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What is Metronidazole (Flagyl) Toxicity?

Although there have been serious side effects reported in some dogs, if it is prescribed, then the veterinarian believes your dog will benefit from metronidazole. You should always talk to the veterinarian about any side effects or complications before administering them to your pet. The chance of metronidazole toxicity may be low, but it is possible that it could affect your dog in a bad way. There are serious implications with metronidazole, such as neurological injury and hepatotoxicity (liver damage).

Metronidazole, or Flagyl, is an antibiotic and antiprotozoal drug that is used in treating many kinds of infections such as diarrheal disorders, giardia, inflammatory bowel disease, and dental infections to name a few. Because it is able to pass through bone, it is often given for oral infections and is a commonly used drug for inflammatory disorders of the large intestine. However, this drug is not approved by the FDA for use in animals, so if your veterinarian prescribes it you should talk about this decision carefully.

Metronidazole (Flagyl) Toxicity Average Cost

From 569 quotes ranging from $200 - $1,000

Average Cost

$350

Symptoms of Metronidazole (Flagyl) Toxicity in Dogs

The symptoms of metronidazole toxicity may be immediate, could take several hours, or can even take 7-10 days to show up, depending on the dosage and the cause. Allergic reaction is usually immediate, but with an accidental overdose it may be several days before your dog starts to show any signs of complications.

  • Drooling
  • Gagging
  • Smacking lips
  • Pawing at the mouth
  • Cough
  • Sneezing
  • Runny nose
  • Extreme lethargy
  • Weakness
  • Nausea
  • Vomiting
  • Appetite loss
  • Fever
  • Chills
  • Hives
  • Dizziness
  • Confusion
  • Agitation
  • Sores inside the mouth or on the lips
  • Watery or bloody diarrhea
  • Loss of balance or coordination
  • Swelling of the face, lips, tongue, or throat
  • Inability to walk
  • Irregular heart rate
  • Difficulty breathing
  • Liver damage (yellowing of the eyes and skin, appetite loss, fever, diarrhea, fluid retention)
  • Seizures
  • Death

 Types

  • Overdose occurs when the wrong dose or a double dose is given or if your dog gets into the medication
  • Bad reaction can be from an allergic reaction or drug sensitivity
  • Drug interaction happens when you give your dog metronidazole with another drug that should not be mixed; some of those drugs are warfarin, coumarin, cimetidine, sedatives, phenobarbital, and phenytoin
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Causes of Metronidazole (Flagyl) Toxicity in Dogs

  • Accidental overdose
  • Allergy
  • Drug interaction
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Diagnosis of Metronidazole (Flagyl) Toxicity in Dogs

Try to bring your medical and shot records and be prepared to explain the reason for your visit in detail. Also, be sure to bring the metronidazole with you and tell the veterinarian if you have given any other medications besides the metronidazole. The veterinarian will need to perform a detailed physical examination, which includes height, weight, body temperature, reflexes, pupil reaction time, coat and skin condition, breath sounds, heart and respiratory rate, blood pressure, and oxygen level. Some important tests for verifying metronidazole toxicity are a spinal tap and an MRI. Your dog will be anesthetized for both procedures for safety. The spinal tap is done by inserting a thin needle into the spinal cord at the back of the neck or lower back and collecting spinal fluid into a tube to be analyzed. The spinal tap will likely show increased protein.

An MRI (magnetic resonance imaging) will be done to check the brain functioning, which may find hemorrhaging and degeneration of the cerebellum. Other tests are usually found to be normal, but the veterinarian will want to do a blood count and serum analysis to check for underlying illness or side effects. In addition, radiographs (x-rays), CT scan, and an ultrasound may be done for further inspection.

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Treatment of Metronidazole (Flagyl) Toxicity in Dogs

Treating metronidazole toxicity is done by stopping the medication and treating the symptoms as they occur.

Fluid Therapy

Your dog should already be receiving intravenous (IV) fluids from the earlier procedure. The veterinarian will likely continue the fluids and add nutrients and electrolytes as needed. This will keep your pet from getting dehydrated and flush the kidneys as well.

Medication

The medications your dog is given depends on the symptoms and test results, but will likely administer diazepam right away. This drug is able to alleviate vestibular dysfunction in animals and shortens the recovery time. However, the average length of recovery time is 12-16 days and may be as long as three weeks.

Hospitalization

The veterinarian will likely suggest your dog be hospitalized for at least 24 hours for observation and supplemental treatment. The length of your dog’s stay depends on the severity of the symptoms and how well your pet responds to treatment.

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Recovery of Metronidazole (Flagyl) Toxicity in Dogs

Recovery from metronidazole toxicity is a long process and depends on the amount of time your dog was on the medication and how much was given or accidentally ingested. Usually, all of the side effects can be reversed and your dog should have no lasting complications as long as your pet received treatment from a veterinary professional. Be sure to follow the veterinarian’s instructions and return for your pet’s follow up appointment for evaluation.

