Medication for Dogs With Diarrhea

Diarrhea refers to rapid movement of digested material through a dog's gastrointestinal system. It causes more frequent bowel movements, which may be large or watery. While diarrhea often clears up on its own, severe cases can lead to dehydration and malnutrition and signal a serious underlying condition.
Dr. Shawn Messonier, DVM, says diarrhea can stem from stress, parasites, inflammatory bowel disease, cancer, viruses, pancreatitis or diet. The only way to determine its cause is with a veterinary exam. Several prescription and alternative medications can be used to treat diarrhea.

Parasite Medications for Diarrhea

Anthelmintic medications are prescribed for dogs with diarrhea resulting from worm infestations. Most of these medications work on only one or two varieties of worms, so diagnosing the animal's parasites correctly is essential. They usually require multiple treatments over a course of days, or single treatments separated by a few weeks.
Common worm medications are pyrantel, fentebel, fendendazole and nitroscanate.

Protozoa Medications for Diarrhea

Coccidia and giardia, forms of protozoa, can infiltrate a dog's digestive tract and cause diarrhea. Coccidia is treated with sulfa-based antibiotics.
While there's no specific medication to treat giardia, the anthelmintic fenbendazole and the antibiotic metronidazole are often prescribed.
A 1987 study at the University of Alberta Department of Pediatrics found that combining metronidazole and quinacrine hydrochloride treated giardiasis in humans more effectively than using them separately.

Antibiotics for Diarrhea

The bacteria clostridia, E. coli, salmonella, and campylobacter often cause diarrhea and vomiting in kenneled dogs or those with compromised immune systems. They are treated with a course of antibiotics.
Diarrhea resulting from ulcerative colitis requires long-term antibiotic use.

Enzymes and Anti-inflammatory Medications

When a dog's diarrhea results from endocrine pancreatic insufficiency, his pancreas isn't producing enough enzymes to properly digest his food. Pancreatic enzymes are a standard treatment, along with antibiotics to keep bacteria in check.
Messonier says dogs with inflammatory bowel disease may have damage to their enzyme-secreting and nutrient-absorbing intestinal cells. Adding enzymes to their food will increase its digestibility until their intestines heal. He prefers plant to pancreatic enzymes. Dogs with IBD-related diarrhea also benefit from anti-inflammatory drugs.

Over-the-Counter Diarrhea Medications

Bismuth subsalicylate, better known as Pepto-Bismol, can relieve diarrhea occuring after a dog eats something which has upset her stomach but isn't otherwise a serious danger. If it doesn't work within two days, a visit to the vet is in order.
Because it's sold in different strengths, a vet should prescribe the dosage.