metronidazole
Metronidazole (Flagyl) is a nitroimidazole antibiotic that’s FDA-approved in humans. Veterinarians also prescribe this medication off-label to treat certain infections in dogs and cats. For pets, metronidazole is given by mouth, typically twice daily. Treatment usually lasts 5 to 7 days. Metronidazole comes as a tablet or capsule.Your veterinarian might recommend for you to go to a compounding pharmacy to have it made into a liquid that’s easier for your pet to take. Some side effects of this medication that your pet might have include gagging, drooling, and reddish-brown urine.
What is Metronidazole for pets?
What is Metronidazole for pets used for?
Giardiasis infection (gut infection) in dogs and cats
Other types of susceptible infections (typically in the liver or gut), such as amebiasis and trichomoniasis, in dogs and cats
Inflammatory bowel disease in dogs and cats
How Metronidazole for pets works
Metronidazole is a nitroimidazole antibiotic. It kills bacteria and parasites by damaging their genetic material. Metronidazole can also help lower inflammation (swelling and pain) in the gut that’s caused by the infection.
Drug Facts
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What are the side effects of Metronidazole for pets?
Common Side Effects
- Reddish brown urine
- Nausea
- Gagging
- Drooling
- Diarrhea
Other Side Effects
- Not eating
- Vomiting
Serious Side Effects
- Serious allergic reaction: hives, fast heart rate, trouble breathing
- Serious skin reaction (cutaneous vasculitis): scaling of the skin, bruises, bumps, purple or red spots, cuts, swelling, hair loss, fever, not eating much
- Symptoms of too much medication: trouble walking, tremors, enlarged pupils, rapid eye movements, twitching, seizures
- Nausea and vomiting that doesn’t get better over time
Source: Prescribing Information
The following side effects have also been reported
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
More common
Agitation
back pain
blindness
blurred vision
burning, numbness, tingling, or painful sensations in the hands or feet
changes in speech patterns
confusion
decreased vision
dizziness
drowsiness
headache
irritability
lack of coordination
seeing or hearing things that are not there
seizures
shakiness and unsteady walk
slurred speech
stiff neck or back
trouble speaking
unsteadiness, trembling, or other problems with muscle control or coordination
unusual tiredness or weakness
vomiting
weakness in the arms, hands, legs, or feet
Less common
Black, tarry stools
blood in the urine
body aches or pain
burning while urinating
chills
clumsiness or unsteadiness
difficulty with breathing
ear congestion
fainting
feeling of pelvic pressure
frequent or painful urination
irregular heartbeat
loss of voice
pinpoint red spots on the skin
skin rash, hives, redness, itching
stomach and back pain (severe)
unusual bleeding or bruising
vaginal irritation, discharge, or dryness not present before taking the medicine
Rare
Bleeding gums
dark urine
fast heartbeat
indigestion
loss of appetite
painful or difficult urination
pains in the stomach, side, or abdomen, possibly radiating to the back
sores, ulcers, or white spots on the lips or in the mouth
swollen glands
yellow eyes or skin
Incidence not known
Blistering, peeling, or loosening of the skin
bloody or cloudy urine
burning while urinating
continuing diarrhea
continuing stomach pain
feeling of warmth
increased volume of pale, dilute urine
joint or muscle pain
loss of bladder control
red skin lesions, often with a purple center
red, irritated eyes
redness of the face, neck, arms, and occasionally, upper chest
redness of the skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Dizziness or lightheadedness
feeling of constant movement of self or surroundings
sensation of spinning
stomach cramps
trouble sleeping
Rare
Change in taste sensation
congestion
pain or tenderness around the eyes and cheekbones
tender, swollen glands in the neck
trouble with swallowing
unpleasant or sharp metallic taste
voice changes
Incidence not known
Decreased interest in sexual intercourse
inability to have or keep an erection
loss in sexual ability, desire, drive, or performance
painful sexual intercourse
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Pros and cons of Metronidazole for pets
Pros
Taken by mouth, so easier to give to pet at home compared to an injection
Pills can be made into an oral liquid by a compounding pharmacy
Treatment generally lasts 5 to 7 days
Cons
Typically given twice daily
Bitter taste, so can be challenging to give to pet
Not for dogs and cats that are pregnant or nursing
Pharmacist tips for Metronidazole for pets
It’s important to give your pet the full course of the antibiotic treatment with metronidazole as directed by their veterinarian. Stopping treatment early can cause their infection to come back and become more difficult to treat.
Metronidazole tablets have a bitter taste that your pet might not like. Ask your veterinarian about ways to give this antibiotic to your dog or cat. They might recommend that you hide it in pill pockets, which are treats for pets with a place to put the medication in the middle. Or, ask your veterinarian if it’s appropriate to hide it in any other snacks that your pet likes.
