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The Effects of Metronidazole on Dogs’ GI System

By November 5, 2020 No Comments

Raise your hand if your dog has ever been on metronidazole, otherwise known as Flagyl, to treat diarrhea 🙋🏽‍♀️. Chances are there are several hands raised as metronidazole is commonly prescribed for sudden diarrhea in dogs. If you’re thinking, so what? You may be surprised to know what antimicrobials like metronidazole can do to your dog’s digestive system.

What is Metronidazole Used For in Dogs?

Metronidazole isn’t a drug that is just randomly picked off of the shelf by your veterinarian. It is used in the treatment of diarrhea. While it won’t benefit all types of diarrhea, it may have some benefit in cases caused by protozoa, like Giardia and Trichomonas, and certain bacterial infections, such as C. perfringens. Metronidazole has also been used in conjunction with other medications to control cases of chronic diarrhea associated with inflammatory bowel disease and colitis.

In order to avoid improper use of this antimicrobial, your veterinary should perform fecal tests to determine the cause of your dog’s diarrhea to ensure that metronidazole is the treatment of choice.

What Are the Side Effects of Metronidazole in Dogs?

While metronidazole may help cure your dog’s diarrhea, it can also have some detrimental side effects that need to be taken into account. The most severe of those side effects is the toll it takes on your dog’s microbiome, that sensitive population of microbes inhabiting your dog’s gut that aid in digestion and immune function.

Antimicrobials work by killing bacteria and other microbes. They may be selective for certain classes of microbes but they often kill at least some of the beneficial bugs along with the pathogenic ones. This may not seem like a big deal, but killing off the good bacteria in a dog’s digestive system can upset how they digest and absorb nutrients and how their immune system defends their body.

This side effect is not something that we just learned of. Rather it is something that we have accepted due to the benefits that have been seen by using metronidazole. However, new research has shown that metronidazole has lasting effects on a dog’s microbiome. The most significant effect was a decrease in the population of beneficial bacteria that took at least four weeks to return to normal following completion of a dosage regime of metronidazole. This means at least four weeks that a dog’s digestion and immune function may be altered or impaired.

Other less common side effects include drooling, lethargy, bloody urine, depression, and incoordination.

What To Do If Your Dog Needs Metronidazole

The fact of the matter is that some cases of diarrhea don’t need a prescription of metronidazole and some do. If your dog falls into the ‘needs it’ category, don’t despair. There are ways that you can help your dog’s microbiome weather the Flagyl storm.

First and foremost, if your dog is experiencing any incoordination, depression, lethargy, bloody urine or anything else unusual, contact your veterinarian immediately. Drooling may nausea may be decreased by giving the medication with food. Always give the full prescribed course of antimicrobials to your pup. You don’t want to give a partial course and have the infection return full force only to need additional medications later on.

You can help boost your dog’s microbiome during and after metronidazole administration by giving probiotics and prebiotic fiber. Probiotics come in many forms but all perform the same function of helping to repopulate the gut with healthy beneficial bacteria. Yogurt is a great example of an active culture of probiotics.

Along with the probiotics, it may be beneficial to provide your pup with prebiotics. These are sources of undigestible fiber that feed the microbiome in order for it to better reproduce on its own.

It’s doubtful that the use of metronidazole for diarrhea in dogs is going to change anytime soon. It has been a go-to for Giardia and C. perfringens infections for too long. However, the realization that it alters a dog’s microbiome for a month or longer may change the way that veterinarians administer it. Performing diagnostics to better determine if metronidazole is useful is the first step. After that, providing a dog with a healthy diet and pre and probiotics will help to support that microbiome in order to keep your dog’s digestive tract happy and healthy through whatever upset they may go through.

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