Dogs can take Pepto-Bismol. It is one of a handful of over-the-counter medications which are designed for human use and also safe for dogs. The main concern with giving a dog Pepto-Bismol is drug interactions, especially with aspirin, as one of the active ingredients of Pepto-Bismol reinforces aspirin's side effects.
One teaspoon of Pepto-Bismol for every 20 pounds of body-weight is an effective and safe dosage for dogs with upset stomachs and diarrhea, explains Walker Valley Veterinarian Hospital in New York, NY.
Dogs with bleeding disorders, blood that does not clot properly, or allergies to aspirin must not be given Pepto-Bismol under any circumstances. The technical name for Pepto-Bismol is bismuth subsalicylate; the salicylate component is very similar to aspirin, and like aspirin can cause blood thinning and bleeding. This can affect healthy dogs, who become sick and are given both Pepto-Bismol and aspirin to treat symptoms of stomach upset and pain.