Monday, February 7, 2011

Pet Poisons Part 8

Ibuprofen, Aspirin, and Tylenol

Ibuprofen (Advil) is a common OTC non-steroidal anti-inflammatory agent.  Because it persists in an animal's circulation longer than a human's it is significantly  more toxic to pets and should never be administered to them as a substitute for a a veterinary approved drug.  GI signs can occur at doses of 25-125 mg/kg and include vomiting, diarrhea, depression, anorexia and dark tarry stools.  These signs are due GI ulceration and bleeding and worst case scenario-catastrophic GI perforation.  The lower end of this dose is equal to 350 mg for a 30 lb dog (about 1.5 tablets) or 113 mg for a 10 dog (less than one tablet!).  Doses of 175 mg/kg are associated with renal damage (cats only 50 mg/kg is required).  This is equivalent to approximately 12 tablets in a 30 lb dog or 4 tablets in a 10 lb dog (one tablet in a cat).  Central nervous system signs including seizures and coma are seen at doses of 400 mg/kg.  If you have been doing the math you probably realized we are basing this on regular OTC strength tablets of 200 mg.  Keep in mind if you have prescription strength Ibuprofen in your home, these are 800 mg.

Treatment is aimed at preventing GI ulceration and perforation as well as renal failure.  Routine decontamination techniques are used as well as I.V. fluid therapy, and drugs such as misopristol and sucralfate which help prevent and treat ulcers.  Appropriate monitoring of bloodwork is also employed.  Prognosis is good in animals treated right away but becomes more guarded with any delay of treatment and can vary with dose. 

Aspirin (acetylsalicylic acid) toxicity often results in GI signs such as vomiting, blood in stool, and abdominal pain.  Severe intoxications can cause seizures and coma.  Renal failure is less likely to occur than with Ibuprofen toxicity but occasionally liver insult does occur.  Doses as low as 25 mg/kg in dogs can cause GI bleeding and decontamination is recommended at doses of 150 mg/kg.  Cats are more sensitive and doses of 25 mg/kg should be considered toxic.  Treatment is similar to Ibuprofen ingestions with additional therapy instituted as needed-usually in case of very extreme exposures. 

Tylenol (acetaminophen) can cause methemoglobinemia (The toxic metabolite of acetaminophen causes damage to red blood cells resulting in a product called methemoglobin. This product is problematic because it does not have the oxygen carrying capacity of regular hemoglobin.) and hepatic injury.  Because cats are deficient in a particular enzyme they are especially sensitive to the effects of Tylenol and more commonly develop methemoglobinemia whereas dogs usually develop hepatotoxicity. 

Signs include depression, difficulty breathing, increased respiratory rate, cyanosis (turning "blue") and icterus.  Facial and paw swelling are common in cats are are associated with the methemoglobinemia.  Signs of methemoglobinemia can develop within 2-6 hours while signs of hepatic dysfunction may take up to 72 hours to show.  Doses of 100 mg/kg in the dog can cause hepatotoxicity.  This is approximately 1400 mg in a 30 lb dog or 500 mg in a 10 dog.  Doses as low at 10 mg/kg can be toxic in a cat which is approximately 50 mg in an average sized cat. 

Antidotes exist for acetaminophen toxicosis and early administration along with good supportive care usually leads to recovery over 2-5 days.


Border Collie Mom said...

These seem like some fairly high doses before toxicity (at least in bigger dogs). So, are there some legitimate reasons to use these drugs? I know a lot of people that give their dogs low-dose (baby) aspirin.

Nanny McFur said...

good advice. my mom used to give her dog asprin, pepto bismal, etc. the dog is no longer with us - surprised?

Nicki said...

You should never use Ibuprofen in any pet, or Tylenol in a cat. There are some instances where aspirin is prescribed. There area some veterinarians who will also advise and owner to give aspirin at home. Personally I will not give out an aspirian dosage over the phone. Partly because of the legal ramifications (mostly these are pets I have not examined, the owner wants to save money and "treat" at home) and partly because an owner's perception of what is going on is not actually the problem. Therefore they may make it worse or just mask a disease that needs different or more aggressive therapy.

Diana said...

Ive given my dog asprin for muscle pain and the vet said it was ok. Do you think that is a mistake?

Nicki said...

If she tolerates it well and it's only occasional use then it's probably ok. If it were me though I'd use something like Rimadyl or Previcox instead.