Metronidazole for Dogs – Dosage, Uses & Side Effects

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Metronidazole is a type of medication that can be prescribed for treating anaerobic bacterial infections or in cases of protozoal infections.

This drug is typically utilized to treat a variety of intestinal problems, including diarrhea, but it works in many types of infections (abscesses and others) whose pathogen is suspected to be an anaerobic bacteria.

But can dogs take Metronidazole, and should you ever consider giving it to your pooch if he has an upset stomach? In this post, we’ll look at how Metronidazole can be used for dogs, its dosage, as well as whether there are any risks associated with it.

What Is Metronidazole Used for in Dogs?

Even though Flagyl (the brand name for this medication) hasn’t been approved by the FDA for use in our canine companions, many veterinarians will recommend the medication for a variety of health problems.

Ideally, the vet should first discover the pathogen that has caused the medical condition and only then prescribe Metronidazole. However, this doesn’t always happen. Vets can use Metronidazole to treat conditions such as inflammation of the lower intestine, diarrhea, sepsis, dental infections, internal abscesses, or bone infections.

It is particularly useful for treating parasitic and bacterial infections ranging from Giardia and Trichomonas to Balantidium coli, for example.

What’s truly unique about Metronidazole is that it is among the few medications in its line that can cross the blood to brain barrier, meaning that it can be utilized for treating nervous system infections, too.

But for the same reason, it can also cause adverse reactions in the central nervous system, and there have been scientific papers published on cases of metronidazole-induced encephalopathy (in humans).

How to Give Metronidazole to Dogs

First of all, do not use Metronidazole on your dog if your vet did not recommend it or didn’t initiate the treatment. It can be a dangerous medication, and it has heaps of side effects that we will discuss in a section below.

However, in case you do forget the dosage that your veterinarian has recommended, here is how you can give your dog Metronidazole safely.

Metronidazole tablets come in doses of 250 or 500 mg per pill. In cases of Giardia, your pet should receive between 7 and 11 mg per pound per day. But the dosage can be increased up to 29 mg per pound.

If your dog has an anaerobic infection, Fido should receive around 11 to 22 mg per pound of bodyweight every 12 hours. The reason for this is that while Metronidazole is an extended-release drug and it works in this way for humans, dogs have a shorter digestive tract and will therefore partially digest the agent before eliminating it.

In any case, have a talk with your veterinarian before deciding to start giving your pooch Metronidazole.

Plus, the vet can also administer it through an injection, which is far better than you having to split the pills, create a powder from them, and then try to figure out the dosage on your own. Besides, they are known for being very bitter, which is why crushing them is a no-go if you want to have a chance of your dog actually taking them. This makes giving your pooch the right dosage even more difficult.

Metronidazole Side Effects in Dogs

Metronidazole toxicity in dogs is relatively low, but we would like to point out that it is not recommended for pregnant dogs or those that are nursing, those that are weak, have liver disorders, are on blood thinners, or have a known allergy to this type of drug or those in its class.

Even though the side effects of metronidazole in dogs are quite rare and the drug is considered to be somewhat safe (when you use the right dosage), adverse reactions can happen. These are the most common ones:

These adverse reactions can happen more or less often in dogs that are undergoing treatment with Metronidazole. However, there are some more serious ones, and they include, but are not limited to the following:

  • Seizures
  • Loss of coordination
  • Eye twitching
  • Tremors
  • Weakness

If you notice any of these signs, get in touch with your veterinarian as soon as possible. Another side effect, but fortunately, one that happens quite rarely is a skin disorder (cutaneous vasculitis). In this condition, the skin blood vessels suffer from inflammation, and that’s how you might notice symptoms such as scaling, swelling, bruising, or the presence of lumps or bumps in your pet’s skin.

While Metronidazole doesn’t usually remain in a dog’s body for more than 24 hours, this might not be the same for pets who have kidney or liver disease. That is why it is not a medication recommended for them.

Drug Interactions

Metronidazole can interact with some types of medications, and they range from chemotherapy drugs to gastro-protectants. It also interacts heavily with certain toxic substances, such as those present in rodenticides (warfarin).

When you take your canine friend to the vet, it is important for you to tell them about any medication that you might be giving your dog or that your dog might have received in the past several days. Otherwise, the vet might prescribe Metronidazole, and it could interact with said medications by accident.

What Happens If You Miss a Dose of Metronidazole?

Absolutely nothing. It goes without saying that it is not an ideal situation, but you shouldn’t worry if this does happen. If you forgot to give your dog a dose, but the next one is close, don’t double the dose — it might have severe consequences on your dog’s health.

However, make sure that this doesn’t happen again. It is highly important for you to give your dog the treatment prescribed as per the veterinarian’s instructions and for the recommended time.


Metronidazole is available as a capsule, liquid suspension, or tablet. It hasn’t been approved by the FDA (at the time this article was written). You should give it to your canine friend only after a vet recommends it and based on their directions solely.

In some dogs, it can cause serious side effects, so it is considered a fairly risky treatment option compared to others. However, its effectiveness in anaerobic bacterial and protozoal infections is undeniable.



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