For years, I've been telling members here not to allow their dogs to be given metronidazole without a really good reason. Here is another article which cites studies backing up what I've been saying, that metronidazole is ineffective for treating giardia, ineffective for many types of diarrhea, and causes a persistent bacterial imbalance in the gut which leads to further digestive issues. Here's one more article which cites studies backing up what I've been telling you guys for years..
From the article:
"If your dog has diarrhea, a course of metronidazole (also known by the brand name Flagyl) might be the appropriate treatment. But for many veterinarians, this antibiotic has become a knee-jerk response to dog diarrhea based on historical practice and theories rather than scientific evidence. A growing body of research suggests that metronidazole is much less effective for some gastrointestinal conditions than was previously thought. And now we know that in addition to troubling side effects, metronidazole can cause unhealthy long-term changes in your dog’s gut microbiome.
Because metronidazole works well for certain conditions that cause diarrhea (such as C. diff), it’s become the most frequently used antibiotic for dog diarrhea in general. But in too many of these cases, metronidazole may be the wrong choice. Several studies have found, for instance, that metronidazole doesn’t actually help inflammatory bowel disease (IBD) or acute diarrhea in dogs.
In the past, metronidazole worked well against Giardia, a protozoan parasite that causes diarrhea in dogs. Over time, however, that organism has developed a resistance to metronidazole, so this medication is no longer effective by itself against Giardia.
Along with the troublemaking bacteria they’re intended to target, most antibiotics also kill off a lot of the “good” bacteria the body needs for healthy functions like digestion. As a result, important members of the gut microbiome can go missing, leading to unhealthy bacterial imbalances. A new study published this year in the Journal of Veterinary Internal Medicine has called attention to the dramatic effects of metronidazole in particular on the gut microbiomes of dogs.
The authors found that in healthy dogs, a 14-day course of treatment with metronidazole resulted in significant changes in the composition of the gut microbiome, including decreases in important beneficial bacteria, such as Fusobacteria—one of the dominant groups of bacteria in the gut microbiomes of dogs (and cats)—and reductions in overall richness (the number of different bacterial species present). And these effects weren’t just temporary: four weeks after the dogs had stopped receiving metronidazole, these microbiome changes still had not fully resolved, meaning that these dogs still didn’t have enough of some of the bacteria necessary for healthy gut function.
The study’s authors recommend that veterinarians adopt a more cautious approach when using metronidazole in dogs, especially dogs that may already have imbalanced gut microbiomes."
Please remember this when your vet recommends metronidazole. :)