Diarrhea in dogs may be treated with metronidazole (also called Flagyl). However, veterinarians have begun to treat dog diarrhea with this antibiotic as a knee-jerk reaction based on historical practices and theories rather than scientific data.
In recent years, research suggests metronidazole is not as effective as previously thought for certain gastrointestinal disorders. Furthermore, metronidazole can have long-term negative effects on your dog’s microbiome, in addition to its troubling side effects.
Metronidazole has become the most commonly used antibiotic for dog diarrhea in general since it is effective for certain conditions that cause diarrhea (such as C. diff). Unfortunately, metronidazole may be the wrong choice in too many cases. According to several studies, metronidazole does not alleviate the symptoms of inflammatory bowel disease (IBD) or acute diarrhea in dogs.
What is the best treatment for your dog’s diarrhea? Is metronidazole the right choice? Does it work as well as it should? Let’s talk. We’ll discuss some appropriate and inappropriate uses of this drug, and offer some information that contradicts older assumptions. We’ll also offer some questions to ask your veterinarian if he or she suggests using metronidazole.
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How Is Metronidazole Used in Dogs?
In addition to being an antibiotic, metronidazole works as an antiprotozoal treatment against certain parasites and bacterial infections.
Dog diarrhea is often treated with this drug, which is also known by the brand name Flagyl. Infections in the central nervous system can be treated with metronidazole, which kills anaerobic bacteria (bacteria that do not need oxygen to survive).
The following conditions can be treated with metronidazole in dogs: Inflammatory bowel disease (IBD), Diarrhea, Oral and dental infections, Giardia, Sepsis (full-body inflammatory response to infection), Tear staining (medial canthus syndrome).
Metronidazole (Flagyl) Toxicity: What is it?
Metronidazole has been reported to cause serious side effects in some dogs, but if prescribed by a veterinarian, your dog is likely to benefit. Any side effects or complications should always be discussed with the veterinarian before administering them to your pet.
The possibility of metronidazole toxicity is low, but your dog may suffer adverse effects. With metronidazole, there are serious consequences such as neurological damage and hepatotoxicity (liver damage).
A medication called Flagyl, or metronidazole is used to treat many types of bacterial and fungal infections, including diarrhea, giardia, and inflammatory bowel disease, to name a few.
In addition to treating oral infections, it is also used to treat inflammatory disorders of the large intestine due to its ability to pass through bone. If your veterinarian prescribes this drug, you should discuss this carefully with him or her since it is not approved by the FDA for use in animals.
Is Metronidazole harmful to dogs?
The central nervous system may be adversely affected by metronidazole. It is known as metronidazole neurotoxicity when this happens. In dogs, this can result in seizures, comas, and death.
Pet owners have become more aware of metronidazole toxicity in the past few years. Dogs and other animals may die from metronidazole, but most people are unaware of this.
Dogs with metronidazole poisoning commonly display depression, lethargy, stumbling, vomiting, and diarrhea.
Consult your veterinarian immediately if you suspect your dog has ingested a potentially toxic substance.
The death of their dog resulted from ingesting metronidazole capsules prescribed by their veterinarian after a family in South Carolina experienced this firsthand. Their dog began having seizures shortly after recovering from a stomach infection. When her condition worsened several days later, she was taken back to the vet.”
My dog had GI problems a few years ago. She lost weight and started vomiting after stopping eating and being put on a diet of canned food. Metronidazole, an antibiotic, was prescribed by my vet. She should be fine in a few days, I thought after giving her Metronidazole. I received a call from my husband that night telling me that our dog had died.
At the time of my vet’s visit, I didn’t know anything about Metronidazole. The vet bills were enormous, and grieving for our lost pet was a very emotional experience. I’ve learned much more since then – and how dangerous it can be if your pets aren’t taking their medication properly.”
My dogs became sick after taking this drug. It will never be purchased again. My dog had diarrhea for days after taking it the first time. They got better when I stopped giving it to them. I then had to use it again because they became infected again. I had to use it again. The dogs suffered from diarrhea for days on end. I wouldn’t recommend it.
Is Metronidazole Right for You?
