By Rania Gollakner, BS, DVM, MPH

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’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions 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. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. Measure liquid forms carefully.

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?

Give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effects include constipation, bloat, and sleepiness. Dogs with the MDR1 genetic mutation (see risk factors) can become very sedated.

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. Do not use in pets with diarrhea due to an infection or a toxin. Use loperamide cautiously in pets with low thyroid levels, head injuries, liver disease, kidney disease, respiratory disease, Addison’s disease, that are very old, or are debilitated. Loperamide should also be used cautiously in pregnant or nursing pets. Use in cats is controversial and loperamide should be used with extreme caution, if at all.

Do not use in dogs that are positive for the MDR1 gene. Some breeds of dogs (e.g., Collies, Sheepdogs, and Collie- or Sheepdog-cross breeds) are more sensitive to loperamide than others. This is typically due to a specific genetic mutation (MDR1) that makes them less able to tolerate high doses of loperamide. Your veterinarian will advise you on the safety of loperamide use in your dog.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with loperamide: amiodarone, carvedilol, CYP2B11/CYP2D15/CYP3A12 substrates, erythromycin, gemfibrozil, ketoconazole, itraconazole, quinidine, tamoxifen, trimethoprim and sulfamethoxazole, or verapamil.

Loperamide may also interact with amylase and lipase blood values by increasing them 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.

Is there any monitoring that needs to be done with this medication?

Your pet’s hydration status and electrolyte levels should be monitored. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet for sedation level and for serious side effects at home.

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.

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.

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