Key takeaways:
Metronidazole (Ayradia, Flagyl) is a popular antibiotic that a veterinarian may prescribe for a dog to treat diarrhea, inflammatory bowel disease, or infections.
The most common side effect of metronidazole is diarrhea, even though it can be prescribed to treat diarrhea.
Metronidazole has long-term risks and can cause serious side effects in dogs, including tremors and seizures.
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Antibiotics can be valuable options to treat your sick dog. If an infection is causing your dog to have diarrhea, your veterinarian may recommend the antibiotic metronidazole (Ayradia, Flagyl). Metronidazole is a commonly prescribed antibiotic for dogs with diarrhea and other gastrointestinal problems.
Let’s take a closer look at what metronidazole can treat, common side effects, and how you can best treat your dog’s diarrhea.
Metronidazole for dogs at a glance
Common name | Metronidazole (Ayradia, Flagyl) |
What it treats | Infections, diarrhea, inflammatory bowel disease (IBD) |
How it comes (forms) | Tablet, capsule, oral liquid |
Dosage | Depends on a dog’s weight and the type of infection |
Common side effect | Diarrhea, loss of appetite, upset stomach |
Average cost |
What is metronidazole for dogs, and how does it work?
Metronidazole is a prescription antibiotic used to treat many types of infections in dogs. It works by stopping bacteria or parasites from growing and multiplying. Metronidazole can also reach the central nervous system and bones. This makes it helpful for brain, spinal cord, and bone infections.
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What is metronidazole used for in dogs?
Metronidazole is commonly prescribed for dogs to treat infections and inflammatory conditions that cause diarrhea. It is also sometimes used to treat inflammatory bowel disease (IBD). Veterinarians often use metronidazole as an off-label medication since it is not FDA-approved for dogs.
There is one FDA-approved version of metronidazole for dogs. It’s an oral liquid sold under the brand name Ayradia. It’s FDA-approved to treat infections caused by Giardia duodenalis parasites.
How is metronidazole given to dogs, and what is the standard dosage?
Metronidazole is available for dogs as a tablet or capsule you give by mouth. Because it can have a bitter flavor, you may want to disguise the medication with peanut butter or another favorite treat of choice. Metronidazole is also available as an oral liquid you can give instead of pills. The liquid form can be helpful if your dog has issues swallowing pills.
Metronidazole should be fully absorbed by your dog’s body within 1 to 2 hours. But it may take a few days for your dog’s symptoms to improve. Even if they’re feeling better, be sure your dog finishes all the pills prescribed unless your vet tells you otherwise. This will help ensure the infection is gone.
What is the dosage of metronidazole for dogs?
The dosage of metronidazole is based on how much your dog weighs and what’s causing their infection. Their dosage may start at 7.5 mg to 10 mg per kilogram of body weight. But this really depends on their infection. Your dog may need a higher or lower dose.
Your veterinarian will determine the best dosage depending on how well your dog responds to the medication and if they develop side effects. Most times, your dog will take the medication twice a day for 5 to 7 days.
Avoiding accidents: While diarrhea is relatively common in dogs, there are steps that you can take to help prevent it. Learn how to avoid common triggers and a few at-home remedies that can help you manage it.
How to give medication to your dog: Getting your pet to take even the most cleverly disguised medication can be challenging. To help your dog take a pill or liquid medication, try these vet-approved strategies.
Other antibiotic options: Metronidazole is commonly prescribed for digestion issues in pets. Learn about other antibiotics prescribed for dogs with bacterial and parasitic infections.
What should you do if your dog misses a dose of metronidazole?
If you miss giving your dog a dose of metronidazole, give them the dose as soon as you remember. If it’s close to when they’re supposed to get the next dose, though, skip the missed dose. Then give the medication at the regularly scheduled time. If you’re unsure what to do, call your veterinarian and ask for guidance.
What are the side effects of metronidazole in dogs?
Metronidazole can lower the amount of healthy gut bacteria in dogs, which may cause more diarrhea in dogs. Its bitter flavor may also cause more drooling than usual.
Other common side effects of metronidazole are:
Upset stomach
Gagging
Feeling more tired than usual
Discolored urine
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What are the most serious risks of metronidazole for dogs?
All medications can have serious risks for dogs, including metronidazole. These risks can include:
Wobbly gait (ataxia)
Rapid eye movements
Tremors
Weakness
Serious side effects are rare. These problems are more likely to happen if your dog is taking this medication at high doses or for a long time. If you notice any of these symptoms in your dog while they’re taking metronidazole, call their vet or visit an animal hospital right away.
Which dogs shouldn’t take metronidazole?
Metronidazole is not safe for pregnant dogs because it can cause birth defects. This medication is also not safe for nursing dogs because it passes into breast milk and can be harmful to young puppies. Lastly, it is not the best option to give metronidazole to dogs with seizures or kidney or liver problems.
Are there any interactions between metronidazole and other medications?
