What is Metronidazole?

  • Metronidazole is the primary antibiotic drug used by veterinarians in the treatment of inflammation in the large intestine and other diseases in dogs.
  • Despite being the mainstay medicine, metronidazole is not 100% effective, as anaerobic infections can still reoccur after treatment(1).
  • A 2014 study reveals that herbal therapy can be just as effective as metronidazole in treating anaerobic bacteria overgrowth in the intestine(2).
  • Cannabidiol or CBD is seen as a potential and natural alternative to antibiotic drugs due to its inherent anti-inflammatory properties(3).

What Is Metronidazole Used For?

Metronidazole is an antibiotic drug veterinarians commonly use to treat inflammatory bowel disease in dogs. It is widely known through the brand name Flagyl and is also applicable to other conditions in canines, cats, and horses. 

Veterinarians often combine metronidazole with other antibiotics. The low molecular weight of this antiprotozoal medicine allows for rapid and effective absorption by the body through oral and intravenous applications.

Metronidazole Guidelines

Doctors consider the use of metronidazole as a safe medicine for cats and dogs. However, they do not prescribe this to pregnant females and puppies.

The drug can also have harmful effects on pets that have liver disease, kidney diseases, neutropenia, and seizures(4).

Owners need to consult with their local veterinarian before administering metronidazole to their pets. They should also inform their doctors regarding any other medications their dog is taking and the medical conditions they may have. 

Treating most bacterial infections in dogs using metronidazole is considered off-label. Hence, owners must follow the directions of their veterinarians carefully(5).

Vet Use for Metronidazole

Metronidazole is available in tablet, capsule, and liquid form. It can also be prescribed as metronidazole benzoate, which is a less bitter formulation than its counterparts and makes it easier to consume.

Veterinarians can also apply the drug as an injectable, which they will perform in a veterinary hospital or clinic(6).

Metronidazole Dosage for Dogs Information

Suggested dosage on metronidazole for dogs will depend on its intended long-term use alongside specific information regarding the case of a pet. Typically, veterinarians apply a dose range between 5 to 25 mg/lb, which is then given by mouth.

Lower dosages are generally taken twice a day, while high doses may be provided once daily(7).

Metronidazole in liquid forms should be shaken well before being administered. A metronidazole tablet should not be crushed since the bitterness can make it difficult for pets to swallow. 

Pet owners must understand how metronidazole works and follow specific dosing instructions from their veterinarian to avoid complications. 

Side Effects of Metronidazole

A 2018 study by the Australian Veterinary Association shows that metronidazole can cause neurotoxicity in dogs(8). This type of toxicity has an adverse effect on the function or structure of the peripheral or central nervous system.

Neurotoxic effects are rare, but in case they happen, it can manifest in the form of paralysis or allergic reactions in canines. Other common side effects in dogs include:

  • Nausea
  • Diarrhea
  • Drooling
  • Fatigue
  • Gagging
  • Loss of appetite
  • Fever
  • Blood in urine
  • Difficulty breathing

Excess application of metronidazole in dogs can also cause tremors, stiffness, dilated pupils, and abnormally slow heartbeat. In case any of these happen, a pet will require emergency veterinary attention immediately(9).

Natural Alternatives to Metronidazole for Dogs

Protozoal infections that are caused by the parasites giardia and trichomonas in dogs are prevalent. Its clinical signs include discomfort, vomiting, and small bowel diarrhea, among others.

Controlling these diseases in dogs has become a problem for many small animal owners and veterinarians. Although doctors recommend veterinary medicine like metronidazole, they are not 100% effective since superinfections still happen regularly(10).

A study from the Global Advances in Health and Medicine states that herbal therapy can be just as effective as metronidazole in treating bacterial overgrowth in the gastrointestinal tract(11). This statement opens up other options for animal owners with regards to the treatments available for their canines.

CBD as a Natural Alternative

One noteworthy and natural alternative to metronidazole for dogs is cannabidiol (CBD). 