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Metronidazole (Flagyl) Toxicity Average Cost

From 569 quotes ranging from $200 - $1,000

Average Cost

$350

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Metronidazole (Flagyl) Toxicity Questions and Advice from Veterinary Professionals

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Golden Retriever

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Nine Weeks

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Unknown severity

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Diarrhea

My dog was on flagyl for diarrhea for 5 days and immediately when it was stopped the diarrhea came back. Does she need a longer course? Or a different treatment? The diarrhea is green and mucous and almost liquid

Aug. 5, 2020

Owner

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Jessica N. DVM

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Hello- Thank you for your question. I'm sorry your pup is experiencing diarrhea. If you haven't already I would recommend having a stool sample checked and having you puppy dewormed as well. I would also recommend adding in a probiotic such as fortiflora or proviable for your pet and consider a gastrointestinal diet (Hill's i/D) for a few weeks to see if that helps. You may need another course of metronidazole as well. I would give your veterinarian a call to follow up on the continued diarrhea. Unfortunately it is not uncommon for puppies to experience diarrhea, and sometimes it can take some patience and trial and error to get to the root cause and get it cleared up.

Aug. 5, 2020

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Pitmix

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Seven Years

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Unknown severity

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Unknown severity

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Tarry Stool

My dog has been on metronidazole since Wednesday definitely doing much better. She had no worms or colitis. But she's still having small loose stools. Today would be day 4. Is this normal with this medication? I also started flora flora yesterday.

Aug. 3, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question. It can take a little bit of time for metronidazole to start to take effect and clear up diarrhea, depending on the cause. If things are generally getting better for your dog, I think that is the right direction. If you are not sure that things are getting better, it would be best to call your veterinarian, let them know that you are not sure, and see what their recommendations are. I hope that all goes well for your dog.

Aug. 3, 2020

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Pomeranian

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Eight Years

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Unknown severity

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Unknown severity

Has Symptoms

Licking Lips Frequently And Hiccups

she just started this yesterday taking 1/2 pill twice a day for diarrhea. Fluffy is 10 pds also she was on flaygl on July 10th then she was taking only 1/4 pill 2 times per day

Aug. 2, 2020

Owner

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Dr. Sara O. DVM

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Hello, this medication has a wide range that can be used. She may have also gained weight. For the dosage, I use she would fall right between 1/4 and 1/2. In more severe cases I will give the 1/2 and less severe the lower amount. If you are worried about the dosage, talk to your vet to make sure that you have the correct dosage of medication.

Aug. 2, 2020

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Mutt

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Three Years

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Unknown severity

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Loose Bowel Movements

How long does it take to get out of their system after they took the last pill. Can it make them nauseous

July 26, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question. That medication does not tend to cause nausea, and if your veterinarian gave it to your dog for diarrhea, the diarrhea should be resolved by the time you finish the medication. If it is not getting better, it would be best to have a recheck with your veterinarian, as there may be something else going on. I hope that all goes well for your dog!

July 26, 2020

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Yorkie

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Eight Years

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Panting, Won'T Settle

Took my dog to the emergency vet two days ago with bloody diarrhea. Vet prescribed metronidazole and a probiotic. Today she's panting and can't seem to settle.

July 21, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question. She may still be uncomfortable from her GI upset. If things are getting better with her metronidazole and probiotic, then she may just need to some time to adjust and feel better. If she is not getting better with the metronidazole and the probiotic, and she is still having problems. It would be best to have a recheck with your veterinarian, and see what is going on. I hope that all goes well for her.

July 21, 2020

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Mozzie

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toy poodle

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1 Year

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Moderate severity

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Moderate severity

Has Symptoms

Lethargy
Sneezing
Wheezing

My 1 yr old 9 lb toy poodle was acting skittish and very lethargic/depressed. Some diarrhea and vomiting. Vet said he found bacteria in her feces so he prescribed metronidazole. After reading all these comments I'm terrified. She's had 2 x 50 mg doses so far over 12 hrs and she's started sneezing and wheezing. Her lethargy is getting worse. My vet keeps shrugging my concerns off, what should I do?

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Ivy

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Labrador Retriever

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8 Years

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Serious severity

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Serious severity

Has Symptoms

Diarrhea
Increased Thirst
Drowsiness
Jaundice
Incontinence
Sneezing
Increased Urination
Vomitting
Tremors
Runny Nose
Mucus
Lack Of Appetite
Runny Eyes

