Has your dog been prescribed metronidazole? Here’s why it might not be the best course of treatment.

Veterinarians often prescribe the antibiotic metronidazole (Flagyl) to treat the many causes of acute diarrhea, but a growing body of research suggests that it is much less effective for some gastrointestinal conditions than previously thought and comes with some troubling side effects. Below we provide important information about metronidazole to help you advocate for the long term health of your dog.

Metronidazole and the gut microbiome

Metronidazole, like all other antibiotics, targets bacteria. Unfortunately this includes killing off both the ‘bad’ bacteria that cause infection and the ‘good’ bacteria that are needed for healthy bodily functions.

A recent study published in the Journal of Veterinary Medicine found that a 14-day course of metronidazole resulted in significant changes to the bacteria in the digestive tract of dogs, including a decrease in important beneficial bacteria known to be key players in healthy gut function. The effects weren’t just temporary either: the gut microbes still had not fully recovered even four weeks after the end of treatment.

This finding doesn’t mean that dogs shouldn’t be given metronidazole or other antibiotics; it means that veterinarians and dog parents should make sure that the choice to use metronidazole is the best treatment option.

How to talk to your veterinarian about metronidazole treatment

Start by asking your veterinarian if your dog even needs antibiotics. In fact, research from the last decade has shown that metronidazole treatment is no different than placebo controls in treating acute diarrhea (diarrhea that lasts only a few days). In many cases of dog diarrhea, symptoms can resolve with just supportive care and antibiotics can even make diarrhea worse.

Ask your veterinarian about when Metronidazole is the right choice. For instance, if your dog has inflammatory bowel disease (IBD), metronidazole is not the best choice because it is particularly disruptive to gut bacteria. However, if your dog’s digestive issues are caused by a Clostridium difficile or Helicobacter pylori infection, then metronidazole may be the best treatment option.

If your dog needs antibiotics, make sure to discuss additional supplements that you can use to support your dog during treatment. For example, certain probiotics (such as Saccharomyces boulardii) and prebiotics (such as inulin) can help reduce antibiotic side effects and improve recovery time. Dog parents can also test their dog’s gut microbiome following antibiotic treatment to determine if a bacterial imbalance is present.

Prescribed metronidazole for Giardia?

Metronidazole is still widely prescribed for dogs with Giardia even though the protozoan parasite has developed a global resistance to it. The medication is no longer a sufficient treatment by itself. This is the case for many antimicrobials: the development of antimicrobial resistance has caused a decrease in global effectiveness of antibiotics and makes it harder to treat infections.

While metronidazole and other antibiotics can be valuable tools in treating a sick dog, it’s important to make sure the chosen drug’s effectiveness in a given situation is supported by current scientific evidence. We encourage you to talk with your veterinarian about these issues to advocate for the long term health and happiness of your dog.