What Is Loperamide?
Loperamide (brand names: Imodium A-D, Difixn) is a medicine classified as an opioid antidiarrheal. It can be used in dogs and cats to treat loose stool and diarrhea that is not linked to an infection in the stomach or intestines. But its use in cats is controversial. It can also be given to dogs to prevent and treat diarrhea caused by cancerchemotherapy.
All uses for loperamide in pets are considered to be “off-label” or “extra-label.” This means that there may be evidence of safe and effective use, but it is technically not FDA-approved for pets. Use in cats to treat diarrhea should be done with extreme caution.
While there is a loperamide product (Difixn) specifically labeled for dogs, this product is not approved by the FDA. The human loperamide product (Imodium A-D) is FDA-approved for humans and can be used extra-label in dogs and cats. Loperamide products are available over the counter (OTC) in oral tablet, capsule, and liquid forms. Discuss loperamide use with your veterinarian so that you get the right amount for your pet. Contact your veterinary compounding pharmacy for alternative dosing options.
How Is Loperamide Used in Pets?
Loperamide is given by mouth up to three times a day as directed by your veterinarian. Though you may be using a loperamide product intended for humans, the dose for your pet will not be the same as on the product’s label. Your veterinarian will tell you how much to give.
Loperamide can be given with or without food. If your pet gets an upset stomach when the drug is given on an empty stomach, try giving it with a small amount of food or a treat. Some of the oral liquids must be shaken before use. Be sure to read the label. The oral liquid should be correctly measured using a dosing dropper or syringe before it’s given. Slowly put liquid medicines into a pet’s mouth so that they receive all of the dose.
Always follow your veterinarian’s directions for giving medicines to animals. Remember to tell your veterinarian about any medicines, vitamins, supplements, or herbal therapies that you are giving your pet. Talk to your veterinarian before stopping any pet medicines.
What Are the Benefits of Loperamide in Pets?
The benefits of loperamide include:
- It is available over the counter, so no prescription is needed.
- Loperamide is quick-acting and should start to work within an hour or two after the first dose.
What Follow-Up Is Required With Loperamide?
You and your veterinarian should monitor your pet for improvement of their condition, as well as for side effects of the medicine. A fecal (poop) examination may be needed if diarrhea continues or worsens while your pet is on loperamide. Your pet’s fluids and electrolytes (sodium, potassium, etc.) should be monitored if diarrhea is severe or if the diarrhea continues for more than a few days.
Does Loperamide Have Warnings or Side Effects in Pets?
Do not use loperamide in animals that are allergic to it. Do not use loperamide in pets with a blockage in the intestines. Do not use it for diarrhea that is caused by an infection, antibiotic use, or ingestion of a toxic substance. Do not use loperamide in dogs that have a specific gene mutation called MDR1.
Use loperamide with extreme caution in animals with breathing problems or brain conditions that cause tiredness or sedation. Use it with caution in animals that have low thyroid hormone or low blood pressure. Use it with caution in animals with liver problems or that are frail. The safety of loperamide in breeding, pregnant, and nursing animals has not been established, so caution is advised.
Side effects in dogs are usually related to the gastrointestinal system (stomach and intestines) and may include:
- Increased drooling
- Constipation
- Bloating
- Sedation or tiredness
Side effects in cats are less well studied but are likely similar to those in dogs. And loperamide can cause excitation and aggression in cats.
If loperamide gives your pet side effects, stop the medicine and contact your veterinarian. Your veterinarian will discuss treatment options depending on the side effects and may recommend switching to a different medicine.
If you suspect that your pet is having a serious side effect or may have been overdosed, call your veterinary clinic right away. If it is outside of regular office hours, you may contact a local emergency veterinary hospital or an animal poison control center. Note that fees may apply for emergency consultation.
You can reach the ASPCA Animal Poison Control Center at 888-426-4435 or the Pet Poison Helpline at 855-764-7661.
Does Loperamide Interact With Other Medicines (Drug Interactions)?
Using multiple medicines can sometimes change how your pet’s medicines work or increase your pet’s risk of serious side effects. Always tell your veterinarian about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements that your pet is using.
In particular, make sure that you discuss if your pet is using any of the following before using loperamide:
Medicines that are metabolized by cytochrome P-450 (CYP). Animals have many ways to metabolize (inactivate) medicines in the body. One way is through a group of enzymes called CYP. Loperamide can decrease the effects of certain CYP enzymes, specifically CYP-2B11, CYP-2D15, and CYP-3A12. Medicines that are normally inactivated by these CYP enzymes may not be inactivated as quickly. This can increase the risk of side effects from those medicines. Talk with your veterinarian to ensure they know all medicines that your pet is taking.
Medicines that are removed by P-glycoprotein (Pgp). Animals have many ways to remove medicines from the body. One way is through a transporter called Pgp. Loperamide can decrease the effects of Pgp, so medicines that are normally removed by Pgp may not be removed as quickly. This can increase the risk of side effects from those medicines. Talk with your veterinarian to ensure they know all medicines that your pet is taking.
Medicines that prolong the QT interval. Certain medicines can cause an abnormal heart rhythm called QT prolongation. Taking these medicines with loperamide can increase this risk, which can be serious. Talk with your veterinarian to ensure they know all medicines that your pet is taking.
This may not be a complete list of medicines that can interact with loperamide. Always check with your veterinarian.
Are There Safety Concerns for Pet Owners?
- Keep loperamide out of the reach of children.
- Wash your hands after giving loperamide to your pet.
- Do not handle loperamide if you are allergic to it.
What if My Pet Takes Too Much Medicine or Has an Overdose? What if I Miss a Dose of Medicine?
Too much loperamide can be a very serious problem. Overdose of loperamide in humans has caused death. If you suspect your pet has taken more loperamide than intended, call your veterinarian or veterinary emergency clinic right away.
Missed doses are not usually a concern with loperamide, since it is usually just given as needed. If you miss a scheduled dose, give the dose when you remember, then start on a new schedule from that time. Do not double the dose of the medicine.
How Do I Store Loperamide?
Loperamide should be protected from light and kept at room temperature.