Since the 1950s, metronidazole has been an effective antibiotic and antiprotozoal medication. Anaerobic infections (bacteria that do not need oxygen to thrive) are treated with it in both human and veterinary medicine. Unlike other antibiotics (such as clindamycin) that attack anaerobic bacteria, metronidazole kills the bacteria instead of simply halting their growth.
For instance, metronidazole is effective against Bacteroides fragilis, a bacterium normally found in the gut and mouth microbiome, but can also cause wound infections, abscesses, and chest infections (usually linked to pneumonia), and liver infections. As metronidazole can penetrate bone, it’s useful for treating mouth and jaw infections, as well as gallbladder infections.
In addition to Clostridium difficile (C. diff), metronidazole is also effective against Clostridioides. This group of bacteria causes diarrhea in humans and animals.
Cats and dogs may both be treated with metronidazole if the gastritis is caused by Helicobacter bacteria in the stomach (such as H. pylori). Also useful against sepsis, which damages the tissues and organs due to uncontrolled immune response.
To cover a wide range of bacteria, metronidazole is usually combined with other antibiotics when used for Helicobacter treatment and sepsis.
Dogs with diarrhea caused by Giardia, a protozoan parasite, were treated with metronidazole in the past. Metronidazole, however, has developed resistance to that organism over time, so it is no longer effective alone against Giardia. Toward the end of this article, we will discuss antimicrobial resistance in more detail.
Is metronidazole safe for dogs?
A properly used antibiotic, metronidazole is generally safe when used to treat infections. Besides treating a variety of conditions, metronidazole is also used to treat intestinal parasites, which makes giving it to your pet even more tempting.
It’s important to keep in mind, though: dogs and metronidazole aren’t always friends. If your dog is given too much of the drug or if it’s used in some situations, the drug may be downright dangerous.
Metronidazole for dogs: common dosage
As a pill or liquid suspension, metronidazole can be taken orally. Veterinary offices can administer the drug by injection. It may be difficult to administer liquids flavored with this drug due to its bitter taste. To reduce the chances of stomach upset, it is best to take metronidazole with food.
Metronidazole is typically given two to three times a day in dosages of 10 to 30 milligrams per kilogram. This medication needs to be taken by most dogs for at least five to seven days.
Some dogs may need treatment for a month or longer, depending on their condition. Based on your dog’s weight and the condition being treated, your veterinarian will determine the appropriate dosage and treatment course.
Metronidazole: Use with Caution: A New Study
Most antibiotics kill both the bad bacteria they’re supposed to kill, as well as the good bacteria the body needs to function. Due to this, important members of the gut microbiome can disappear, resulting in bacterial imbalances that are harmful.
In a new study published in the Journal of Veterinary Internal Medicine, researchers have demonstrated that metronidazole has dramatic effects on the gut microbiome of dogs in particular.
Researchers found that metronidazole treatment led to significant changes in the gut microbiome in healthy dogs, including the reduction of beneficial bacteria like Fusobacteria-one of the most prevalent groups of bacteria in dogs (and cats) gut microbiomes-and reductions in overall diversity (the number of bacterial species present).
It’s also worth mentioning that these effects were not just temporary: four weeks after these dogs had stopped taking metronidazole, these microbiome changes still hadn’t completely resolved, meaning that these dogs still didn’t have enough of some of the bacteria that are essential for healthy gut function.
Veterinarians should use metronidazole with caution in dogs that already have imbalanced gut microbiomes, according to the study’s authors.
Dr. Karen Becker and Rodney Habib, integrative veterinarians and pet wellness educators, highlighted this study using a Facebook Live event that gained a lot of attention among pet parents.
In this podcast, Becker and Habib explore the potential overuse of metronidazole in cats and dogs with diarrhea, suggest several alternative treatments for GI problems, and emphasize the importance of testing your pet’s gut health after treatment with metronidazole or another antibiotic.
Can Dogs Overdose on Metronidazole?
Getting too much metronidazole can lead to an overdose in dogs. A small amount of extra accidental dosage can be deadly. When used long-term, metronidazole can cause toxicity even at recommended doses. Metronidazole generally has a toxic dose of around 60 milligrams per kilogram. That’s why it’s so important to give the medication exactly as your veterinarian recommends.
An overdose of metronidazole can cause liver and nervous system damage. These are some of the serious side effects dogs can experience.
