Thursday 17 October 2019

Drugs can treat arthritis but beware of the risks

Pete Wedderburn

ARTHRITIS IS one of the most common diseases to affect older dogs. Some breeds are particularly prone to the problem: many readers will know older German Shepherds, Labradors and many others that suffer from the condition.

They tend to be slow to get out of their bed in the morning, and they creak around the house rather than moving quickly and nimbly. Arthritis can have a serious adverse effect on the quality of life for older dogs, and it's one of the common reasons why owners may eventually be pushed into a decision to carry out euthanasia.

Twenty years ago, there were only a few products available to treat this common disease. There are now dozens of possible treatments, ranging from pain relieving tablets and cartilage modifying injections to special diets and nutritional supplements like green lipped mussel and elk velvet antler. Physical therapies like acupuncture and hydrotherapy are also used. Many older dogs have been given extra years of goodquality life thanks to combinations of these approaches.

Unfortunately, even widely used and highly effective medications can sometimes cause dramatic adverse reactions. The headline in a British tabloid newspaper last week was typically attention-grabbing: "Could the drug that cost this beloved pet its life kill YOUR dog too?" The article told the sad story of a thirteen year old Labrador who died after taking pain-relieving medication prescribed by her vet. As a result of the article, there's no doubt that many elderly, arthritis-ridden dogs will have been rushed to their vets last week to find out if their own pets are at risk of the same fate.

So what is this drug? Why do vets prescribe medicine which may risk such a severe reaction? And when they do use this type of medication, why don't they tell owners about the potential dangers?

First, the product in question was Carprodyl, a generic form of a chemical called carprofen, which is part of a group of drugs known as non-steroidal anti-inflammatory drugs ( NSAIDS). Carprofen has become perhaps the most widely used pain relieving medication used in veterinary medicine since it was launched as "Rimadyl" by Pfizer, around fifteen years ago. The patent on the chemical has now lapsed, so a wide range of cheaper generic alternatives have become available. The drug is probably stocked in every single vet clinic in Ireland, with thousands of tablets being sold every day.

Second, why do vets prescribe it if there's even a small risk of a bad reaction? Simply put, because it's one of the most effective way of treating arthritis in dogs. Many millions of older animals have been given extra, pain-free life thanks to this type of medication. Three years ago, a major scientific review was published in the specialist veterinary press, comparing the wide range of treatments available for arthritis.

The conclusion? There was strong evidence that carprofen and two other commonly used drugs from the same group were "effective in moderating the clinical signs of osteoarthritis". There was only weak or moderate evidence that other treatments were effective. The conclusion for any vet reading this paper was clear: carprofen and other similar drugs were the most effective way of helping animals with arthritis.

Obviously, an effective drug needs to be safe, so what about those risks? While it's true that all drugs in this group can have undesirable and potentially life threatening consequences, the incidence is very low. The most common side effect is gastric irritation: affected dogs suffer from gastroenteritis which usually resolves when the medication is stopped.

Much more rarely, there's a very low risk of kidney failure associated with all nonsteroidal anti-inflammatory drugs. The cause of this is complicated: it's more common in geriatric patients suffering from underlying heart, kidney or liver disease, but it can seem to happen in a random fashion. To minimise this risk, vets often suggest blood and/or urine tests before starting a dog onto long term anti-arthritis medication. Such tests don't completely remove the small risk, and they add significantly to the cost of treatment for a pet, so they aren't always done.

So finally, why don't vets always tell owners about the potential dangers of such medication? There's a lot of variation in what happens here: some vets do take the time to tell owners about every possible side effect of every drug that's used. The problem with this approach is that many owners don't particularly want to hear a long list of potential side effects that are unlikely to happen, and they're happy to trust that the vet, on balance, feels that the medication is most appropriate having taken all the risks and benefits into account.

Vets may sometimes just mention the most common side effects ("stop the tablets and let me know if she gets an upset stomach"). Sometimes a compromise may be to hand out the package insert with the tablets: the owner can then read the full list of possible complications if they so wish (and if they have a magnifying glass).

I feel very sorry for the owners of any animal that suffers the consequences of a serious adverse reaction to medication. There's no way of removing the risk of such reactions, but not everyone wants to know about small risks. What's the best answer? If you want to be fully informed, please do ask your vet detailed questions before starting your pet onto any medication. If you're happy to listen, we're happy to tell you.

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