. Over the long term, this can dangerously inhibit your dog’s ability to clot his blood. And what about cats? A single dose of aspirin remains in your cat’s body for three weeks! That is, if your cat survives the other potential side effects of gastric ulceration and kidney failure that might result from the use of human NSAIDs in a species for which they are not designed.
There have certainly been occasions when I have prescribed ASA for dogs. But these doses are very carefully calculated and are used for very short term treatments for very specific ailments.
The good news is that researchers have developed NSAIDs specifically for cats and dogs. These medications are far less likely to cause the inhibition of the helpful prostaglandins than human NSAIDs, and are therefore highly unlikely to lead to kidney disease, stomach ulcers, or clotting problems. Because of the unique physiology of cats, fewer options exist for owners of cats who require long term pain medication, but there are still a few choices available. Please consult your veterinarian if you would like safe pain relief options for your pet.
Remember – just as you would not take your pet’s pain medication, you should not offer your own pain medication to your pet!
-- Dr. Jody McMurray, D.V.M., B.Sc.
Heartland Veterinary Clinic
Bay 300 - 2700 Main Street South
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