Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Pseudoscience-is-malarkey on 22/04/2016 09:29:06
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Why do veterinarians frequently prescribe dogs carprofen for pain relief, rather than simply telling their owners to give them regular analgesics that we humans use?
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Common, over-the-counter, analgesic medications for humans are frequently toxic to other animals, including dogs and cats.
The most common preparations for humans, at least in Australia, are ibuprofen, paracetamol (acetaminophen) and aspirin. Ibuprofen causes severe gastric ulceration, acute renal failure and sometimes neurological disease in dogs. In cats, it causes acute renal failure and gastric ulceration. Paracetamol causes hepatic failure in dogs, and a form of haemolytic anaemia in cats. Aspirin does it all: liver toxicity, acute kidney failure, gastrointestinal ulceration, haemolytic anaemia, neurological dysfunction, respiratory disease.
What's worse is that human medications are made in standard human-doses, for human-sized humans. These are usually MUCH higher than what should be given to a pet (even if the drug had been of a safe type in the first place). The dose rates used in humans cannot be translated directly into animal doses. Every species has different physiology, different drug absorption, drug metabolism (eg. missing enzymes for drug breakdown), and drug excretion. Drugs that cannot be metabolised or excreted will not be removed from the body, and will continue to circulate the bloodstream, causing more damage. The cells and organs of one species can be more or less sensitive to damage by a given drug, compared to another species. Adult humans are typically somewhere between 50 and 100+kg , while most pets are many times lighter than that.
Some medications are also formulated with additives such as the sweetener xylitol, which again is liver toxic in dogs.
It is unfortunately an all too frequent occurrence in both veterinary general practice and emergency medicine that pets present with life-threatening toxicities due to being given these drugs by their (often well-meaning) owners. Ironically, the toxicity is usually far worse than the condition the owner was trying to self-treat in the first place. It always sucks to die just because you had a sore toe.
Carprofen is a licensed drug for dogs in many countries, and is both widely-available and inexpensive. Being registered for administration in particular species, for a particular purpose, at a particular dose range, at a particular frequency, and by a particular route, means that that drug has been thoroughly tested in pre-clinical and clinical settings, and has been shown to be safe for use under those conditions.
A clinical exam is a good opportunity for a veterinarian to assess an animal for underlying disease, such as pre-existing liver and kidney dysfunction, so that an appropriate medication can be selected for that animal; and so that certain drugs can be avoided if there is a heightened risk for that animal's condition. The visit also allows the animal's body weight to be measured, so that the precise dose required can be calculated and prescribed. Obviously, it also allows the veterinarian assess for the actual cause of the pain and address that.
It is never a good idea to medicate an animal at home without consulting with veterinarian. Please don't.
That was the short version.
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I haven't looked at the IC50 values, but carprofen likely has a greater selectivity for canine COX2 than that of our traditional NSAID's.