Musings about antibiotic therapy in dogs and cats

I recently attended a meeting to develop antibiotic use guidelines for dogs and cats. One recurring theme during the discussions was our paucity of scientific evidence about how to use antibiotics in certain situations. It's really interesting when you compare antibiotic treatment regimens that are used in humans and standard practices for dogs and cats. Almost invariably, we treat dogs and cats for much longer periods of time than people, even when very similar diseases are compared. Why is this?

One reason is a lack of people doing research and the difficulty performing (and funding) the large clinical trials that are needed to evaluate different treatment protocols. For example, we tend to treat urinary tract infections in dogs for 7-10 days, while in people, just 3 days of treatment is much more common. However, longer treatment courses were used in humans until various research studies showed that shorter treatment was as effective and had fewer side effects. It's likely that we could treat urinary tract infections in dogs for shorter periods of time but we don't have the data to support it at this point.

It's possible that longer treatments for certain conditions are indeed needed in dogs and cats compared to humans. An argument to this effect is that disease in pets can often be more advanced (and therefore potentially harder to treat) when first detected than similar disease in people. For example, if someone has a urinary tract infection, they are probably going to get to their physician quickly. Many owners may not notice the signs of an infection in their pets as early. More established infections may take longer to treat. Does that really happen? We don't know, but it's something we need to know to determine proper treatment durations.

"If it ain't broke, don't fix it". This isn't a very good philosophy when it comes to medicine but it's understandable. If a certain treatment plan usually works, people are hesitant to look at alternatives. The problems with longer term therapy, such as adverse effects of drugs and development of antibiotic resistance, are not necessarily considered (but they need to be).

Bottom line: We need good research to determine optimal treatment protocols for pets. It's very likely that we can greatly decrease the amount of antibiotics that we use while improving patient care, but without good evidence, it's hard to know what to do and where to start. Being too aggressive and dropping treatment times in the absence of evidence may not be a wise decision - too short a treatment period could result in treatment failures and ultimately more sick animals and overall more antibiotic use.

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Lorie Huston - January 25, 2010 11:46 PM

Interesting. Like most of us, I worry about creating antibiotic resistant "bugs" through the improper use of antibiotics, but I never really considered the comparison between humans and pets relative to the length of time an antibiotic is administered.

Your comments highlight one of the big problems in our field..trying to practice evidence-based medicine where very little research exists. It can be truly frustrating and often leads to the "best educated guess" scenario you describe here. Hopefully, with time, more research specific to animals will be forth-coming and we'll have more information available to justify (or discredit) how we treat disease.

Thank you for a very insightful post.

John Prescott - January 26, 2010 8:23 AM

Good commentary. As computerised record keeping becomes accessible, and as "chains" of veterinary practices increase, it should be straightforward to carry out large trials at the clinic level on 5 versus 10 day treatment for uncomplicated UTIs, and similar studies for other common conditions. However,experience is that it is difficult to do such trials for all sorts of reasons, which may be why we don't have this important data.
My suggested rule of thumb for uncomplicated acute bacterial infections is "clinical cure plus two days.

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