Loperamide, also referred to as Imodium, is sometimes recommended in veterinary practice to treat dogs for diarrhea.
Despite it’s safety in many canines, there are particular breeds of dogs that are sensitive to this drug class due to a genetic mutation (referred to as MDR1). Toxicosis may occur in these dogs even when therapeutic amounts are ingested. Dogs that are classified with this sensitivity include Australian Shepherds, Collies, English Shepherds, German Shepherds, Longhaired Whippets, McNabs, Old English Sheepdogs, Shetland Sheepdogs, and Silken Windhounds.
Signs and symptoms of toxicity: Clinical signs of neurological toxicity include fatigue, difficulty walking, increased saliva production, dilated pupils, blindness and seizures.
It is important to note that each animals’ reaction to medication will vary and thus the dosages at which animals have shown clinical signs of toxicity will also differ. Always follow your veterinarian’s directions for dosing.
At common doses used to treat diarrhea, toxicosis has been seen in dogs with the MDR1 mutation. Any level of consumption in these dogs should be reported immediately.
Problem Drugs. Washington State University College of Veterinary Medicine. Available at: http://www.vetmed.wsu.edu/depts-VCPL/drugs.aspx. Accessed March 15, 2015.