You should contact a veterinarian immediately if your dog consumes too much of this medication. You can contact your local veterinarian or a pet emergency center, or you can contact a poison control service such as ASPCA Animal Poison Control at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661.
You may be advised to induce vomiting if the overdose occurred recently. You should visit a veterinarian for follow-up treatment.
Can My Dog Still Have Diarrhea After Taking Metronidazole?
After finishing the course of metronidazole, if your dog still has diarrhea, contact your veterinarian. Even better, consult your veterinarian if diarrhea doesn’t improve (or worsens) during metronidazole treatment. A longer course of medication or a different treatment may be needed for your dog.
A dog’s gut contains beneficial bacteria that aid in digestion and immune function. The gut microbiome can be adversely affected by all antibiotics, but metronidazole may have the greatest impact. Metronidazole may still cause diarrhea in some dogs.
If this is a concern for you and your dog, talk to your veterinarian about your options. Probiotics can benefit your dog’s digestive system by replacing the beneficial bacteria.
Does My Dog Need Antibiotics?
The answer may be no in many cases of dog diarrhea. Antibiotics may be necessary for some conditions, such as life-threatening bacterial infections, but supportive care may suffice for others.
It is common practice to give dogs with hemorrhagic gastroenteritis (bloody diarrhea) antibiotics, but according to veterinary consensus guidelines, antibiotics are appropriate only when sepsis is present. According to recent research, even hemorrhagic gastroenteritis responds as well to supportive care as it does to antibiotics so long as sepsis is not involved.
Metronidazole is actually known to make diarrhea worse, not only by reducing populations of “good” anaerobic bacteria, but also by altering mucus in the intestines.
Is metronidazole harmful to my dog?
It’s a medication known to cause side effects, though it’s not clear exactly what they are. When dogs with pre-existing conditions like kidney or liver problems take metronidazole, they may suffer liver damage or even die.
Drowsiness, nausea, and vomiting are among the most frequent side effects. Stomach cramps, diarrhea, and constipation are less common side effects. Additionally, rashes or itching of the skin may occur, as well as visual changes, mood changes, shortness of breath, dizziness, muscle pain or weakness, difficulty breathing or swallowing, swelling of the face, and changes in urination.
If you notice any of these symptoms after taking metronidazole or any other medication or supplement, contact your veterinarian right away.
Metronidazole (Flagyl) toxicity in dogs: diagnosis and treatment
Bring your medical records and shot records as well as a detailed explanation of why you’re visiting. You should also bring the metronidazole with you and tell the vet if you gave the pet any other medications.
Veterinarians will need to conduct a thorough physical examination, which will include weight, body temperature, reflexes, pupil response time, coat and skin condition, breath sounds, heart rate, blood pressure, and oxygen saturation.
Blood tests and urine analysis are important tests to verify metronidazole toxicity. Because neurological signs are often present, we may also advise a spinal tap and MRI or CT scan. In order to ensure your dog’s safety, these procedures will be performed under anesthesia.
During a spinal tap, a thin needle is inserted into the spinal cord at the back of the neck or in the lower back, and the spinal fluid is collected into a tube for analysis. It is likely that an increase in protein will be detected.
In order to check the brain function, an MRI (magnetic resonance imaging) might reveal hemorrhage and cerebellar degeneration. However, a blood count and serum analysis will be done by a veterinarian in order to check for underlying illnesses or side effects. For further examination, radiographs (x-rays), CT scans, and ultrasounds may be performed.
After a course of antibiotics, test your dog’s gut health
When you finish a course of metronidazole or any other antibiotic, you should determine whether your dog’s unique microbiome has been altered, especially if there is a bacterial imbalance (dysbiosis).
You can discover which bacteria populations are present in the gut of your dog, which beneficial strains might not be present, and what specific steps you can take to promote the health of your dog by testing the gut.
A detailed report on your dog’s gut microbiome is included in our Gut Health Tests, along with dietary, lifestyle, and supplement recommendations.
Adding more protein to your dog’s diet may help, for example, if you discover your dog’s feces show an absence of Fusobacteria bacteria (which metronidazole is known to wipe out), since Fusobacteria grow best in protein-rich environments.
