Metronidazole for Pets
Metronidazole is an antibacterial and antiprotozoal medication veterinarians may prescribe for dogs and cats. It is commonly used for certain anaerobic infections and some intestinal protozoal diseases, and owners should follow their veterinarian’s directions closely because use in pets is typically extra-label in the U.S.
Quick Facts About Metronidazole
Drug class
Nitroimidazole antimicrobial with antibacterial and antiprotozoal activity.
Common brand names
Flagyl® is a common human brand name; veterinary prescriptions may also use compounded formulations.
Available forms
Commonly dispensed as tablets, capsules, and liquid suspension; injectable forms may be used in the hospital.
Species used in
Dogs and cats most commonly; in the U.S., use in pets is generally extra-label and not approved for food-producing animals.
What Metronidazole Is Used For
Metronidazole is used in veterinary medicine to treat certain anaerobic bacterial infections and some protozoal infections, including Giardia and Trichomonas in appropriate cases. Veterinarians may also prescribe it for select gastrointestinal conditions when they believe it is appropriate for the individual pet. It works by damaging the DNA of susceptible organisms, which helps kill certain anaerobic bacteria and protozoa. Because it does not treat every cause of diarrhea, your veterinarian may recommend testing or other treatments instead of, or in addition to, metronidazole.
Side Effects to Watch For
Most side effects involve the digestive system, but neurologic side effects can happen and require prompt veterinary attention.
- Common side effects can include nausea, vomiting, diarrhea, drooling, decreased appetite, and tiredness.
- The medication tastes very bitter, so pets may salivate or resist taking it if a tablet is crushed or a dose is tasted.
- More serious signs can include wobbliness, poor coordination, tremors, eye twitching, weakness, or seizures.
- Rare but important concerns include liver-related problems such as loss of appetite with yellowing of the eyes, skin, or gums, and uncommon blood or skin reactions.
- Call your vet promptly if side effects are severe, persistent, or seem to be getting worse.
Dosing & Administration
Always follow your vet’s instructions exactly. Metronidazole is commonly given by mouth, often with food to help reduce stomach upset. Shake liquid formulations well before use, and ask your veterinary team how to measure each dose accurately. Do not crush tablets unless your veterinarian or pharmacist specifically tells you to, because the medication is very bitter and can be hard for pets to take. If your pet is difficult to medicate, ask your vet whether a different formulation or a compounded product is appropriate. If you miss a dose, give it when you remember unless it is almost time for the next scheduled dose; then skip the missed dose and return to the normal schedule. Do not give two doses at once unless your veterinarian specifically tells you to.
When to Call a Vet
Go to the ER now
- ● Signs of an allergic reaction such as facial swelling, hives, trouble breathing, or collapse.
- ● Possible overdose or toxicity, especially tremors, severe stumbling, muscle spasms, eye twitching, or seizures.
- ● Sudden severe weakness, collapse, or unresponsiveness after a dose.
See a vet within 24 hours
- ● Repeated vomiting, severe diarrhea, or refusal to eat after starting the medication.
- ● Persistent drooling, marked lethargy, or worsening stomach upset.
- ● Yellowing of the eyes, gums, or skin, or any new bruising or unusual skin changes.
- ● Any wobbliness or balance problems, even if mild.
Watch at home, call if it worsens
- ● Mild temporary nausea or softer stool shortly after starting the medication.
- ● Brief decreased appetite or mild tiredness if your pet is otherwise acting normally.
- ● Mild salivation related to the medication’s bitter taste.
Metronidazole FAQs
Can I give my dog human metronidazole?
What happens if I miss a dose?
Can my cat take metronidazole?
How long does metronidazole take to work?
Is metronidazole still commonly used for diarrhea in pets?
Sources
- Plumb’s Veterinary Drugs / Plumb’s Veterinary Drug Handbook
- Merck Veterinary Manual — Nitroimidazoles Use in Animals
- VCA Animal Hospitals — Metronidazole
- Metronidazole (Flagyl) for Dogs: Uses, Dosage & Side Effects — SpectrumCare
- Spectrum Care — Metronidazole for Cats: Uses, Dosage & Side Effects — Spectrum Care
Disclaimer: The information provided in this article is for educational purposes only and does not constitute veterinary medical advice. Reading this content does not establish a veterinarian-client-patient relationship. Every pet is different — always consult a licensed veterinarian before making decisions about your pet's health, diet, or care. If you'd like personalized guidance, you can talk to one of our vets. If your pet is experiencing a medical emergency, contact your local emergency animal hospital immediately.