Loperamide

What is loperamide?

Loperamide (brand names: Imodium®, Anti-Diarrheal®, Diamode®) is an antidiarrheal used to treat the signs of diarrhea. It is available over the counter but should only be used as directed by your veterinarian.

Its use in dogs, rabbits, rodents, and small mammals to treat signs of diarrhea is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is loperamide given?

• Loperamide is given by mouth in the form of a tablet, capsule, or liquid.
• Measure liquid forms carefully.
• Loperamide can be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then wait the recommended time for the next dose, as prescribed by your veterinarian. Do not give the pet two doses at once.

Are there any potential side effects?

Loperamide may cause the following side effects:

• Constipation
• Bloat
• Sleepiness
• Sedation (in dogs with the MDR1 genetic mutation)

Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.  

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours.

Are there any risk factors for this medication?

DO NOT USE loperamide in:

• Pets that are allergic to it
• Pets that have diarrhea due to an infection or a toxin
• Dogs that have the MDR1 gene

USE WITH EXTREME CAUTION in:

• Cats (use in cats is controversial; use with extreme caution, if at all)

USE WITH CAUTION in:

• Pets that have low thyroid levels
• Pets that have head injuries
• Pets that have liver disease, kidney disease, respiratory disease, or Addison’s disease
• Pets that are very old or debilitated
• Pets that are pregnant or nursing

Some dog breeds are more sensitive than others to medications (e.g., collies, sheepdogs, and collie- or sheepdog-cross breeds). This sensitivity is typically due to a genetic mutation (MDR1/ABCB1) that makes them less able to tolerate high doses of certain medications. Do not use loperamide in these cases. Your veterinarian will advise you on the safety of loperamide use in your dog.

Are there any drug interactions I should be aware of?

Several medications should be used with caution when given with loperamide, including:

• CYP2B11/CYP2D15/CYP3A12 substrates
• Itraconazole
• Ketoconazole
• Sulfamethoxazole
• Trimethoprim

Loperamide may increase amylase and lipase blood values for up to 24 hours after dosing. Advise your veterinarian that your pet is taking loperamide before blood tests are taken.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your pet’s hydration status and electrolyte levels should be monitored.
• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store loperamide?

• Store this medication at room temperature, between 59°F and 77°F (15°C and 25°C), and protect from light.
• Keep the container out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.