If the antibiotics have destroyed too many of the bacteria required for a healthy gut in your dog, our Gut Restore supplements can replenish this diversity.
Misuse of Metronidazole
Metronidazole is commonly used by veterinarians to treat diarrhea in general because research has found it effective against certain causes of diarrhea in dogs. The problem with metronidazole is that little scientific evidence exists that it can help some of the conditions it’s used for.
Despite this, metronidazole is the antimicrobial agent prescribed most commonly for dogs with acute diarrhea, even without strong scientific evidence that it works. Research has found that metronidazole is the wrong choice for three common conditions.
Giardia Infection – Cats and dogs have both been treated with metronidazole for infections caused by the protozoan parasites Giardia and Trichomonas in the past, which cause diarrhea. As a result, metronidazole has become unavailable as a treatment for both of these protozoal infections due to their resistance to this medication.
Inflammatory Bowel Disease (IBD) – Since metronidazole is beneficial in treating Crohn’s disease in humans, it is often used to treat diarrhea in dogs with inflammatory bowel disease (IBD) and other chronic diseases of the intestines, usually in conjunction with prednisone. Researchers determined in 2010 that metronidazole does not offer any additional benefit in this scenario: it does not outperform prednisone alone for treating IBD.
Acute Diarrhea – Because it has historically been effective against diarrhea-causing agents such as Giardia and C. difficile, veterinarians are increasingly using metronidazole to treat diarrhea caused by other causes. The evidence, however, shows that it does little good in treating acute nonspecific diarrhea (diarrhea with no clear cause) in cats or dogs – the vast majority of cases of diarrhea.
There is some evidence that metronidazole reduces the duration of acute diarrhea in the veterinary world. In dogs, this reduction in lifespan only lasted a few days, according to a study. Dog diarrhea generally resolves in a few days, regardless of the treatment, as the authors noted.
A study that compared metronidazole and placebo for treating acute diarrhea in dogs found no significant difference. Metronidazole use for such cases “should be discouraged until evidence-based data demonstrate a difference in treatment outcome,” the researchers concluded.
Human and animal health have been profoundly affected by antimicrobial therapies, including antibiotics. Until Alexander Fleming discovered in 1928 that penicillin inhibited the growth of bacteria, there was no treatment for infections like pneumonia, gonorrhea, and rheumatic fever. Without the availability of antimicrobial therapies, many surgical procedures and chemotherapies today would not be possible.
Antimicrobial Stewardship – However, as he himself warned, a high rate of antimicrobial use can result in antimicrobial resistance, not just in the bacteria targeted but also in other, related microorganisms. Antibiotics continue to be rendered ineffective in the modern world as dangerous bacteria become resistant to them.
The use of antibiotics must be done judiciously in order to prevent antibiotic resistance. This includes diagnosing the infection and making sure the antibiotic prescribed against that infection has been proven effective. Antimicrobial stewardship reduces the spread of latent infections caused by multidrug-resistant microbes, improves patient outcomes, and reduces resistance to antimicrobial drugs.
Microbiome Disruption – It is also important to consider that antimicrobials have a tendency to disrupt the gut microbiome by causing imbalances (dysbiosis) among resident bacteria. It has also become increasingly problematic to use antimicrobials on animals with already imbalanced gut microbiomes, such as dogs with irritable bowel syndrome and other chronic gastrointestinal disorders.
Because of these risks, antibiotics should be considered as a last resort. There have been alternative approaches to IBD and other causes of diarrhea in dogs, including the use of probiotics and fecal microbiota transplantation (FMT). FMT works better than metronidazole in dogs with acute diarrhea, a study published in Frontiers in Veterinary Science concluded in 2020. FMT helps to restore gut health, while metronidazole “has a negative impact” on the microbiome.
Also Read: Vetmedin killed my dog – How To Handle It?
The treatment of dog toxicity from metronidazole (Flagyl)
In the event of metronidazole toxicity, the medication should be stopped and the symptoms treated.
Fluid Therapy – You already administered intravenous fluids to your dog during the earlier procedure. Fluids will likely be given again and nutrients and electrolytes added as necessary by the veterinarian. You will avoid dehydration for your pet, and the kidneys will be flushed as well.
