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Metronidazole for Dogs: How It works, Usage, Safety & Side Effects

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If you’ve ever had a moderate to severe infection or disease, your doctor has likely prescribed or at least discussed prescribing you an antibiotic. Metronidazole is an example of one of these commonly prescribed antibiotics. The drug was initially (and still is) used in humans, but in recent years, more and more veterinarians are accepting Metronidazole as a viable treatment option for their patients as well, namely dogs and cats. 

The term “antibiotic” is a familiar one to some, but we’ll dive deeper into what that really means, and if Metronidazole is right for your dog.

Table of Contents

  1. What is Metronidazole
  2. Usage in Dogs
  3. Safety & Side Effects
  4. FDA Status
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What is Metronidazole? 

As we touched on, Metronidazole is a commonly prescribed antibiotic. Examples of brand name versions of Metronidazole include Flagyl, Metizol, Protostat, and Metrogel. 

How does it work?

If you look up how Metronidazole technically works, you’ll be bombarded with medical jargon and other terms that are difficult to understand for someone without a medical degree (myself included). With that in mind, we’ll try to explain this in a digestible fashion. 

As we now know, the job of an antibiotic is ultimately to eradicate and prevent disease and or infections. Different antibiotics will be used to treat different infections the body. However, Metronidazole in unique from many other antibiotics, as it is able to treat central nervous system infections. It is able to do this by penetrating the blood-brain barrier, ensuring that damaged tissues (infected tissues) receive the proper amount of circulation and oxygen, which is key for recovery. Infected areas of the body are usually low in oxygen, due to the infection itself. Metronidazole helps repair and brings oxygen to these areas and the damaged cells and tissues within

Usage in Dogs

Like most antibiotics, Metronidazole can be prescribed to address a number of different conditions and or infections in humans and dogs. 

In dogs, it is normally used to treat: 

  • Inflammatory Bowel Disease (IBD)
  • Bacterial Infections causing diarrhea or sepsis
  • Oral/Dental infections 
  • Parasite Infection 

Now, these health issues listed above may not cover everything Metronidazole can be potentially used for, but they are certainly the most common. Your veterinarian may decide this antibiotic is effective for another issue your dog is dealing with. 

Safety & Side Effects 

Metronidazole is generally considered very safe by veterinarians. However, as is the case with almost every medication, side effects are possible. 

Common Side Effects

  • Nausea/Vomiting
  • Loss of Appetite 
  • Blood in urine 
  • Fever 
  • Drooling 
  • Gagging 
  • Fatigue 

These side effects are usually moderate if they do occur, but you should alert your veterinarian if your dog displays any of these listed symptoms while taking Metronidazole. It is especially rare, but it is also possible that your dog may have a serious allergic reaction to Metronidazole, involving hives, rashes and rapid heartbeat. If your dog is appearing to have an allergic reaction to the drug, contact your veterinarian immediately. 

Metronidazole is not recommended for dogs with kidney or liver diseases, seizure disorders, and pregnant pets. Pets that are taking Metronidazole for long periods of time may endure more serious side effects

  • Irregular heartbeat 
  • Seizures
  • Dilated Pupils 
  • Tremors 

If your dog is showing any of these symptoms and has been taking Metronidazole for an extended period of time, it should be treated as an emergency situation! Contact your veterinarian right away. 

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FDA Status 

The Food and Drug Administration is responsible for protecting the public health by ensuring the safety, efficacy, and security of veterinary drugs. If you’ve done some of your own research on Metronidazole, you may find it peculiar that it has actually NOT been FDA approved for use in animals (dogs and cats), although it is FDA approved for use in humans. If the FDA hasn’t approved something for use in a certain species, like dogs, it is usually because they do not feel there is enough evidence or need for approval. However, don’t take this as a deal breaker necessarily. Metronidazole is widely accepted and viewed as safe in the veterinary industry. It is fair to feel a little apprehensive giving your dog something that has not been FDA approved, but talk with your veterinarian and see if they can’t ease your initial skepticism. 

Does my dog need it? 

To answer bluntly, hopefully not! Joking aside, if your dog is dealing with a disease of infection listed above, whether it be IBS or a bacterial infection, Metronidazole has been found to be a largely safe and effective antibiotic for dogs. Although studies on dogs specifically may not be broadly available, the data is convincing enough for veterinarians to accept and apply this medication in their practice. If there were any indications that it could be harmful or ineffective, this would not be the landscape. 

With that being said, trust your veterinarian. We can sit here and speculate all day, but in the end, your dog’s doctor will know what’s best, given the situation. But when and if that discussion occurs, hopefully, you now have a loose understanding of what this drug is and how it is meant to help your dog!


The ElleVet Team
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