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What is Metronidazole and When Should I Use it on My Dog?

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Doctor DebVerified

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Veterinary Medicine

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Metronidazole Uses

Metronidazole is mostly for dogs suffering from inflammatory bowel disease. It is also used to treat nonspecific diarrheal disorders, infections caused by Giardia, and even periodontal disease.

Metronidazole is a prescription only medication classified as an antiprotozoal and antibiotic. This means that the medicine fights both protozoa (simple organisms) and anaerobes (organisms that don’t need air). Metronidazole has multiple prescription names such as Metizol, Flagyl, Protostat, and Metrogel.

A worried dog hides under a blanket

Metronidazole is often prescribed for dogs with inflammatory bowel syndrome, diarrhea, and periodontal disease (gum disease). Veterinarians may also use it for dogs who display signs of bacterial infection or liver issues, as well as for dogs with internal parasites.

How metronidazole works

Metronidazole works by destroying infectious organisms that can attack a dog’s intestinal tract or central nervous system, although scientists don’t understand the exact mechanism of action in the drug. Metronidazole is taken up by anaerobic organisms when it’s introduced into the dog. Inside the organisms, it is reduced to a compound. It is believed that this compound is responsible for the drug’s antimicrobial activity by disrupting DNA and nucleic acid synthesis in the bacteria.

Metronidazole usage and dosing information

The proper dosage depends on several aspects, the dog’s age, weight, and size, and the condition for which the dog is being treated. Your veterinarian can provide the proper dosage information for your dog, as seizures and neurological problems can occur if the dose is too high or is given long term. If your dog is showing these signs, call your veterinarian.

The tablet form tends to be bitter, so prepare yourself for the unpleasant experience of trying to coax your dog to take it. Some sources advocate crushing up the tablets and mixing with food; try this at your own peril, however, as some dogs will refuse to take any food that tastes bitter. You may have more luck stuffing the pill inside a treat, like a piece of cheese, a hotdog, or a meatball. Metronidazole is also available in a compounded flavored pill which many vets carry.

A dog awaits his food being filled

Always administer metronidazole at the same time every day to avoid a missed dosage.

Side effects of metronidazole

Most of the side effects associated with metronidazole – drooling , gagging and pawing at the mouth – happen because the dog does not like the taste of a crushed pill. If you succeed in hiding a whole pill inside food for your dog, she should not experience any of this discomfort. As it stands, it generally lasts for a short time.

Common side effects:

  • Vomiting
  • Lack of appetite
  • Diarrhea
  • Energy loss

Rare but serious side effects:

  • Balance issues
  • Slow irregular heartbeat
  • Dilated pupils
  • Muscle stiffness
  • Seizures
  • Bloody urine

Although extremely rare, it is possible for dogs to have allergic reactions to this drug, including rashes, hives, difficulty breathing, or swelling. Contact a veterinary Expert if you see severe or adverse reactions like these.

Neurotoxicity caused by metronidazole

Dogs who are given metronidazole for extended periods of time may experience signs of neuropathy, or nerve damage, in the ears and feet. A significant overdose can also cause neurological problems.

Signs of neurotoxicity consist of appetite loss, vomiting, lack of balance, rapid eye movement, disorientation, muscle stiffness, and seizures. If your dog is has any of these symptoms, contact a veterinarian immediately.

Metronidazole food and drug interactions  

Veterinarians have used this medication extensively for a number of years to treat many types of canine illnesses. Still, metronidazole has not been approved by the Food and Drug Administration (FDA) for use in dogs.

A small cluster of white and yellow pills

Most vets do not recommend administering metronidazole to puppies, pregnant, or nursing dogs. This medicine may have ill effects on unborn fetuses.

Harmful drug interactions with metronidazole include Tagamet, Dilantin, Warfarin, and Phenobarbital. While this is not a comprehensive list of drug interactions, you will need to advise the veterinarian of all medications your dog taking or allergic to.

Consult a veterinary Expert if you suspect your dog has overdosed of metronidazole. For emergencies call American Society for the Prevention of Cruelty to Animals (ASPCA) Poison control hotline (888-426-4435).

Forgetting a dose of metronidazole

If you notice you have accidentally missed a dose, contact an Expert to get instructions. Never give your dog a double dose of metronidazole. Double dosing may cause dogs to develop significant adverse reactions.

Metronidazole storage and disposal information                       

Metronidazole tablets, or extended-release capsules, must be kept at room temperature, in a tightly closed container. Keep liquid forms refrigerated. Keep out of the reach of children and pets. Your pharmacist or veterinarian can dispose of any medication that is outdated or no longer usable. Do not use outdated medications.

Metronidazole can treat many forms of infections in dogs. Watch for any changes in your dog while taking this medication. Always follow your veterinarian’s instructions and do not self-medicate your dog. For other medical questions about your dog, ask a veterinary Expert.

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