Hospitalization – If your veterinarian recommends that your dog be hospitalized for observation and additional treatment, it will likely be for at least 24 hours. It depends on how severe the symptoms are and how well your dog responds to treatment and how long your dog stays at the hospital.
Medication – Your dog’s medication depends on both the symptoms and results of the test, but diazepam is likely to be administered right away. As a result of this drug, vestibular dysfunction in animals is alleviated and the recovery process is shortened. A patient’s recovery may take as long as three weeks, but averages 12-16 days.
Dogs recovered from Metronidazole (Flagyl) toxicity
There is a long recovery process for dogs with metronidazole toxicity, depending on how long they were given the medication and how much they accidentally ingested.
In most cases, all of the side effects can be reversed and your pet should not experience any lasting complications if your pet is treated by a veterinarian. Be sure to follow the veterinarian’s instructions and make an appointment to have your pet evaluated after the initial treatment.
Metronidazole toxicity can be extremely expensive to treat out of pocket. Fortunately, 90% of the expense is refunded by most pet insurance companies within 3 days of filing a claim. Do you need pet insurance? Find the right coverage for your pet by comparing pet insurance plans.
Metronidazole Side Effects: What Can You Expect?
Side effects are possible with most medications, so be sure to ask your veterinarian what to watch out for. Especially in cats, metronidazole has an extremely bitter taste and often results in excessive salivation, drooling, gagging, or profuse frothing at the mouth.
The bitter taste may also cause nausea and loss of appetite (anorexia) in cats and dogs taking metronidazole. As a result, pets taking metronidazole may eat less than normal or refuse meals altogether. It is also fairly common to experience vomiting and diarrhea while taking this medication.
Lethargy, weakness, liver damage, and central nervous system disorders are more serious but less common adverse effects of metronidazole in pets. An abnormal eye movement, head tilt, fall, stumbling, or knuckling can be signs of toxicity of the nervous system.
Birth defects have been reported in some cases. There have been reports of dogs having low blood counts as an idiosyncratic reaction. DNA damage has been found to occur in lymphocytes (white blood cells) caused by metronidazole in cats.
Are there any conditions that may make my dog more likely to react badly to metronidazole?
A dog that has previously experienced an allergic reaction to metronidazole should not be treated with it. You shouldn’t give metronidazole to a pregnant dog.
Metronidazole should be used with caution and at a very low dose if your dog has liver disease. In addition, animals with compromised nervous systems should also be used cautiously.
Can I combine metronidazole with any supplements to improve my dog’s outcome?
Some probiotics may aid in supporting better outcomes and reducing side effects. A combination of probiotics and metronidazole improved overall results in a study of shelter dogs with diarrhea compared to metronidazole alone.
One study found that dogs receiving metronidazole alone experienced worse appetite, intermittent vomiting, and weight loss compared with those receiving silymarin (a flavonoid derived from milk thistle seeds).
There are still many things you can do to help your dog feel better during and after a course of metronidazole or another antibiotic if you and your veterinarian decide such a course is warranted in your dog’s case.
Bacteria called Saccharomyces boulardii can reduce the risk of antibiotic-caused diarrhea in your pet. Many antibiotics cause diarrhea as a side effect. S. Bolardii is a probiotic that supports beneficial gut bacteria and inhibits pathogenic bacteria.
Gut Maintenance Plus (GMP) from AnimalBiome, which was developed specifically to treat antibiotic-induced diarrhea in cats and dogs, contains S. boulardii as well as Bio-Mos® and PreforPro® prebiotics.
Putting the drug in a food-grade capsule will protect your dog from the bitter taste of the drug and reduce the possibility of nausea if you and your veterinarian do decide on metronidazole.
What Are Metronidazole’s Alternatives?
Your veterinarian can recommend medication that treats specific aspects of your dog’s GI condition in place of an antibiotic.
Patients with chronic diarrhea may benefit from symptomatic treatments such as anti-nausea medications, proton pump inhibitors (to reduce acid production), motility inhibitors (to relieve cramps and the sense of urgency), bile acid sequestrants (to prevent bile acids from being reabsorbed by the body), and vitamin B12 (cobalamin).
There may be some changes to your dog’s gut microbiome from some of these approaches, but they will be much less drastic than the effects of metronidazole.