If your pet is having a hard time taking the pill form of metronidazole, ask your veterinarian if it’s appropriate for you to get a liquid version made at a compounding pharmacy. Sometimes, it might be easier to give a pet the liquid version than the pill form.
Metronidazole can cause your pet’s urine to turn a reddish-brown color. This is an expected side effect and isn’t harmful to your pet. This side effect will go away after your pet finishes their course of metronidazole.
If your pet continues to have diarrhea after taking metronidazole, let your veterinarian know. While metronidazole is helpful for treating diarrhea caused by certain parasites, it’s not appropriate for all cases of diarrhea. If this medication isn’t working well, your veterinarian can let you know about other treatment options.
Wash your hands after giving metronidazole to your pet. And don’t let your pet lick you right after they take their dose. Some people might be sensitive to metronidazole and getting this medication on the skin can lead to rash.
Frequently asked questions about Metronidazole for pets
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What are the risks and warnings for Metronidazole for pets?
Metronidazole can cause some serious health issues. This risk might be even higher for certain pets. If this worries you, talk to your veterinarian about other options.
Risk of serious neurologic effects
Risk factors: Taking higher doses of metronidazole | Taking metronidazole for a longer period of time | Pets who have seizures
If the dose of metronidazole is too high for your dog or cat, it can cause serious neurological side effects, including movement problems, tremors, seizures. The risk is higher for pets that already have seizure conditions or are taking seizure medications. Let your veterinarian know right away if you notice these symptoms in your pet so they can let you know about the next steps.
Possible medication interactions
Based on how metronidazole works in the body and data from human studies, there’s a risk that it can interact with certain medications, including cimetidine (Tagamet), warfarin (Coumadin), and certain seizure medications. Let your veterinarian know about all the medications your pet is taking before starting metronidazole. Your veterinarian can help you check for possible interactions with metronidazole to keep your pet safe.
Not for dogs and cats that are pregnant or nursing
Metronidazole shouldn’t be given to dogs and cats that are pregnant or nursing. Though studies are limited, there’s a risk that this medication can cause serious harm during pregnancy. Metronidazole can also pass into mother’s milk and cause harm to nursing puppies or kittens. If your cat or dog is pregnant or nursing, let your veterinarian know. They can talk with you about options for your pet.
Use with caution in animals with liver or kidney problems
Let your veterinarian know if your dog or cat has liver or kidney problems. Metronidazole is mainly processed through the liver, and cleared from the body through both the liver and kidney. If your pet’s liver or kidney isn’t working well, they’re more likely to experience side effects. In some cases, the veterinarian will consider giving your pet a lower dose of metronidazole.
Risk of serious skin condition
Though rare, pets that take metronidazole might experience a serious skin reaction called cutaneous vasculitis. This condition is caused by inflammation of the blood vessels. Get medical help right away if you notice symptoms of this skin reaction in your pet, such as cuts and bruises on the skin, purple or red spots on the skin, and fever. They might need more medical attention.
Metronidazole dosage forms
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 59ml of 0.75% | 1 bottle | $56.29 | $56.29 |
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 375mg | 14 capsules | $25.53 | $1.82 |
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 55g of 1% | 1 pump | $30.00 | $30.00 |
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 70g of 0.75% gel | 1 package | $23.50 | $23.50 |
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 45g of 0.75% | 1 tube | $22.45 | $22.45 |
Typical dosing for Metronidazole for pets
Your veterinarian generally determines the dose of metronidazole for your cat or dog based on their body weight. But the dose can differ depending on other factors, such as your pet’s health condition or the type of infection the veterinarian thinks your pet has.
An example of possible dosing:
Dogs and cats: The typical dose is 15 mg/kg by mouth every 12 hours.
