What Is It Like to Give Your Cat the Antibiotic Metronidazole

GoodRx Health

For cats, metronidazole (Flagyl) is an antibiotic that's commonly used to treat certain types of infections caused by bacteria and single-celled parasites.

Your cat may need to take metronidazole to address digestive tract problems, such as diarrhea and inflammation associated with conditions like inflammatory bowel disease (IBD). Metronidazole is known by its full name, but it's sometimes referred to simply as "metro" and is sold under the brand name Flagyl.

Here's how three cat owners describe what to expect if you have to give your cat metronidazole.

The antibiotic is not miraculous, but it's helpful

Ari Holmes, who lives in the Atlanta area, lost her beloved senior cat, Gator, in 2020.

Gator had a complicated medical case with issues including chronic diarrhea, early kidney failure, arthritis, and nausea. Ari took Gator to the vet for an abdominal ultrasound, thinking that there might be more going on with her cat than renal failure. One theory was that Gator had inflammatory bowel disease, and another theory suspected small cell lymphoma. About a month before the ultrasound, Gator took a round of metronidazole for his diarrhea.

"For cats, it's really good for intestinal inflammation," says Ari, who is 44 and now has five cats.

Since Gator was extremely sensitive to medications, he was prescribed half the usual dose of metronidazole. The results weren't dramatic, but decent, Ari says.

Ari Holmes is pictured in a snapshot with her cat.

"It didn't clear it up, but it helped a little bit," Ari says. "He had so much going on at that point. If I had to do it again, I would let him go sooner. He was pretty uncomfortable by the end. I was trying to give him the best and longest life that I could, and we were so attached to each other."

Unlike many cat owners who face the wrath of kitties who can't stand the bitter taste of liquid "metro," Ari used a pill form, and Gator took it fairly easily.

When all else fails, it can do the trick

Renee Emerson of Walnut Creek, California, is a board member of Community Concern for Cats, a cat rescue group in Northern California. She manages many of the 300 or so kittens and cats that come into foster care. The group's protocol is to use metronidazole for kittens with diarrhea only after treating them with other remedies.

First, they give a deworming treatment with pyrantel pamoate. Then, if that doesn't take care of the diarrhea, they give them fenbendazole (Pamacur). If neither treatment works, Renee says, they use metronidazole - which is effective, but potent.

"We tend to hold it back because it wipes out the gut flora, and it takes a while to build that back," Renee says, referring to the tiny organisms in a cat's stomach that help with digestion, nutrient absorption, and overall health. "But it takes care of the diarrhea that the other treatments can often not make any difference with."

Renee Emerson is pictured in a snapshot with two kittens.

Experience has taught Renee, who is 63 and has three cats of her own, that "sometimes metro works and sometimes not," she says. "But in almost every scenario we see, it really is the lucky charm."

Renee has not observed any side effects from metronidazole. But since it kills off good gut bacteria, in addition to what causes the infection, she recommends giving your cat a probiotic, like Nexabiotic, after a course of metro so that your cat's gut flora can rebuild.

She also has some advice for administering it. She holds the back of her cat's neck firmly, because she says if they hate getting a dose, they'll squirm and try to run. And to counteract the bitter taste, she gives the medication before a meal or mixes it with a cat treat.

It can help with kitty digestive problems

Pam Amicarella, a 61-year-old independent cat rescuer from the Pittsburgh area, recalls how her beloved 10-year-old cat Angel was just a sweet white kitten, and also one of her rescues.

She says Angel, one of three stray kittens she rescued from under a shed, came down with a horrendous case of diarrhea about 3 months after she brought the kittens home for foster care.

"There was no form or shape. She was literally leaking everywhere," Pam recalls. "It was gross, being a white cat. It was almost like Hershey syrup. She had to be crated up."

Pam Amicarella is pictured in a snapshot with her cat.

Angel's messy ordeal ended quickly after Pam took the kitten to the veterinarian, who prescribed metronidazole and fluids. Within a day, Angel's bowel movements started firming up. And within 3 to 4 days, the sick kitten was back to normal.

To get Angel to cooperate, Pam says she had to wrap the kitten up like a burrito and administer the liquid medication with a syringe.

Although Pam has cared for hundreds of cats and kittens over the years, Angel's case is the only one where a kitty was prescribed metronidazole. Usually, she gives foster cats worming treatments when she brings them home, and that prevents a lot of diarrhea. Still, if she encountered another severe case of kitty diarrhea, Pam says metronidazole would definitely be her go-to treatment, and she would ask her veterinarian for it.

What does the veterinarian say?

Ghanasyam Bey, DVM

Veterinary Reviewer

Metronidazole is a common antibiotic that treats many causes of diarrhea in cats. It has both antibiotic and anti-inflammatory properties. Some conditions veterinarians prescribe metronidazole for in cats include:

• Inflammatory bowel disease

• Bacterial diarrhea

• Some parasitic forms of diarrhea

Metronidazole works by killing bacteria or parasitic organisms and/or by reducing inflammation in the intestinal tract. It tends to work quickly. Often improvement can be noted in as little as 24 hours. You may notice the diarrhea starting to become more formed and less frequent within one day, but some cats may take a few days to respond and a week or more to fully recover.

Side effects are uncommon and usually minor, and can include increased drooling or, in less likely cases, decrease in appetite, gagging, or nausea. More serious side effects are rare and generally only occur if metronidazole is taken at higher than usual doses for extended periods of time.

Most courses of metronidazole treatment are 5 to 7 days, but duration of treatment can vary depending on the condition being treated.

It is important to always finish the entire course prescribed to make sure the treatment has the desired effect and does not contribute to medication resistance. It is also important to note that metronidazole is prescribed only in certain cases, and there may be better medications for the diarrhea depending on the cause.

Also, because of the nature of the medication, it can affect both good and bad bacteria in the intestinal tract, so it is used ideally only as needed and sometimes with a probiotic.

Metronidazole is convenient because it's available as a tablet or oral (by mouth) liquid. If the cat patient is hospitalized, metronidazole can be given as an injection. Some oral formulations are flavored to help improve the taste, but many cats simply dislike oral medications. It can help to reward them with their favorite food or treat after giving the medication.

Overall, depending on the underlying cause, metronidazole can be a safe and important treatment to help resolve diarrhea in cats.

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