Yes. Several other dog medications can interact with metronidazole.
Metronidazole can interact with the blood thinner warfarin (Coumadin) and raise the risk of bleeding. If your dog is taking both medications, the vet may temporarily lower their warfarin dose before starting them on metronidazole. Your pet may also need closer monitoring while taking this combination.
Cimetidine, a heartburn remedy, can also interact with metronidazole. Metronidazole will have a stronger effect when taken with cimetidine. So your dog is more likely to experience antibiotic-related side effects if they take this combination.
Seizure medications, such as phenobarbital and phenytoin (Dilantin), can stop metronidazole from working as well. If your dog takes these medications, your veterinarian will most likely choose a different antibiotic for them.
Dogs taking cyclosporine and metronidazole together may experience more side effects from the cyclosporine (Atopica).
It’s important to note that these are not the only interactions for metronidazole — just some of the most notable. Provide your vet a complete list of all medications and supplements your dog takes before starting them on metronidazole. This helps ensure that your pet can safely take their combined medications.
Are there any alternatives to metronidazole for dogs with diarrhea?
Yes. Alternative treatments are available, depending on what’s causing your dog’s diarrhea. Besides infections, other possible causes of diarrhea in dogs include IBD, tumors, and pancreas problems. Diarrhea can sometimes also be a side effect caused by other antibiotics.
Other medications that might be used to treat diarrhea in dogs include:
Fenbendazole (Panacur C) for Giardia infections
Tylosin (Tylan) for IBD
Sulfasalazine (Azulfidine) for IBD
Keep in mind that most acute diarrhea — meaning it’s not caused by a chronic condition — should resolve within a week whether your dog takes medication for it or not. If you see blood in your dog’s poop at any point, contact your veterinarian right away. If your dog still has diarrhea after 7 days and hasn’t been taking medication, consult your veterinarian.
Are medications always necessary to treat diarrhea in dogs?
No. Supportive care is sometimes tried before medications. For example, during the first 12 to 24 hours of your dog’s diarrhea, your vet may recommend withholding food or providing small meals every few hours.
Other supportive care that may help with diarrhea in dogs includes:
Changing their diet
Feeding them more fiber
Giving them probiotics
Dietary changes may include adding fiber or trying hypoallergenic dog food if your vet feels your dog might have a food allergy. Canned pumpkin is an excellent source of fiber you can add to your dog’s meal. Your vet may also recommend adding fiber with Metamucil or coarse wheat bran.
You may be instructed to try these dietary suggestions for your dog, along with antibiotics such as metronidazole. Regardless of whether you are providing your dog medications, supportive care, or both, follow your vet’s recommendations. This will ensure your furry friend gets back to feeling like themselves as quickly as possible.
Frequently asked questions
The side effects of metronidazole in dogs usually last until the medication is out of their system. Metronidazole should be completely out of your dog’s system about 20 hours after stopping the medication. Ask your veterinarian what to expect if you’re concerned about your dog’s side effects while they’re taking metronidazole.
The best way to mask the taste of metronidazole for dogs is to give the medication in a treat. The medication has a bitter taste, so pick your pup’s favorite, flavorful treats.
The side effects of metronidazole in dogs usually last until the medication is out of their system. Metronidazole should be completely out of your dog’s system about 20 hours after stopping the medication. Ask your veterinarian what to expect if you’re concerned about your dog’s side effects while they’re taking metronidazole.
The best way to mask the taste of metronidazole for dogs is to give the medication in a treat. The medication has a bitter taste, so pick your pup’s favorite, flavorful treats.
The bottom line
In many cases of diarrhea, your dog may not need an antibiotic. If they do, the antibiotic metronidazole (Ayradia, Flagyl) might be what your veterinarian prescribes. Metronidazole is available for dogs in pill form or as an oral liquid. Common side effects include diarrhea, an upset stomach, and loss of appetite.
Be sure your pet finishes all the metronidazole that was prescribed. This will help clear their infection and prevent it from returning. Most important, follow your vet’s advice and recommendations about how to best manage your dog’s diarrhea. Be sure to follow up with your veterinarian if things aren’t back to normal at the end of the prescription.
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References
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Grimes, M., et al. (2020). Antibiotics in canine GI disease: When to use and when to ditch. DVM360.
Langlois, D. K., et al. (2019). Metronidazole treatment of acute diarrhea in dogs: A randomized double blinded placebo‐controlled clinical trial. Journal of Veterinary Internal Medicine.
Leib, M. S. (2008). Treatment of chronic idiopathic large-bowel diarrhea in dogs with a highly digestible diet and soluble fiber: A retrospective review of 37 cases. Journal of Veterinary Internal Medicine.
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The United States Pharmacopeial Convention. (2007). Metronidazole (veterinary—systemic).
U.S. Food and Drug Administration. (2023). FDA approves first treatment for Giardia duodenalis in any animal species.
Virbac. (2023). AYRADIA (metronidazole oral suspension) for dogs.