Interactions between Metronidazole and other drugs for pets
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Amprenavir
- Bepridil
- Cisapride
- Disulfiram
- Dronabinol
- Dronedarone
- Mesoridazine
- Pimozide
- Saquinavir
- Sparfloxacin
- Terfenadine
- Thioridazine
- Ziprasidone
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Alfuzosin
- Amiodarone
- Amitriptyline
- Anagrelide
- Apomorphine
- Aripiprazole
- Aripiprazole Lauroxil
- Arsenic Trioxide
- Asenapine
- Astemizole
- Atazanavir
- Azithromycin
- Bedaquiline
- Buprenorphine
- Bupropion
- Buserelin
- Busulfan
- Capecitabine
- Ceritinib
- Chloroquine
- Chlorpromazine
- Cholera Vaccine, Live
- Ciprofloxacin
- Citalopram
- Clarithromycin
- Clofazimine
- Clomipramine
- Clozapine
- Crizotinib
- Cyclobenzaprine
- Dabrafenib
- Dasatinib
- Degarelix
- Delamanid
- Desipramine
- Deslorelin
- Deutetrabenazine
- Disopyramide
- Dofetilide
- Dolasetron
- Domperidone
- Donepezil
- Doxepin
- Doxifluridine
- Droperidol
- Ebastine
- Efavirenz
- Encorafenib
- Entrectinib
- Eribulin
- Erythromycin
- Escitalopram
- Famotidine
- Felbamate
- Fingolimod
- Flecainide
- Fluconazole
- Fluorouracil
- Fluoxetine
- Formoterol
- Foscarnet
- Fosphenytoin
- Galantamine
- Gatifloxacin
- Gemifloxacin
- Glasdegib
- Gonadorelin
- Goserelin
- Granisetron
- Halofantrine
- Haloperidol
- Histrelin
- Hydroquinidine
- Hydroxychloroquine
- Hydroxyzine
- Ibutilide
- Iloperidone
- Imipramine
- Inotuzumab Ozogamicin
- Itraconazole
- Ivabradine
- Ivosidenib
- Ketoconazole
- Lapatinib
- Levofloxacin
- Lofexidine
- Lumefantrine
- Macimorelin
- Mebendazole
- Mefloquine
- Methadone
- Mifepristone
- Mizolastine
- Moxifloxacin
- Mycophenolate Mofetil
- Mycophenolic Acid
- Nafarelin
- Nelfinavir
- Nilotinib
- Norfloxacin
- Octreotide
- Ofloxacin
- Olanzapine
- Ondansetron
- Osimertinib
- Oxaliplatin
- Ozanimod
- Paliperidone
- Panobinostat
- Papaverine Hydrochloride
- Paroxetine
- Pasireotide
- Pazopanib
- Pentamidine
- Perphenazine
- Pimavanserin
- Pipamperone
- Pitolisant
- Ponesimod
- Posaconazole
- Probucol
- Procainamide
- Prochlorperazine
- Promethazine
- Propafenone
- Protriptyline
- Quetiapine
- Quinidine
- Quinine
- Ranolazine
- Ribociclib
- Risperidone
- Ritonavir
- Selpercatinib
- Sertindole
- Sertraline
- Sevoflurane
- Siponimod
- Sodium Phosphate
- Sodium Phosphate, Dibasic
- Sodium Phosphate, Monobasic
- Solifenacin
- Sorafenib
- Sotalol
- Sulpiride
- Sunitinib
- Tacrolimus
- Tamoxifen
- Tegafur
- Telaprevir
- Telavancin
- Telithromycin
- Tetrabenazine
- Tolterodine
- Toremifene
- Trazodone
- Trimipramine
- Triptorelin
- Vandetanib
- Vardenafil
- Vemurafenib
- Venlafaxine
- Vilanterol
- Vinflunine
- Voclosporin
- Voriconazole
- Vorinostat
- Warfarin
- Zuclopenthixol
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Carbamazepine
- Cholestyramine
- Cyclosporine
- Lithium
- Milk Thistle
How much does Metronidazole cost?
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References
Best studies we foundAmerican College of Veterinary Ophthalmologists. (2020). How to give medicine to your pet by mouth.
American College of Veterinary Pharmacists. (n.d.). Metronidazole.
American Veterinary Medical Association. (n.d.). Compounding FAQ for pet owners.
Caneschi, A., et al. (2023). The use of antibiotics and antimicrobial resistance in veterinary medicine, a complex phenomenon: A narrative review. Antibiotics.
Centers for Disease Center and Control. (2024). Antimicrobial resistance in people and animals.
Centers for Disease Control and Prevention. (2024). About Giardia and pets.
Dowling, P. M., et al. (2024). Drugs used to treat inflammatory bowel disease in monogastric animals. Merck Manual Veterinary Manual.
Horniman, N. (2023). Eight tips to give your clients when giving medicine to a reluctant pet at home. Improve Veterinary Practice.
Innerå, M. (2013). Cutaneous vasculitis in small animals. The Veterinary Clinics of North America: Small Animal Practice.
Mercer, M. A. (2024). Nitroimidazoles use in animals. Merck Manual Veterinary Manual.
Rebuelto, M., et al. (2010). Antibiotic treatment of dogs and cats during pregnancy. Veterinary Medicine International.
Roberts, J. (2025). Entamoeba histolytica amebiasis. Merck Manual Veterinary Manual.
United States Pharmacopeial Convention. (2007). Metronidazole (veterinary–systemic).
Virbac AH Inc. (2023). Ayradia- metronidazole solution [package insert]. DailyMed.
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