The usual dosage of Imodium for dogs is 0.05 to 0.1 milligram per pound every eight hours for one to two days, according to Pet Education. Imodium is a brand of narcotic anti-diarrheal medication used in humans.
Imodium works by slowing down the movement of food through the intestinal system and reduces toxic secretions that cause diarrhea symptoms, notes Vet Info. Some vets recommend Imodium to treat dogs with diarrhea resulting from inflammatory bowel disease. Because it slows down the digestive system, it is important not to administer Imodium to a dog suspected of ingesting poison. The Food and Drug Administration has not approved its use in veterinary medicine, as of 2015.