It is a human medicine. A vet may still prescribe it for a dog or cat, which is legal and common, but it means no company has proved to the FDA that it works or is safe in that animal, and there is no approved animal dose to look up. Ask your vet what they expect it to do and what to watch for.
The label says, word for word:
Human label: "FLAGYL 375 capsules are indicated in the treatment of serious infections caused by susceptible anaerobic bacteria." (other label indications: Symptomatic Trichomoniasis, Asymptomatic Trichomoniasis, Treatment of Asymptomatic Sexual Partners, Amebiasis). There is no FDA-approved metronidazole label for dogs or cats.
FLAGYL 375 capsules are contraindicated in patients with a prior history of hypersensitivity to metronidazole or other nitroimidazole derivatives. Do not administer metronidazole to patients who have taken disulfiram within the last two weeks. Discontinue consumption of alcohol or products containing propylene glycol during and for at least three days after therapy with metronidazole.
Boxed warning: Metronidazole has been shown to be carcinogenic in mice and rats (see PRECAUTIONS). Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.
Cases of encephalopathy and peripheral neuropathy (including optic neuropathy) have been reported with metronidazole. Encephalopathy has been reported in association with cerebellar toxicity characterized by ataxia, dizziness, and dysarthria.
Convulsive seizures have been reported in patients treated with metronidazole.
Cases of aseptic meningitis have been reported with metronidazole.
Patients with hepatic impairment metabolize metronidazole slowly, with resultant accumulation of metronidazole in the plasma.
Every approved medicine has a field study behind it, and the label prints what happened:
Human label: "The most common adverse reactions reported have been referable to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; abdominal cramping; and constipation." "A sharp, unpleasant metallic taste is not unusual." (no percentages given)
Metronidazole is a human prescription drug ("Rx only"); no FDA-approved animal drug containing metronidazole was found on DailyMed or fda.gov in this research, and there is no FDA-approved metronidazole product for dogs or cats. Veterinarians may prescribe it extra-label under AMDUCA. FDA: "Congress enacted the Animal Medicinal Drug Use Clarification Act (AMDUCA), adding provisions to the Federal Food, Drug, and Cosmetic Act (FD&C Act) that give veterinarians the legal ability - with certain restrictions - to use approved human and animal drugs in an extra-label manner."
The emergency page sorts the signs by how long you have, and the symptom checker asks what you are seeing. Reactions to a medicine can also be reported to the FDA yourself: how to report a problem.
These answers come from the approved label on DailyMed, read on 2 October 2026. Where the label does not say, the answer says so, and the vet or the pharmacist is the one to ask.
The approved use is quoted at the top of this page. The label read for these answers is the one for FLAGYL capsules, a human prescription medicine. It lists infections in people and does not mention dogs or cats, so ask the vet what it has been prescribed for in your pet.
The label gives no time for a pet. In its study in healthy adults, the level in the blood peaked on average 1.6 hours after capsules taken on an empty stomach. It also tells patients that it is common to feel better early in the course and that the medicine should still be taken exactly as directed.
The label gives doses for people only, so the amount and the timing for your pet come from the vet. It does not say whether to give the capsules with food. It reports that food makes the peak in the blood lower and later without changing how much is absorbed.
The label does not say what to do about a missed dose. Call the clinic or the pharmacy before you give the next one. It does say that skipping doses or not finishing the full course may make the treatment work less well and make it more likely that bacteria become resistant.
The studies and the warnings are quoted above. This label is written for people. It tells patients to stop the capsules immediately and get medical attention if any kind of rash appears. It also says that new signs in the nervous system call for a prompt decision on whether to go on with the medicine. The signs it describes include unsteadiness, dizziness, numbness or tingling in a limb and seizures. For a pet that decision is the vet's, so call the clinic if you see anything like this.
The label says to store the capsules at room temperature, between 59° and 77°F, in a well-closed container with a child-resistant cap.
The FDA says the best way to get rid of most unused or expired medicines is a take-back option: a drug take-back location, which can be at a pharmacy or a police station, or a prepaid mail-back envelope. If you cannot use one, the FDA says a medicine that is not on its flush list can go in the trash at home. Its steps are to mix the medicine with something unappealing such as dirt, cat litter or used coffee grounds, without crushing it, and to seal the mixture in a plastic bag before throwing it away. Flushing is only for medicines on that list, such as opioids. Do not give leftovers to another pet.
Write the dose, the times and the stop date here, then print this page for the fridge.
Dose and times: _____________________________________________
Stop date: _____________________________________________