The fibers inulin and psyllium may help by feeding the bacteria in your dog’s gut and firming up her stool at the same time. Diarrhea indicates a disruption in the balance of these bacteria. S. boulardii is another supplement that may support healthy gut bacteria by resolving gut imbalances.
A dog’s gut microbiome may be out of balance if our Gut Restore supplements seed the gut with healthy bacteria specific to dogs.
Becker and Habib mentioned DiaGel, which contains the active ingredient carvacrol, during their Facebook Live event. As a phytonutrient (plant extract), carvacrol has antimicrobial properties and can be found in essential oils such as those oregano, thyme, and others. Carvacrol has been studied in other animals and in humans, but we haven’t found any studies that specifically describe its effect on diarrhea in cats and dogs.
In a study on C. diff infection in mice, carvacrol was found to be beneficial for the microbiome: it increased beneficial bacteria, including Firmicutes, and significantly reduced harmful bacteria, such as Proteobacteria.
According to other studies, carvacrol may also be effective against E.coli, Campylobacter, a few strains of Cryptosporidium and Salmonella, and even certain viruses. Future studies on this compound should specifically address its effects on cats and dogs.
Is it possible for a dog to recover from metronidazole toxicity?
It usually takes two to four weeks for most dogs affected by metronidazole toxicity to recover after drug withdrawal (although some may never fully recover).
Within 30 minutes of ingestion, dogs who become intoxicated with metronidazole usually experience vomiting and diarrhea. Metronidazole can cause adverse side effects depending on the amount consumed.
The recovery of dogs who vomit shortly after ingesting metronidazole may be possible, but dogs who have consumed higher doses of the drug may not be able to fully recover.
How many days should I give metronidazole to my dog?
It may only take a few days in some cases. It’s best to give medication for at least 10 days in most cases.
Metronidazole should be given to dogs for a 7-day course instead of the usual 14 days.
When giving metronidazole to your pet, you should consider the age and general health of the animal. It is best not to give the medication to puppies and kittens if they are very young or very old because the medication can be toxic to them. Before administering metronidazole to your dog, consult your vet if you have concerns about his health.
What is too much metronidazole for dogs?
For dogs, the toxicity threshold is 13 mg/lb/day, according to the Merck Veterinary Manual. When the dose exceeds that level, it is extremely toxic.
It is the dose that makes the poison. The idea that higher doses of metronidazole have a more powerful effect is a common misconception. It is actually the dosage that determines the extent of metronidazole’s toxicity.
At higher doses, toxicity and death are more likely. It is very unlikely that toxicity or death will occur at the lowest dose.
Metronidazole and food: should you take it together?
Taking it with food or without it depends on whether you have nausea, vomiting, or diarrhea, but if you do, it’s best to do so.
Also Read: Can Cerenia Cause Death in Dogs?
Reviews of metronidazole
Metronidazole reviewers say it is effective in treating dogs’ intestinal problems. The fast-acting nature and ability of metronidazole to decrease intestinal inflammation and eliminate the cause of infection were praised by reviewers.
Reviews say many dogs are able to eat Metronidazole pills with peanut butter or cheese, but some reviewers report difficulty getting their dogs to swallow the tablets whole.
Metronidazole has positive reviews when treating diarrhea in dogs, as it stops any stomach issues from occurring quickly. However, some reviewers state that this product caused horrible side effects to their dogs, including vomiting, lethargy, and nausea.
The bitter taste of metronidazole is accepted by most dogs when diluted with food. In the case of dogs who are sensitive to bitter tastes, flavored suspensions (liquids) of metronidazole are available as an alternative. If your dog won’t take his medication, ask your veterinarian about this formulation.
Final Thoughts On metronidazole killed my dog
Dogs have commonly prescribed metronidazole as an antibiotic. Anaerobic bacteria and protozoa are sensitive to it. Giardia, an organism that lives in the intestines, is especially susceptible to the effects of metronidazole
Using metronidazole should only be done when it is necessary and shouldn’t be abused. Metronidazole should not be administered to dogs that are pregnant or have liver or kidney disease. Some dogs can also have an unpleasant reaction to metronidazole.
The veterinarian may prescribe probiotics or recommend changes in your dog’s diet to ease their digestive issues in addition to metronidazole for dogs!