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If you’ve never had to deal with dog diarrhea, you’re a fortunate pet owner. Like it or not, this is a common complaint in canines. While an extreme bout can be a sign of something serious, it’s not unusual for your dog to be temporarily unwell after eating something that doesn’t agree with them or when suffering from a mild tummy bug.

If your dog is prone to picking up things they shouldn’t, you might be tempted to grab some anti-diarrhea drugs from your medicine cabinet to stem the flow. But is this the best strategy?

We asked a veterinarian about Imodium® (loperamide) for dogs, why you should use the drug cautiously or not at all, and the safer alternatives.

What Is Imodium and When Is It Given to Dogs?

Imodium is the brand name for a low-cost, over-the-counter antimotility drug with the active ingredient loperamide. Imodium is used to treat diarrhea in dogs the same way it’s used for humans.

Loperamide is a synthetic opioid that boosts small intestine muscle tone and slows digestive waste passing along the intestinal tract. This promotes better absorption of fluids, which equals less watery stools. It’s thought that loperamide might help tighten the anal sphincter, so it could also be helpful for fecal incontinence in dogs.

Pug pooping outdoors in tall grass.
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How Safe Is Imodium for Dogs?

When your dog is in diarrheal distress, and you’re struggling to get them outside quickly enough to prevent an accident, Imodium can seem like an attractive quick fix. However, there are many medical reasons why administering loperamide can be harmful—and even life-threatening—for dogs.

Dr. Deborah Mandell, VMD, is a Professor and Director of Emergency Service at Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania. She says that an owner should never give Imodium (or other drugs containing loperamide) without contacting their veterinarian first to ensure there aren’t risks.

Never Give Imodium to Dogs With the MDR1 Mutation

If you know your dog has the multidrug resistance 1 gene (MDR1 or ABCB1 mutation), never give them medication containing loperamide. Your vet will also not prescribe Imodium to dogs with this gene. Dr. Mandell says this is the biggest concern because it has significant central nervous system side effects. The drug can lead to neurological toxicity, putting your dog at risk of severe, life-threatening complications.

Herding breeds are at the highest risk of being affected by this gene mutation, but it can affect many dogs, including:

“Most owners are not going to know their dog’s MDR1 status,” Dr. Mandell says. By avoiding administering Imodium, it removes any uncertainty.

German Shepherd puppy laying down alert in the grass.
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Other Potential Risks of Imodium

Imodium isn’t right for all dogs. “Due to potential sedative effects and negative effects on the GI tract, loperamide shouldn’t be used in dogs with respiratory disease, liver disease, endocrine disease, head injury, neurologic disease, or if the dog is very sick,” Dr. Mandell says. “And it can make them more sick if the diarrhea is due to infectious or toxic causes.”

Examples of conditions where using loperamide for dogs could be problematic include Addison’s disease, hypothyroidism, parvovirus, and hydrocephalus. Other times when you shouldn’t use Imodium include on:

  • Pregnant or nursing bitches

  • Puppies under six weeks old

  • Toy breed dogs

  • Dogs with fever

  • Dogs with bloody diarrhea

Interaction with Other Drugs

Chinook puppy laying down outdoors.
Patti Richards

“Loperamide may also interact with medications the dog may be on,” Dr. Mandell says. Some drugs that Imodium is known to be a problem when used alongside include:

  • Antihistamines

  • Certain antibiotics (including erythromycin, trimethoprim, and sulfamethoxazole)

  • Certain antifungals (including ketoconazole and itraconazole)

  • Certain heart meds (including amiodarone, carvedilol, propranolol, quinidine, and verapamil)

  • Monoamine oxidase inhibitors such as L-Deprenyl (also known as Selegiline and sold as Eldepryl and Emsam) or meperidine (sold under the brand name Demerol)

  • Tranquilizers

Are There Safer Alternatives Than Imodium for Dogs With Diarrhea?

“Most cases of diarrhea respond to conservative therapy and don’t need Imodium,” Dr. Mandell says. “It is much safer to start by switching to a bland diet and adding probiotics,” she says.

Probiotics for dogs help safely restore a healthy intestinal microbial balance and a bland diet, such as a mix of plain boiled chicken and white rice, is gentle on the gastrointestinal tract. Feed small meals frequently throughout the day rather than one or two large ones.

“If this is not resolving the diarrhea, then it may be that the diarrhea is actually a sign of something more serious going on,” Dr. Mandell says. Contact your veterinarian for advice if things don’t settle after 48 hours. This is also important if other symptoms, such as vomiting, stomach pain, appetite loss, fever, or lethargy, accompany the diarrhea.

Chihuahua getting a check-up at the vet.
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Imodium for Dogs Side Effects

If your dog doesn’t have a known contraindication to loperamide, and you administer the correct dosage, they’ll rarely have problems. However, as with any drug, there can be side effects. “These include sedation—which can be significant—bloat, constipation, pancreatitis, and distended colon,” Dr. Mandell says. You shouldn’t use Imodium unless instructed to do so by your vet, and only in the dosage prescribed.
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