One of the most common and effective classes of drugs for the treatment of pain are the non-steroidal anti-inflammatory drugs (NSAIDs). Like all medicines that have any benefits, they do have potential risks as well. Unfortunately, an unrealistic assessment of these risks is just as harmful as an unrealistic assessment of benefits. While many pets take these medications safely, and find relief from their pain, dramatic stories of animals who have been harmed are widely circulated, and these can generate an excessive fear in pet owners, which can lead to their denying their pets the pain relief these drugs can provide. Proponents of alternative therapies often exaggerate the risks of NSAIDs in order to frighten people into using their remedies instead, despite the fact that these are often untested and their risks and benefits not truly known.
I have previously discussed a paper reviewing the safety of NSAIDs, which concluded that while the evidence was often weak, it suggests that the risk of serious adverse effects from NSAID use is very low. This is essentially the same conclusion reached by the authors of a new, more rigorous systematic review of the literature concerning NSAIDs side effects in dogs.
Monteiro-Steagall BP, Steagall PVM, Lacelles BDX. Systematic review of nonsteroidal anti-inflammatory drug-induced adverse effects in dogs. J Vet Int Med 2013;27:1011-19.
This paper identified and critically appraised 64 studies concerning 14 different NSAIDs. The quality and quantity of the evidence was high for 3 of the drugs (carprofen, firocoxib, and meloxicam), moderate for 3 (deracoxib, robenocoxib, and ketoprofen), and low for the others drugs evaluated.
Adverse effects were reported in about ½ the studies, however aspects of the design and reporting of the studies made it impossible to determine a reliable rate of such events or the severity of them. Overall, adverse effects were reported at rates from 0% to as high as 37.5% of dogs. However, the drugs, study characteristics, and patient populations different widely, so it was not possible to directly compare particular drugs or studies.
Interestingly, when the highest quality studies were considered (randomized, placebo-controlled clinical trials), no difference in adverse effects was detected between dogs receiving NSAIDs and those on placebo. Though it is clear that such side effects do, of course, occur in some dogs on NSAIDs, and while real clinical patients are likely to respond differently than research subjects, this at least suggests that worries about common and severe harm from these medications are not justified.
A couple of interesting observations were made from these data. Adverse effects were more common in clinical trials than in research studies. This is likely associated with the fact that research subjects are usually healthy young dogs, whereas clinical trial subjects represent a variety of ages, medical conditions, and use of medications and other therapies. It is a reminder of why we cannot entirely trust research studies to predict the effects of medical treatments used in actual patients.
Gastrointestinal side effects, such as vomiting and diarrhea, were the most common in all studies, but the evidence did not allow calculation of specific rates if these symptoms. More serious side effects, involving liver and kidney problems, were only detected very rarely, and liver problems seemed only to occur in dogs with pre-existing liver abnormalities.
Overall, this study adds to the existing evidence base to suggest that NSAID side effects are uncommon, apart from gastrointestinal symptoms, and that serious injury is rare. There is unquestionably some risk associated with these medications, and the patients they are used in have to be selected and monitored carefully and appropriately. However, they are very effective pain control drugs, and denying their benefits to our pets without a realistic assessment of the risks is a disservice to our animals.