Please stay away from this medication for your dog. My dog has mucus in her poop over a month ago. It wasn’t diarrhea at that time, just a casing of mucus. I took her to the vet the next day for routine shots and a check up. I mentioned that she had a weird poop. I was told it was Colitis and was given Metrondiazle for 4 days 500mg. Her poop didn’t get better, it progressed over those 4 days to mucus and yellow diarrhea. On the 4th day her hair fell out on her back end, And she was sneezing a lot- like 8-10 times in a few minutes. She had a runny nose and runny eyes.so we rushed her back to the vet. I was told it was “ Unlikely “ the medication caused this and to keep an eye on it to see if it spreads to other parts of her body. It did. Her poop became better off the drug, still a weird color, but she stopped eating. I switched her dog food, and started adding probiotics. She started to have a small amount blood and soft stool, not fully diarrhea I noticed she stopped being as active as she was prior. We went to the vet again. This time, they did xrays, full bloodwork, a skin scraping etc. I was given Metrondiazle again for 10 days this time, 500mg. The same night I ended up rushing her to the ER vet. Her poop became fully bloody, and dark. They did a full GI profile and found nothing abnormal. I was given a prescription food for food intolerance ( Prescription diet Z/d. )and told to cut the metronidazole in half and give her half in the AM and half at night. She was eating that food fine, it seemed to be helping. It took a few days before she had 4 days of normal stool. I was called about her blood work by my normal vet, and they said everything was normal. Thyroid, liver etc. xrays were normal too. Then my dog stopped eating the prescription food, and became increasingly thirsty, she was drinking more, and urinating more. I rushed her to my normal vet again. The vet didn’t even touch her. He told me “ she’s doing it for attention and acting out because she doesn’t like the bland food” he also said we didn’t need to do bloodwork because she just had bloodwork done 10 days ago and it was normal so there’s no reason to believe it was anything serious. He told me to withhold her water and only give her 8 cups a day. My dog was falling asleep in her empty water bowl, and just wanted to drink constantly. She was having tremors through her body. I rushed Her to the ER vet, xrays were done again and showed an enlarged spleen. She was rushed into an ultrasound where all her organs looked normal, just enlarged spleen. They did blood work, urinalysis and it came back that she was in liver failure. She was admitted to the ER for 5 days. I was able to take her home, her eyes were yellow, she was sleeping all the time. She was put on densyol, amoxicillin, vitamin K1, vitamin E, ondestron, omzepropal, liver diet and guess what else? Metronidazole. I didnt want to give it to her, and I shouldve put my foot down more. My dog has lost all control of her bowls and urine. She urinates and defecates while sleeping. Can’t go normally anymore. I called the ER vet and stated that I believe this drug caused the Hepotoxicity in my dog, and is still making her sick. They told me it’s really rare and highly unlikely and if I wanted to stop the metronidazole I would have to find another vet and they could no longer help me. It was rude, and made me feel like I was crazy. This drug is dangerous. Vets need to stop stating fatal adverse reactions are rare. They do happen, and they happen often. This drug did this to my dog. All it took was 10 days, a simple case of diarrhea turned into a critical case and me possibly loosing my best friend. I stopped giving her this drug and in a day she has regained some control of her bowels and urine. She is drinking less and the yellowing of her eyes has gotten better. I have hope that she can be saved, and I dont want to imagine my life without her. I still have her on the other liver medications, but I refused to give this drug to her. Probiotics can help with simple diarrhea, and so can Firm Up for dogs. Please try those first before you give this drug to your dog. I hope everyone who lost their babies to this is okay, and has found peace with it.

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Baby Jane

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Dachshund

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5 Years

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Moderate severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

Has Symptoms

Lethargy
Sneezing
Rash

Hi, My dog was recently prescribed this as she has severe liver problems. She is also on Ursodiol, Denamarin, and Lactualose. She had actually been showing no symptoms of anything but I knew she had liver damage and so she has been on the Denamarin and Ursolidol for a long time. I'm very concerned as it's been over a week and she seemed fine until yesterday morning when she started sneezing. She goes into occasional sneezing fits and I noticed a red rash on her belly (they had shaved it for the ultrasound she had so it's clear to see red splotches. Yesterday, she did not want to walk (and she LOVES walks) and just sat down in the driveway. today she walked fine but kept sneezing. I checked the pollen in the air and it's mid-range. We use unscented detergents and she's never reacted to any cleaning products we use and after researching her new meds I found this. Could it be a toxic reaction? She is eating fine, seems her usual happy self except for the sneezing, squinty eyes, and rash. I think I will stop giving this to her for now until I can do more research. Is stopping it abruptly a bad idea too though?

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Fifi

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toy poodle

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14 Years

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Critical severity

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Critical severity

Has Symptoms

Diarr

My beloved toy poodle Fifi passed away unexpectedly after her dose of Metronidazole. Fifi had diarrhea and I took her to the Vet. She had lots of test and all was fine including her heart murmur. Except for the diarrhea she was doing great and had a follow up appointment with the vet as well as an appointment to be groomed. Fifi was my life being a widow and living alone. Fifi was a senior dog but ran around the house and yard like a puppy. The last thing I expected five hours after her vet appointment and taking Metronidazole she would pass away in my arms. I regret I did not do my "homework" about Metrondazole or I would never have given it to her. My heart broke as I read all the comments in this site. There is no time limit for grief and I miss my adorable Fifi so much.

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Fifi

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toy poodle

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14 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Critical severity

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Critical severity

Has Symptoms

Dog Died

I shared my experience and saw it four minutes ago and now deleted.....interesting! Wonder why? It was so hard for me to express my feelings and now deleted! Maybe I will get an explanation why my story of using Metronidazole has been deleted. When my tears stop I will submit it again and hopefully will not be deleted.

Metronidazole (Flagyl) Toxicity Average Cost

From 569 quotes ranging from $200 - $1,000

Average Cost

$350

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