CBD is a chemical derived from the Cannabis sativa plant and is known for its numerous health benefits to both humans and pets. 

A study in 2019 investigated the antibacterial effects of cannabidiol and found that its drug interactions increase antibiotic effects when used together with selected antibiotics(12).

Dr. Jerry Klein, the Chief Veterinary Officer of American Kennel Club (AKC), said that dogs could benefit from using CBD oil because of the product’s anti-inflammatory properties(13).

A 2010 study also states that cannabinoids have sufficient anti-inflammatory properties and a mechanism of action that is potent enough to help regulate the immune system(14).

But despite the evidence, the risks that come with using CBD on dogs have not yet been researched in-depth. There is also no approval from the FDA on the use of CBD-based products for pets, and there is no dosing chart issued as of now(15).


Metronidazole may be the mainstay drug in the duration of treatment for certain diseases in dogs, but it is not 100% effective as a cure. 

The studies on CBD show that it can be a potential alternative to metronidazole for dogs. Its therapeutic properties may be a safer and more natural option for pet owners.

Despite these claims, it is always best for owners to consult a veterinarian to avoid problems.

  1. Fiechter R, Deplazes P, Schnyder M. Control of Giardia infections with ronidazole and intensive hygiene management in a dog kennel. Vet Parasitol. 2012 Jun 8;187(1-2):93-8. doi: 10.1016/j.vetpar.2011.12.023. Epub 2011 Dec 23.
  2. Victor Chedid, Sameer Dhalla, John O. Clarke, Bani Chander Roland, Kerry B. Dunbar, Joyce Koh, Edmundo Justino, Eric Tomakin, and Gerard E. Mullin. Herbal Therapy Is Equivalent to Rifaximin for the Treatment of Small Intestinal Bacterial Overgrowth. Glob Adv Health Med. 2014 May; 3(3): 16–24. Published online 2014 May 1. doi: 10.7453/gahmj.2014.019
  3. Kosgodage US, Matewele P, Awamaria B, Kraev I, Warde P, Mastroianni G, Nunn AV, Guy GW, Bell JD, Inal JM, Lange S. Cannabidiol Is a Novel Modulator of Bacterial Membrane Vesicles. Front Cell Infect Microbiol. 2019 Sep 10;9:324. doi: 10.3389/fcimb.2019.00324. eCollection 2019.
  4. AKC Staff (2016, January 04). Metronidazole for Dogs. Retrieved from https://www.akc.org/expert-advice/health/metronidazole-for-dogs/.
  5. Rania Gollakner (2018). Metronidazole. Retrieved from https://vcahospitals.com/know-your-pet/metronidazole.
  6. ibid.
  7. PetMD Editorial (2012, November 07). Metronidazole for Dogs and Cats. Retrieved from https://www.petmd.com/pet-medication/metronidazole.
  8. Tauro A1, Beltran E2, Cherubini GB3, Coelho AT3, Wessmann A4, Driver CJ1, Rusbridge CJ1,5. Metronidazole-induced neurotoxicity in 26 dogs. Aust Vet J. 2018 Dec;96(12):495-501. doi: 10.1111/avj.12772.
  9. AKC Staff. op.cit.
  10. Fiechter, Deplazes, Schnyder. op.cit
  11. Chedid V et al. op. cit.
  12. Kosgodage US et al. op. cit.
  13. Randa Kriss (2019, October 27). CBD Oil for Dogs: What You Need to Know. Retrieved from https://www.akc.org/expert-advice/health/cbd-oil-dogs/.
  14. Pisanti S, Malfitano AM, Ciaglia E, Lamberti A, Ranieri R, Cuomo G, Abate M, Faggiana G, Proto MC, Fiore D, Laezza C, Bifulco M. Cannabidiol: State of the art and new challenges for therapeutic applications. Pharmacol Ther. 2017 Jul;175:133-150. doi: 10.1016/j.pharmthera.2017.02.041. Epub 2017 Feb 22.
  15. Kriss R op. cit.
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